| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Alexei Starovoitov | 14777 | 53.17% | 65 | 28.76% |
| Edward Cree | 4740 | 17.05% | 10 | 4.42% |
| Daniel Borkmann | 3780 | 13.60% | 52 | 23.01% |
| Jakub Kiciński | 1096 | 3.94% | 18 | 7.96% |
| David S. Miller | 785 | 2.82% | 9 | 3.98% |
| Yonghong Song | 529 | 1.90% | 8 | 3.54% |
| Josef Bacik | 478 | 1.72% | 3 | 1.33% |
| Gianluca Borello | 325 | 1.17% | 6 | 2.65% |
| Martin KaFai Lau | 237 | 0.85% | 9 | 3.98% |
| Thomas Graf | 202 | 0.73% | 3 | 1.33% |
| Jiong Wang | 156 | 0.56% | 3 | 1.33% |
| Roman Gushchin | 145 | 0.52% | 4 | 1.77% |
| John Fastabend | 131 | 0.47% | 8 | 3.54% |
| Jiri Olsa | 84 | 0.30% | 1 | 0.44% |
| Brenden Blanco | 57 | 0.21% | 1 | 0.44% |
| Xia Kaixu | 44 | 0.16% | 1 | 0.44% |
| Quentin Monnet | 34 | 0.12% | 1 | 0.44% |
| Sandipan Das | 26 | 0.09% | 2 | 0.88% |
| Jann Horn | 25 | 0.09% | 2 | 0.88% |
| Rabin Vincent | 25 | 0.09% | 1 | 0.44% |
| Jesper Dangaard Brouer | 19 | 0.07% | 2 | 0.88% |
| Andrey Ignatov | 15 | 0.05% | 2 | 0.88% |
| Arthur Fabre | 14 | 0.05% | 1 | 0.44% |
| Arnd Bergmann | 14 | 0.05% | 1 | 0.44% |
| Kees Cook | 14 | 0.05% | 2 | 0.88% |
| Björn Töpel | 10 | 0.04% | 1 | 0.44% |
| Craig Gallek | 8 | 0.03% | 1 | 0.44% |
| Sargun Dhillon | 7 | 0.03% | 1 | 0.44% |
| Paul Chaignon | 6 | 0.02% | 1 | 0.44% |
| Colin Ian King | 5 | 0.02% | 4 | 1.77% |
| Mathieu Xhonneux | 3 | 0.01% | 1 | 0.44% |
| Alex Gartrell | 1 | 0.00% | 1 | 0.44% |
| Alexander Alemayhu | 1 | 0.00% | 1 | 0.44% |
| Total | 27793 | 226 |
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com * Copyright (c) 2016 Facebook * * This program is free software; you can redistribute it and/or * modify it under the terms of version 2 of the GNU General Public * License as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. */ #include <linux/kernel.h> #include <linux/types.h> #include <linux/slab.h> #include <linux/bpf.h> #include <linux/bpf_verifier.h> #include <linux/filter.h> #include <net/netlink.h> #include <linux/file.h> #include <linux/vmalloc.h> #include <linux/stringify.h> #include <linux/bsearch.h> #include <linux/sort.h> #include <linux/perf_event.h> #include "disasm.h" static const struct bpf_verifier_ops * const bpf_verifier_ops[] = { #define BPF_PROG_TYPE(_id, _name) \ [_id] = & _name ## _verifier_ops, #define BPF_MAP_TYPE(_id, _ops) #include <linux/bpf_types.h> #undef BPF_PROG_TYPE #undef BPF_MAP_TYPE }; /* bpf_check() is a static code analyzer that walks eBPF program * instruction by instruction and updates register/stack state. * All paths of conditional branches are analyzed until 'bpf_exit' insn. * * The first pass is depth-first-search to check that the program is a DAG. * It rejects the following programs: * - larger than BPF_MAXINSNS insns * - if loop is present (detected via back-edge) * - unreachable insns exist (shouldn't be a forest. program = one function) * - out of bounds or malformed jumps * The second pass is all possible path descent from the 1st insn. * Since it's analyzing all pathes through the program, the length of the * analysis is limited to 64k insn, which may be hit even if total number of * insn is less then 4K, but there are too many branches that change stack/regs. * Number of 'branches to be analyzed' is limited to 1k * * On entry to each instruction, each register has a type, and the instruction * changes the types of the registers depending on instruction semantics. * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is * copied to R1. * * All registers are 64-bit. * R0 - return register * R1-R5 argument passing registers * R6-R9 callee saved registers * R10 - frame pointer read-only * * At the start of BPF program the register R1 contains a pointer to bpf_context * and has type PTR_TO_CTX. * * Verifier tracks arithmetic operations on pointers in case: * BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), * BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20), * 1st insn copies R10 (which has FRAME_PTR) type into R1 * and 2nd arithmetic instruction is pattern matched to recognize * that it wants to construct a pointer to some element within stack. * So after 2nd insn, the register R1 has type PTR_TO_STACK * (and -20 constant is saved for further stack bounds checking). * Meaning that this reg is a pointer to stack plus known immediate constant. * * Most of the time the registers have SCALAR_VALUE type, which * means the register has some value, but it's not a valid pointer. * (like pointer plus pointer becomes SCALAR_VALUE type) * * When verifier sees load or store instructions the type of base register * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, PTR_TO_STACK. These are three pointer * types recognized by check_mem_access() function. * * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value' * and the range of [ptr, ptr + map's value_size) is accessible. * * registers used to pass values to function calls are checked against * function argument constraints. * * ARG_PTR_TO_MAP_KEY is one of such argument constraints. * It means that the register type passed to this function must be * PTR_TO_STACK and it will be used inside the function as * 'pointer to map element key' * * For example the argument constraints for bpf_map_lookup_elem(): * .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, * .arg1_type = ARG_CONST_MAP_PTR, * .arg2_type = ARG_PTR_TO_MAP_KEY, * * ret_type says that this function returns 'pointer to map elem value or null' * function expects 1st argument to be a const pointer to 'struct bpf_map' and * 2nd argument should be a pointer to stack, which will be used inside * the helper function as a pointer to map element key. * * On the kernel side the helper function looks like: * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) * { * struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; * void *key = (void *) (unsigned long) r2; * void *value; * * here kernel can access 'key' and 'map' pointers safely, knowing that * [key, key + map->key_size) bytes are valid and were initialized on * the stack of eBPF program. * } * * Corresponding eBPF program may look like: * BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR * BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK * BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP * BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), * here verifier looks at prototype of map_lookup_elem() and sees: * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok, * Now verifier knows that this map has key of R1->map_ptr->key_size bytes * * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far, * Now verifier checks that [R2, R2 + map's key_size) are within stack limits * and were initialized prior to this call. * If it's ok, then verifier allows this BPF_CALL insn and looks at * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function * returns ether pointer to map value or NULL. * * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off' * insn, the register holding that pointer in the true branch changes state to * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false * branch. See check_cond_jmp_op(). * * After the call R0 is set to return type of the function and registers R1-R5 * are set to NOT_INIT to indicate that they are no longer readable. */ /* verifier_state + insn_idx are pushed to stack when branch is encountered */ struct bpf_verifier_stack_elem { /* verifer state is 'st' * before processing instruction 'insn_idx' * and after processing instruction 'prev_insn_idx' */ struct bpf_verifier_state st; int insn_idx; int prev_insn_idx; struct bpf_verifier_stack_elem *next; }; #define BPF_COMPLEXITY_LIMIT_INSNS 131072 #define BPF_COMPLEXITY_LIMIT_STACK 1024 #define BPF_MAP_PTR_UNPRIV 1UL #define BPF_MAP_PTR_POISON ((void *)((0xeB9FUL << 1) + \ POISON_POINTER_DELTA)) #define BPF_MAP_PTR(X) ((struct bpf_map *)((X) & ~BPF_MAP_PTR_UNPRIV)) static bool bpf_map_ptr_poisoned(const struct bpf_insn_aux_data *aux) { return BPF_MAP_PTR(aux->map_state) == BPF_MAP_PTR_POISON; } static bool bpf_map_ptr_unpriv(const struct bpf_insn_aux_data *aux) { return aux->map_state & BPF_MAP_PTR_UNPRIV; } static void bpf_map_ptr_store(struct bpf_insn_aux_data *aux, const struct bpf_map *map, bool unpriv) { BUILD_BUG_ON((unsigned long)BPF_MAP_PTR_POISON & BPF_MAP_PTR_UNPRIV); unpriv |= bpf_map_ptr_unpriv(aux); aux->map_state = (unsigned long)map | (unpriv ? BPF_MAP_PTR_UNPRIV : 0UL); } struct bpf_call_arg_meta { struct bpf_map *map_ptr; bool raw_mode; bool pkt_access; int regno; int access_size; s64 msize_smax_value; u64 msize_umax_value; }; static DEFINE_MUTEX(bpf_verifier_lock); void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt, va_list args) { unsigned int n; n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args); WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1, "verifier log line truncated - local buffer too short\n"); n = min(log->len_total - log->len_used - 1, n); log->kbuf[n] = '\0'; if (!copy_to_user(log->ubuf + log->len_used, log->kbuf, n + 1)) log->len_used += n; else log->ubuf = NULL; } /* log_level controls verbosity level of eBPF verifier. * bpf_verifier_log_write() is used to dump the verification trace to the log, * so the user can figure out what's wrong with the program */ __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env, const char *fmt, ...) { va_list args; if (!bpf_verifier_log_needed(&env->log)) return; va_start(args, fmt); bpf_verifier_vlog(&env->log, fmt, args); va_end(args); } EXPORT_SYMBOL_GPL(bpf_verifier_log_write); __printf(2, 3) static void verbose(void *private_data, const char *fmt, ...) { struct bpf_verifier_env *env = private_data; va_list args; if (!bpf_verifier_log_needed(&env->log)) return; va_start(args, fmt); bpf_verifier_vlog(&env->log, fmt, args); va_end(args); } static bool type_is_pkt_pointer(enum bpf_reg_type type) { return type == PTR_TO_PACKET || type == PTR_TO_PACKET_META; } /* string representation of 'enum bpf_reg_type' */ static const char * const reg_type_str[] = { [NOT_INIT] = "?", [SCALAR_VALUE] = "inv", [PTR_TO_CTX] = "ctx", [CONST_PTR_TO_MAP] = "map_ptr", [PTR_TO_MAP_VALUE] = "map_value", [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null", [PTR_TO_STACK] = "fp", [PTR_TO_PACKET] = "pkt", [PTR_TO_PACKET_META] = "pkt_meta", [PTR_TO_PACKET_END] = "pkt_end", }; static void print_liveness(struct bpf_verifier_env *env, enum bpf_reg_liveness live) { if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN)) verbose(env, "_"); if (live & REG_LIVE_READ) verbose(env, "r"); if (live & REG_LIVE_WRITTEN) verbose(env, "w"); } static struct bpf_func_state *func(struct bpf_verifier_env *env, const struct bpf_reg_state *reg) { struct bpf_verifier_state *cur = env->cur_state; return cur->frame[reg->frameno]; } static void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_func_state *state) { const struct bpf_reg_state *reg; enum bpf_reg_type t; int i; if (state->frameno) verbose(env, " frame%d:", state->frameno); for (i = 0; i < MAX_BPF_REG; i++) { reg = &state->regs[i]; t = reg->type; if (t == NOT_INIT) continue; verbose(env, " R%d", i); print_liveness(env, reg->live); verbose(env, "=%s", reg_type_str[t]); if ((t == SCALAR_VALUE || t == PTR_TO_STACK) && tnum_is_const(reg->var_off)) { /* reg->off should be 0 for SCALAR_VALUE */ verbose(env, "%lld", reg->var_off.value + reg->off); if (t == PTR_TO_STACK) verbose(env, ",call_%d", func(env, reg)->callsite); } else { verbose(env, "(id=%d", reg->id); if (t != SCALAR_VALUE) verbose(env, ",off=%d", reg->off); if (type_is_pkt_pointer(t)) verbose(env, ",r=%d", reg->range); else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE || t == PTR_TO_MAP_VALUE_OR_NULL) verbose(env, ",ks=%d,vs=%d", reg->map_ptr->key_size, reg->map_ptr->value_size); if (tnum_is_const(reg->var_off)) { /* Typically an immediate SCALAR_VALUE, but * could be a pointer whose offset is too big * for reg->off */ verbose(env, ",imm=%llx", reg->var_off.value); } else { if (reg->smin_value != reg->umin_value && reg->smin_value != S64_MIN) verbose(env, ",smin_value=%lld", (long long)reg->smin_value); if (reg->smax_value != reg->umax_value && reg->smax_value != S64_MAX) verbose(env, ",smax_value=%lld", (long long)reg->smax_value); if (reg->umin_value != 0) verbose(env, ",umin_value=%llu", (unsigned long long)reg->umin_value); if (reg->umax_value != U64_MAX) verbose(env, ",umax_value=%llu", (unsigned long long)reg->umax_value); if (!tnum_is_unknown(reg->var_off)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, ",var_off=%s", tn_buf); } } verbose(env, ")"); } } for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) { if (state->stack[i].slot_type[0] == STACK_SPILL) { verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE); print_liveness(env, state->stack[i].spilled_ptr.live); verbose(env, "=%s", reg_type_str[state->stack[i].spilled_ptr.type]); } if (state->stack[i].slot_type[0] == STACK_ZERO) verbose(env, " fp%d=0", (-i - 1) * BPF_REG_SIZE); } verbose(env, "\n"); } static int copy_stack_state(struct bpf_func_state *dst, const struct bpf_func_state *src) { if (!src->stack) return 0; if (WARN_ON_ONCE(dst->allocated_stack < src->allocated_stack)) { /* internal bug, make state invalid to reject the program */ memset(dst, 0, sizeof(*dst)); return -EFAULT; } memcpy(dst->stack, src->stack, sizeof(*src->stack) * (src->allocated_stack / BPF_REG_SIZE)); return 0; } /* do_check() starts with zero-sized stack in struct bpf_verifier_state to * make it consume minimal amount of memory. check_stack_write() access from * the program calls into realloc_func_state() to grow the stack size. * Note there is a non-zero 'parent' pointer inside bpf_verifier_state * which this function copies over. It points to previous bpf_verifier_state * which is never reallocated */ static int realloc_func_state(struct bpf_func_state *state, int size, bool copy_old) { u32 old_size = state->allocated_stack; struct bpf_stack_state *new_stack; int slot = size / BPF_REG_SIZE; if (size <= old_size || !size) { if (copy_old) return 0; state->allocated_stack = slot * BPF_REG_SIZE; if (!size && old_size) { kfree(state->stack); state->stack = NULL; } return 0; } new_stack = kmalloc_array(slot, sizeof(struct bpf_stack_state), GFP_KERNEL); if (!new_stack) return -ENOMEM; if (copy_old) { if (state->stack) memcpy(new_stack, state->stack, sizeof(*new_stack) * (old_size / BPF_REG_SIZE)); memset(new_stack + old_size / BPF_REG_SIZE, 0, sizeof(*new_stack) * (size - old_size) / BPF_REG_SIZE); } state->allocated_stack = slot * BPF_REG_SIZE; kfree(state->stack); state->stack = new_stack; return 0; } static void free_func_state(struct bpf_func_state *state) { if (!state) return; kfree(state->stack); kfree(state); } static void free_verifier_state(struct bpf_verifier_state *state, bool free_self) { int i; for (i = 0; i <= state->curframe; i++) { free_func_state(state->frame[i]); state->frame[i] = NULL; } if (free_self) kfree(state); } /* copy verifier state from src to dst growing dst stack space * when necessary to accommodate larger src stack */ static int copy_func_state(struct bpf_func_state *dst, const struct bpf_func_state *src) { int err; err = realloc_func_state(dst, src->allocated_stack, false); if (err) return err; memcpy(dst, src, offsetof(struct bpf_func_state, allocated_stack)); return copy_stack_state(dst, src); } static int copy_verifier_state(struct bpf_verifier_state *dst_state, const struct bpf_verifier_state *src) { struct bpf_func_state *dst; int i, err; /* if dst has more stack frames then src frame, free them */ for (i = src->curframe + 1; i <= dst_state->curframe; i++) { free_func_state(dst_state->frame[i]); dst_state->frame[i] = NULL; } dst_state->curframe = src->curframe; dst_state->parent = src->parent; for (i = 0; i <= src->curframe; i++) { dst = dst_state->frame[i]; if (!dst) { dst = kzalloc(sizeof(*dst), GFP_KERNEL); if (!dst) return -ENOMEM; dst_state->frame[i] = dst; } err = copy_func_state(dst, src->frame[i]); if (err) return err; } return 0; } static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx, int *insn_idx) { struct bpf_verifier_state *cur = env->cur_state; struct bpf_verifier_stack_elem *elem, *head = env->head; int err; if (env->head == NULL) return -ENOENT; if (cur) { err = copy_verifier_state(cur, &head->st); if (err) return err; } if (insn_idx) *insn_idx = head->insn_idx; if (prev_insn_idx) *prev_insn_idx = head->prev_insn_idx; elem = head->next; free_verifier_state(&head->st, false); kfree(head); env->head = elem; env->stack_size--; return 0; } static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx) { struct bpf_verifier_state *cur = env->cur_state; struct bpf_verifier_stack_elem *elem; int err; elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL); if (!elem) goto err; elem->insn_idx = insn_idx; elem->prev_insn_idx = prev_insn_idx; elem->next = env->head; env->head = elem; env->stack_size++; err = copy_verifier_state(&elem->st, cur); if (err) goto err; if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) { verbose(env, "BPF program is too complex\n"); goto err; } return &elem->st; err: free_verifier_state(env->cur_state, true); env->cur_state = NULL; /* pop all elements and return */ while (!pop_stack(env, NULL, NULL)); return NULL; } #define CALLER_SAVED_REGS 6 static const int caller_saved[CALLER_SAVED_REGS] = { BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5 }; static void __mark_reg_not_init(struct bpf_reg_state *reg); /* Mark the unknown part of a register (variable offset or scalar value) as * known to have the value @imm. */ static void __mark_reg_known(struct bpf_reg_state *reg, u64 imm) { reg->id = 0; reg->var_off = tnum_const(imm); reg->smin_value = (s64)imm; reg->smax_value = (s64)imm; reg->umin_value = imm; reg->umax_value = imm; } /* Mark the 'variable offset' part of a register as zero. This should be * used only on registers holding a pointer type. */ static void __mark_reg_known_zero(struct bpf_reg_state *reg) { __mark_reg_known(reg, 0); } static void __mark_reg_const_zero(struct bpf_reg_state *reg) { __mark_reg_known(reg, 0); reg->off = 0; reg->type = SCALAR_VALUE; } static void mark_reg_known_zero(struct bpf_verifier_env *env, struct bpf_reg_state *regs, u32 regno) { if (WARN_ON(regno >= MAX_BPF_REG)) { verbose(env, "mark_reg_known_zero(regs, %u)\n", regno); /* Something bad happened, let's kill all regs */ for (regno = 0; regno < MAX_BPF_REG; regno++) __mark_reg_not_init(regs + regno); return; } __mark_reg_known_zero(regs + regno); } static bool reg_is_pkt_pointer(const struct bpf_reg_state *reg) { return type_is_pkt_pointer(reg->type); } static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg) { return reg_is_pkt_pointer(reg) || reg->type == PTR_TO_PACKET_END; } /* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */ static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg, enum bpf_reg_type which) { /* The register can already have a range from prior markings. * This is fine as long as it hasn't been advanced from its * origin. */ return reg->type == which && reg->id == 0 && reg->off == 0 && tnum_equals_const(reg->var_off, 0); } /* Attempts to improve min/max values based on var_off information */ static void __update_reg_bounds(struct bpf_reg_state *reg) { /* min signed is max(sign bit) | min(other bits) */ reg->smin_value = max_t(s64, reg->smin_value, reg->var_off.value | (reg->var_off.mask & S64_MIN)); /* max signed is min(sign bit) | max(other bits) */ reg->smax_value = min_t(s64, reg->smax_value, reg->var_off.value | (reg->var_off.mask & S64_MAX)); reg->umin_value = max(reg->umin_value, reg->var_off.value); reg->umax_value = min(reg->umax_value, reg->var_off.value | reg->var_off.mask); } /* Uses signed min/max values to inform unsigned, and vice-versa */ static void __reg_deduce_bounds(struct bpf_reg_state *reg) { /* Learn sign from signed bounds. * If we cannot cross the sign boundary, then signed and unsigned bounds * are the same, so combine. This works even in the negative case, e.g. * -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff. */ if (reg->smin_value >= 0 || reg->smax_value < 0) { reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value, reg->umin_value); reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value, reg->umax_value); return; } /* Learn sign from unsigned bounds. Signed bounds cross the sign * boundary, so we must be careful. */ if ((s64)reg->umax_value >= 0) { /* Positive. We can't learn anything from the smin, but smax * is positive, hence safe. */ reg->smin_value = reg->umin_value; reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value, reg->umax_value); } else if ((s64)reg->umin_value < 0) { /* Negative. We can't learn anything from the smax, but smin * is negative, hence safe. */ reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value, reg->umin_value); reg->smax_value = reg->umax_value; } } /* Attempts to improve var_off based on unsigned min/max information */ static void __reg_bound_offset(struct bpf_reg_state *reg) { reg->var_off = tnum_intersect(reg->var_off, tnum_range(reg->umin_value, reg->umax_value)); } /* Reset the min/max bounds of a register */ static void __mark_reg_unbounded(struct bpf_reg_state *reg) { reg->smin_value = S64_MIN; reg->smax_value = S64_MAX; reg->umin_value = 0; reg->umax_value = U64_MAX; } /* Mark a register as having a completely unknown (scalar) value. */ static void __mark_reg_unknown(struct bpf_reg_state *reg) { reg->type = SCALAR_VALUE; reg->id = 0; reg->off = 0; reg->var_off = tnum_unknown; reg->frameno = 0; __mark_reg_unbounded(reg); } static void mark_reg_unknown(struct bpf_verifier_env *env, struct bpf_reg_state *regs, u32 regno) { if (WARN_ON(regno >= MAX_BPF_REG)) { verbose(env, "mark_reg_unknown(regs, %u)\n", regno); /* Something bad happened, let's kill all regs except FP */ for (regno = 0; regno < BPF_REG_FP; regno++) __mark_reg_not_init(regs + regno); return; } __mark_reg_unknown(regs + regno); } static void __mark_reg_not_init(struct bpf_reg_state *reg) { __mark_reg_unknown(reg); reg->type = NOT_INIT; } static void mark_reg_not_init(struct bpf_verifier_env *env, struct bpf_reg_state *regs, u32 regno) { if (WARN_ON(regno >= MAX_BPF_REG)) { verbose(env, "mark_reg_not_init(regs, %u)\n", regno); /* Something bad happened, let's kill all regs except FP */ for (regno = 0; regno < BPF_REG_FP; regno++) __mark_reg_not_init(regs + regno); return; } __mark_reg_not_init(regs + regno); } static void init_reg_state(struct bpf_verifier_env *env, struct bpf_func_state *state) { struct bpf_reg_state *regs = state->regs; int i; for (i = 0; i < MAX_BPF_REG; i++) { mark_reg_not_init(env, regs, i); regs[i].live = REG_LIVE_NONE; } /* frame pointer */ regs[BPF_REG_FP].type = PTR_TO_STACK; mark_reg_known_zero(env, regs, BPF_REG_FP); regs[BPF_REG_FP].frameno = state->frameno; /* 1st arg to a function */ regs[BPF_REG_1].type = PTR_TO_CTX; mark_reg_known_zero(env, regs, BPF_REG_1); } #define BPF_MAIN_FUNC (-1) static void init_func_state(struct bpf_verifier_env *env, struct bpf_func_state *state, int callsite, int frameno, int subprogno) { state->callsite = callsite; state->frameno = frameno; state->subprogno = subprogno; init_reg_state(env, state); } enum reg_arg_type { SRC_OP, /* register is used as source operand */ DST_OP, /* register is used as destination operand */ DST_OP_NO_MARK /* same as above, check only, don't mark */ }; static int cmp_subprogs(const void *a, const void *b) { return ((struct bpf_subprog_info *)a)->start - ((struct bpf_subprog_info *)b)->start; } static int find_subprog(struct bpf_verifier_env *env, int off) { struct bpf_subprog_info *p; p = bsearch(&off, env->subprog_info, env->subprog_cnt, sizeof(env->subprog_info[0]), cmp_subprogs); if (!p) return -ENOENT; return p - env->subprog_info; } static int add_subprog(struct bpf_verifier_env *env, int off) { int insn_cnt = env->prog->len; int ret; if (off >= insn_cnt || off < 0) { verbose(env, "call to invalid destination\n"); return -EINVAL; } ret = find_subprog(env, off); if (ret >= 0) return 0; if (env->subprog_cnt >= BPF_MAX_SUBPROGS) { verbose(env, "too many subprograms\n"); return -E2BIG; } env->subprog_info[env->subprog_cnt++].start = off; sort(env->subprog_info, env->subprog_cnt, sizeof(env->subprog_info[0]), cmp_subprogs, NULL); return 0; } static int check_subprogs(struct bpf_verifier_env *env) { int i, ret, subprog_start, subprog_end, off, cur_subprog = 0; struct bpf_subprog_info *subprog = env->subprog_info; struct bpf_insn *insn = env->prog->insnsi; int insn_cnt = env->prog->len; /* Add entry function. */ ret = add_subprog(env, 0); if (ret < 0) return ret; /* determine subprog starts. The end is one before the next starts */ for (i = 0; i < insn_cnt; i++) { if (insn[i].code != (BPF_JMP | BPF_CALL)) continue; if (insn[i].src_reg != BPF_PSEUDO_CALL) continue; if (!env->allow_ptr_leaks) { verbose(env, "function calls to other bpf functions are allowed for root only\n"); return -EPERM; } if (bpf_prog_is_dev_bound(env->prog->aux)) { verbose(env, "function calls in offloaded programs are not supported yet\n"); return -EINVAL; } ret = add_subprog(env, i + insn[i].imm + 1); if (ret < 0) return ret; } /* Add a fake 'exit' subprog which could simplify subprog iteration * logic. 'subprog_cnt' should not be increased. */ subprog[env->subprog_cnt].start = insn_cnt; if (env->log.level > 1) for (i = 0; i < env->subprog_cnt; i++) verbose(env, "func#%d @%d\n", i, subprog[i].start); /* now check that all jumps are within the same subprog */ subprog_start = subprog[cur_subprog].start; subprog_end = subprog[cur_subprog + 1].start; for (i = 0; i < insn_cnt; i++) { u8 code = insn[i].code; if (BPF_CLASS(code) != BPF_JMP) goto next; if (BPF_OP(code) == BPF_EXIT || BPF_OP(code) == BPF_CALL) goto next; off = i + insn[i].off + 1; if (off < subprog_start || off >= subprog_end) { verbose(env, "jump out of range from insn %d to %d\n", i, off); return -EINVAL; } next: if (i == subprog_end - 1) { /* to avoid fall-through from one subprog into another * the last insn of the subprog should be either exit * or unconditional jump back */ if (code != (BPF_JMP | BPF_EXIT) && code != (BPF_JMP | BPF_JA)) { verbose(env, "last insn is not an exit or jmp\n"); return -EINVAL; } subprog_start = subprog_end; cur_subprog++; if (cur_subprog < env->subprog_cnt) subprog_end = subprog[cur_subprog + 1].start; } } return 0; } static struct bpf_verifier_state *skip_callee(struct bpf_verifier_env *env, const struct bpf_verifier_state *state, struct bpf_verifier_state *parent, u32 regno) { struct bpf_verifier_state *tmp = NULL; /* 'parent' could be a state of caller and * 'state' could be a state of callee. In such case * parent->curframe < state->curframe * and it's ok for r1 - r5 registers * * 'parent' could be a callee's state after it bpf_exit-ed. * In such case parent->curframe > state->curframe * and it's ok for r0 only */ if (parent->curframe == state->curframe || (parent->curframe < state->curframe && regno >= BPF_REG_1 && regno <= BPF_REG_5) || (parent->curframe > state->curframe && regno == BPF_REG_0)) return parent; if (parent->curframe > state->curframe && regno >= BPF_REG_6) { /* for callee saved regs we have to skip the whole chain * of states that belong to callee and mark as LIVE_READ * the registers before the call */ tmp = parent; while (tmp && tmp->curframe != state->curframe) { tmp = tmp->parent; } if (!tmp) goto bug; parent = tmp; } else { goto bug; } return parent; bug: verbose(env, "verifier bug regno %d tmp %p\n", regno, tmp); verbose(env, "regno %d parent frame %d current frame %d\n", regno, parent->curframe, state->curframe); return NULL; } static int mark_reg_read(struct bpf_verifier_env *env, const struct bpf_verifier_state *state, struct bpf_verifier_state *parent, u32 regno) { bool writes = parent == state->parent; /* Observe write marks */ if (regno == BPF_REG_FP) /* We don't need to worry about FP liveness because it's read-only */ return 0; while (parent) { /* if read wasn't screened by an earlier write ... */ if (writes && state->frame[state->curframe]->regs[regno].live & REG_LIVE_WRITTEN) break; parent = skip_callee(env, state, parent, regno); if (!parent) return -EFAULT; /* ... then we depend on parent's value */ parent->frame[parent->curframe]->regs[regno].live |= REG_LIVE_READ; state = parent; parent = state->parent; writes = true; } return 0; } static int check_reg_arg(struct bpf_verifier_env *env, u32 regno, enum reg_arg_type t) { struct bpf_verifier_state *vstate = env->cur_state; struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *regs = state->regs; if (regno >= MAX_BPF_REG) { verbose(env, "R%d is invalid\n", regno); return -EINVAL; } if (t == SRC_OP) { /* check whether register used as source operand can be read */ if (regs[regno].type == NOT_INIT) { verbose(env, "R%d !read_ok\n", regno); return -EACCES; } return mark_reg_read(env, vstate, vstate->parent, regno); } else { /* check whether register used as dest operand can be written to */ if (regno == BPF_REG_FP) { verbose(env, "frame pointer is read only\n"); return -EACCES; } regs[regno].live |= REG_LIVE_WRITTEN; if (t == DST_OP) mark_reg_unknown(env, regs, regno); } return 0; } static bool is_spillable_regtype(enum bpf_reg_type type) { switch (type) { case PTR_TO_MAP_VALUE: case PTR_TO_MAP_VALUE_OR_NULL: case PTR_TO_STACK: case PTR_TO_CTX: case PTR_TO_PACKET: case PTR_TO_PACKET_META: case PTR_TO_PACKET_END: case CONST_PTR_TO_MAP: return true; default: return false; } } /* Does this register contain a constant zero? */ static bool register_is_null(struct bpf_reg_state *reg) { return reg->type == SCALAR_VALUE && tnum_equals_const(reg->var_off, 0); } /* check_stack_read/write functions track spill/fill of registers, * stack boundary and alignment are checked in check_mem_access() */ static int check_stack_write(struct bpf_verifier_env *env, struct bpf_func_state *state, /* func where register points to */ int off, int size, int value_regno, int insn_idx) { struct bpf_func_state *cur; /* state of the current function */ int i, slot = -off - 1, spi = slot / BPF_REG_SIZE, err; enum bpf_reg_type type; err = realloc_func_state(state, round_up(slot + 1, BPF_REG_SIZE), true); if (err) return err; /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0, * so it's aligned access and [off, off + size) are within stack limits */ if (!env->allow_ptr_leaks && state->stack[spi].slot_type[0] == STACK_SPILL && size != BPF_REG_SIZE) { verbose(env, "attempt to corrupt spilled pointer on stack\n"); return -EACCES; } cur = env->cur_state->frame[env->cur_state->curframe]; if (value_regno >= 0 && is_spillable_regtype((type = cur->regs[value_regno].type))) { /* register containing pointer is being spilled into stack */ if (size != BPF_REG_SIZE) { verbose(env, "invalid size of register spill\n"); return -EACCES; } if (state != cur && type == PTR_TO_STACK) { verbose(env, "cannot spill pointers to stack into stack frame of the caller\n"); return -EINVAL; } /* save register state */ state->stack[spi].spilled_ptr = cur->regs[value_regno]; state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN; for (i = 0; i < BPF_REG_SIZE; i++) { if (state->stack[spi].slot_type[i] == STACK_MISC && !env->allow_ptr_leaks) { int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off; int soff = (-spi - 1) * BPF_REG_SIZE; /* detected reuse of integer stack slot with a pointer * which means either llvm is reusing stack slot or * an attacker is trying to exploit CVE-2018-3639 * (speculative store bypass) * Have to sanitize that slot with preemptive * store of zero. */ if (*poff && *poff != soff) { /* disallow programs where single insn stores * into two different stack slots, since verifier * cannot sanitize them */ verbose(env, "insn %d cannot access two stack slots fp%d and fp%d", insn_idx, *poff, soff); return -EINVAL; } *poff = soff; } state->stack[spi].slot_type[i] = STACK_SPILL; } } else { u8 type = STACK_MISC; /* regular write of data into stack */ state->stack[spi].spilled_ptr = (struct bpf_reg_state) {}; /* only mark the slot as written if all 8 bytes were written * otherwise read propagation may incorrectly stop too soon * when stack slots are partially written. * This heuristic means that read propagation will be * conservative, since it will add reg_live_read marks * to stack slots all the way to first state when programs * writes+reads less than 8 bytes */ if (size == BPF_REG_SIZE) state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN; /* when we zero initialize stack slots mark them as such */ if (value_regno >= 0 && register_is_null(&cur->regs[value_regno])) type = STACK_ZERO; for (i = 0; i < size; i++) state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] = type; } return 0; } /* registers of every function are unique and mark_reg_read() propagates * the liveness in the following cases: * - from callee into caller for R1 - R5 that were used as arguments * - from caller into callee for R0 that used as result of the call * - from caller to the same caller skipping states of the callee for R6 - R9, * since R6 - R9 are callee saved by implicit function prologue and * caller's R6 != callee's R6, so when we propagate liveness up to * parent states we need to skip callee states for R6 - R9. * * stack slot marking is different, since stacks of caller and callee are * accessible in both (since caller can pass a pointer to caller's stack to * callee which can pass it to another function), hence mark_stack_slot_read() * has to propagate the stack liveness to all parent states at given frame number. * Consider code: * f1() { * ptr = fp - 8; * *ptr = ctx; * call f2 { * .. = *ptr; * } * .. = *ptr; * } * First *ptr is reading from f1's stack and mark_stack_slot_read() has * to mark liveness at the f1's frame and not f2's frame. * Second *ptr is also reading from f1's stack and mark_stack_slot_read() has * to propagate liveness to f2 states at f1's frame level and further into * f1 states at f1's frame level until write into that stack slot */ static void mark_stack_slot_read(struct bpf_verifier_env *env, const struct bpf_verifier_state *state, struct bpf_verifier_state *parent, int slot, int frameno) { bool writes = parent == state->parent; /* Observe write marks */ while (parent) { if (parent->frame[frameno]->allocated_stack <= slot * BPF_REG_SIZE) /* since LIVE_WRITTEN mark is only done for full 8-byte * write the read marks are conservative and parent * state may not even have the stack allocated. In such case * end the propagation, since the loop reached beginning * of the function */ break; /* if read wasn't screened by an earlier write ... */ if (writes && state->frame[frameno]->stack[slot].spilled_ptr.live & REG_LIVE_WRITTEN) break; /* ... then we depend on parent's value */ parent->frame[frameno]->stack[slot].spilled_ptr.live |= REG_LIVE_READ; state = parent; parent = state->parent; writes = true; } } static int check_stack_read(struct bpf_verifier_env *env, struct bpf_func_state *reg_state /* func where register points to */, int off, int size, int value_regno) { struct bpf_verifier_state *vstate = env->cur_state; struct bpf_func_state *state = vstate->frame[vstate->curframe]; int i, slot = -off - 1, spi = slot / BPF_REG_SIZE; u8 *stype; if (reg_state->allocated_stack <= slot) { verbose(env, "invalid read from stack off %d+0 size %d\n", off, size); return -EACCES; } stype = reg_state->stack[spi].slot_type; if (stype[0] == STACK_SPILL) { if (size != BPF_REG_SIZE) { verbose(env, "invalid size of register spill\n"); return -EACCES; } for (i = 1; i < BPF_REG_SIZE; i++) { if (stype[(slot - i) % BPF_REG_SIZE] != STACK_SPILL) { verbose(env, "corrupted spill memory\n"); return -EACCES; } } if (value_regno >= 0) { /* restore register state from stack */ state->regs[value_regno] = reg_state->stack[spi].spilled_ptr; /* mark reg as written since spilled pointer state likely * has its liveness marks cleared by is_state_visited() * which resets stack/reg liveness for state transitions */ state->regs[value_regno].live |= REG_LIVE_WRITTEN; } mark_stack_slot_read(env, vstate, vstate->parent, spi, reg_state->frameno); return 0; } else { int zeros = 0; for (i = 0; i < size; i++) { if (stype[(slot - i) % BPF_REG_SIZE] == STACK_MISC) continue; if (stype[(slot - i) % BPF_REG_SIZE] == STACK_ZERO) { zeros++; continue; } verbose(env, "invalid read from stack off %d+%d size %d\n", off, i, size); return -EACCES; } mark_stack_slot_read(env, vstate, vstate->parent, spi, reg_state->frameno); if (value_regno >= 0) { if (zeros == size) { /* any size read into register is zero extended, * so the whole register == const_zero */ __mark_reg_const_zero(&state->regs[value_regno]); } else { /* have read misc data from the stack */ mark_reg_unknown(env, state->regs, value_regno); } state->regs[value_regno].live |= REG_LIVE_WRITTEN; } return 0; } } /* check read/write into map element returned by bpf_map_lookup_elem() */ static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off, int size, bool zero_size_allowed) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_map *map = regs[regno].map_ptr; if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) || off + size > map->value_size) { verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n", map->value_size, off, size); return -EACCES; } return 0; } /* check read/write into a map element with possible variable offset */ static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off, int size, bool zero_size_allowed) { struct bpf_verifier_state *vstate = env->cur_state; struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *reg = &state->regs[regno]; int err; /* We may have adjusted the register to this map value, so we * need to try adding each of min_value and max_value to off * to make sure our theoretical access will be safe. */ if (env->log.level) print_verifier_state(env, state); /* The minimum value is only important with signed * comparisons where we can't assume the floor of a * value is 0. If we are using signed variables for our * index'es we need to make sure that whatever we use * will have a set floor within our range. */ if (reg->smin_value < 0) { verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", regno); return -EACCES; } err = __check_map_access(env, regno, reg->smin_value + off, size, zero_size_allowed); if (err) { verbose(env, "R%d min value is outside of the array range\n", regno); return err; } /* If we haven't set a max value then we need to bail since we can't be * sure we won't do bad things. * If reg->umax_value + off could overflow, treat that as unbounded too. */ if (reg->umax_value >= BPF_MAX_VAR_OFF) { verbose(env, "R%d unbounded memory access, make sure to bounds check any array access into a map\n", regno); return -EACCES; } err = __check_map_access(env, regno, reg->umax_value + off, size, zero_size_allowed); if (err) verbose(env, "R%d max value is outside of the array range\n", regno); return err; } #define MAX_PACKET_OFF 0xffff static bool may_access_direct_pkt_data(struct bpf_verifier_env *env, const struct bpf_call_arg_meta *meta, enum bpf_access_type t) { switch (env->prog->type) { case BPF_PROG_TYPE_LWT_IN: case BPF_PROG_TYPE_LWT_OUT: case BPF_PROG_TYPE_LWT_SEG6LOCAL: case BPF_PROG_TYPE_SK_REUSEPORT: /* dst_input() and dst_output() can't write for now */ if (t == BPF_WRITE) return false; /* fallthrough */ case BPF_PROG_TYPE_SCHED_CLS: case BPF_PROG_TYPE_SCHED_ACT: case BPF_PROG_TYPE_XDP: case BPF_PROG_TYPE_LWT_XMIT: case BPF_PROG_TYPE_SK_SKB: case BPF_PROG_TYPE_SK_MSG: if (meta) return meta->pkt_access; env->seen_direct_write = true; return true; default: return false; } } static int __check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, int size, bool zero_size_allowed) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = ®s[regno]; if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) || (u64)off + size > reg->range) { verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n", off, size, regno, reg->id, reg->off, reg->range); return -EACCES; } return 0; } static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, int size, bool zero_size_allowed) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = ®s[regno]; int err; /* We may have added a variable offset to the packet pointer; but any * reg->range we have comes after that. We are only checking the fixed * offset. */ /* We don't allow negative numbers, because we aren't tracking enough * detail to prove they're safe. */ if (reg->smin_value < 0) { verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", regno); return -EACCES; } err = __check_packet_access(env, regno, off, size, zero_size_allowed); if (err) { verbose(env, "R%d offset is outside of the packet\n", regno); return err; } return err; } /* check access to 'struct bpf_context' fields. Supports fixed offsets only */ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type) { struct bpf_insn_access_aux info = { .reg_type = *reg_type, }; if (env->ops->is_valid_access && env->ops->is_valid_access(off, size, t, env->prog, &info)) { /* A non zero info.ctx_field_size indicates that this field is a * candidate for later verifier transformation to load the whole * field and then apply a mask when accessed with a narrower * access than actual ctx access size. A zero info.ctx_field_size * will only allow for whole field access and rejects any other * type of narrower access. */ *reg_type = info.reg_type; env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size; /* remember the offset of last byte accessed in ctx */ if (env->prog->aux->max_ctx_offset < off + size) env->prog->aux->max_ctx_offset = off + size; return 0; } verbose(env, "invalid bpf_context access off=%d size=%d\n", off, size); return -EACCES; } static bool __is_pointer_value(bool allow_ptr_leaks, const struct bpf_reg_state *reg) { if (allow_ptr_leaks) return false; return reg->type != SCALAR_VALUE; } static bool is_pointer_value(struct bpf_verifier_env *env, int regno) { return __is_pointer_value(env->allow_ptr_leaks, cur_regs(env) + regno); } static bool is_ctx_reg(struct bpf_verifier_env *env, int regno) { const struct bpf_reg_state *reg = cur_regs(env) + regno; return reg->type == PTR_TO_CTX; } static bool is_pkt_reg(struct bpf_verifier_env *env, int regno) { const struct bpf_reg_state *reg = cur_regs(env) + regno; return type_is_pkt_pointer(reg->type); } static int check_pkt_ptr_alignment(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, int off, int size, bool strict) { struct tnum reg_off; int ip_align; /* Byte size accesses are always allowed. */ if (!strict || size == 1) return 0; /* For platforms that do not have a Kconfig enabling * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of * NET_IP_ALIGN is universally set to '2'. And on platforms * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get * to this code only in strict mode where we want to emulate * the NET_IP_ALIGN==2 checking. Therefore use an * unconditional IP align value of '2'. */ ip_align = 2; reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off)); if (!tnum_is_aligned(reg_off, size)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "misaligned packet access off %d+%s+%d+%d size %d\n", ip_align, tn_buf, reg->off, off, size); return -EACCES; } return 0; } static int check_generic_ptr_alignment(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, const char *pointer_desc, int off, int size, bool strict) { struct tnum reg_off; /* Byte size accesses are always allowed. */ if (!strict || size == 1) return 0; reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off)); if (!tnum_is_aligned(reg_off, size)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "misaligned %saccess off %s+%d+%d size %d\n", pointer_desc, tn_buf, reg->off, off, size); return -EACCES; } return 0; } static int check_ptr_alignment(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, int off, int size, bool strict_alignment_once) { bool strict = env->strict_alignment || strict_alignment_once; const char *pointer_desc = ""; switch (reg->type) { case PTR_TO_PACKET: case PTR_TO_PACKET_META: /* Special case, because of NET_IP_ALIGN. Given metadata sits * right in front, treat it the very same way. */ return check_pkt_ptr_alignment(env, reg, off, size, strict); case PTR_TO_MAP_VALUE: pointer_desc = "value "; break; case PTR_TO_CTX: pointer_desc = "context "; break; case PTR_TO_STACK: pointer_desc = "stack "; /* The stack spill tracking logic in check_stack_write() * and check_stack_read() relies on stack accesses being * aligned. */ strict = true; break; default: break; } return check_generic_ptr_alignment(env, reg, pointer_desc, off, size, strict); } static int update_stack_depth(struct bpf_verifier_env *env, const struct bpf_func_state *func, int off) { u16 stack = env->subprog_info[func->subprogno].stack_depth; if (stack >= -off) return 0; /* update known max for given subprogram */ env->subprog_info[func->subprogno].stack_depth = -off; return 0; } /* starting from main bpf function walk all instructions of the function * and recursively walk all callees that given function can call. * Ignore jump and exit insns. * Since recursion is prevented by check_cfg() this algorithm * only needs a local stack of MAX_CALL_FRAMES to remember callsites */ static int check_max_stack_depth(struct bpf_verifier_env *env) { int depth = 0, frame = 0, idx = 0, i = 0, subprog_end; struct bpf_subprog_info *subprog = env->subprog_info; struct bpf_insn *insn = env->prog->insnsi; int ret_insn[MAX_CALL_FRAMES]; int ret_prog[MAX_CALL_FRAMES]; process_func: /* round up to 32-bytes, since this is granularity * of interpreter stack size */ depth += round_up(max_t(u32, subprog[idx].stack_depth, 1), 32); if (depth > MAX_BPF_STACK) { verbose(env, "combined stack size of %d calls is %d. Too large\n", frame + 1, depth); return -EACCES; } continue_func: subprog_end = subprog[idx + 1].start; for (; i < subprog_end; i++) { if (insn[i].code != (BPF_JMP | BPF_CALL)) continue; if (insn[i].src_reg != BPF_PSEUDO_CALL) continue; /* remember insn and function to return to */ ret_insn[frame] = i + 1; ret_prog[frame] = idx; /* find the callee */ i = i + insn[i].imm + 1; idx = find_subprog(env, i); if (idx < 0) { WARN_ONCE(1, "verifier bug. No program starts at insn %d\n", i); return -EFAULT; } frame++; if (frame >= MAX_CALL_FRAMES) { WARN_ONCE(1, "verifier bug. Call stack is too deep\n"); return -EFAULT; } goto process_func; } /* end of for() loop means the last insn of the 'subprog' * was reached. Doesn't matter whether it was JA or EXIT */ if (frame == 0) return 0; depth -= round_up(max_t(u32, subprog[idx].stack_depth, 1), 32); frame--; i = ret_insn[frame]; idx = ret_prog[frame]; goto continue_func; } #ifndef CONFIG_BPF_JIT_ALWAYS_ON static int get_callee_stack_depth(struct bpf_verifier_env *env, const struct bpf_insn *insn, int idx) { int start = idx + insn->imm + 1, subprog; subprog = find_subprog(env, start); if (subprog < 0) { WARN_ONCE(1, "verifier bug. No program starts at insn %d\n", start); return -EFAULT; } return env->subprog_info[subprog].stack_depth; } #endif static int check_ctx_reg(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, int regno) { /* Access to ctx or passing it to a helper is only allowed in * its original, unmodified form. */ if (reg->off) { verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n", regno, reg->off); return -EACCES; } if (!tnum_is_const(reg->var_off) || reg->var_off.value) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf); return -EACCES; } return 0; } /* truncate register to smaller size (in bytes) * must be called with size < BPF_REG_SIZE */ static void coerce_reg_to_size(struct bpf_reg_state *reg, int size) { u64 mask; /* clear high bits in bit representation */ reg->var_off = tnum_cast(reg->var_off, size); /* fix arithmetic bounds */ mask = ((u64)1 << (size * 8)) - 1; if ((reg->umin_value & ~mask) == (reg->umax_value & ~mask)) { reg->umin_value &= mask; reg->umax_value &= mask; } else { reg->umin_value = 0; reg->umax_value = mask; } reg->smin_value = reg->umin_value; reg->smax_value = reg->umax_value; } /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory * if t==write && value_regno==-1, some unknown value is stored into memory * if t==read && value_regno==-1, don't care what we read from memory */ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno, int off, int bpf_size, enum bpf_access_type t, int value_regno, bool strict_alignment_once) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = regs + regno; struct bpf_func_state *state; int size, err = 0; size = bpf_size_to_bytes(bpf_size); if (size < 0) return size; /* alignment checks will add in reg->off themselves */ err = check_ptr_alignment(env, reg, off, size, strict_alignment_once); if (err) return err; /* for access checks, reg->off is just part of off */ off += reg->off; if (reg->type == PTR_TO_MAP_VALUE) { if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose(env, "R%d leaks addr into map\n", value_regno); return -EACCES; } err = check_map_access(env, regno, off, size, false); if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown(env, regs, value_regno); } else if (reg->type == PTR_TO_CTX) { enum bpf_reg_type reg_type = SCALAR_VALUE; if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose(env, "R%d leaks addr into ctx\n", value_regno); return -EACCES; } err = check_ctx_reg(env, reg, regno); if (err < 0) return err; err = check_ctx_access(env, insn_idx, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { /* ctx access returns either a scalar, or a * PTR_TO_PACKET[_META,_END]. In the latter * case, we know the offset is zero. */ if (reg_type == SCALAR_VALUE) mark_reg_unknown(env, regs, value_regno); else mark_reg_known_zero(env, regs, value_regno); regs[value_regno].id = 0; regs[value_regno].off = 0; regs[value_regno].range = 0; regs[value_regno].type = reg_type; } } else if (reg->type == PTR_TO_STACK) { /* stack accesses must be at a fixed offset, so that we can * determine what type of data were returned. * See check_stack_read(). */ if (!tnum_is_const(reg->var_off)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "variable stack access var_off=%s off=%d size=%d", tn_buf, off, size); return -EACCES; } off += reg->var_off.value; if (off >= 0 || off < -MAX_BPF_STACK) { verbose(env, "invalid stack off=%d size=%d\n", off, size); return -EACCES; } state = func(env, reg); err = update_stack_depth(env, state, off); if (err) return err; if (t == BPF_WRITE) err = check_stack_write(env, state, off, size, value_regno, insn_idx); else err = check_stack_read(env, state, off, size, value_regno); } else if (reg_is_pkt_pointer(reg)) { if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) { verbose(env, "cannot write into packet\n"); return -EACCES; } if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose(env, "R%d leaks addr into packet\n", value_regno); return -EACCES; } err = check_packet_access(env, regno, off, size, false); if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown(env, regs, value_regno); } else { verbose(env, "R%d invalid mem access '%s'\n", regno, reg_type_str[reg->type]); return -EACCES; } if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ && regs[value_regno].type == SCALAR_VALUE) { /* b/h/w load zero-extends, mark upper bits as known 0 */ coerce_reg_to_size(®s[value_regno], size); } return err; } static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn) { int err; if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) || insn->imm != 0) { verbose(env, "BPF_XADD uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; /* check src2 operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; if (is_pointer_value(env, insn->src_reg)) { verbose(env, "R%d leaks addr into mem\n", insn->src_reg); return -EACCES; } if (is_ctx_reg(env, insn->dst_reg) || is_pkt_reg(env, insn->dst_reg)) { verbose(env, "BPF_XADD stores into R%d %s is not allowed\n", insn->dst_reg, is_ctx_reg(env, insn->dst_reg) ? "context" : "packet"); return -EACCES; } /* check whether atomic_add can read the memory */ err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, -1, true); if (err) return err; /* check whether atomic_add can write into the same memory */ return check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1, true); } /* when register 'regno' is passed into function that will read 'access_size' * bytes from that pointer, make sure that it's within stack boundary * and all elements of stack are initialized. * Unlike most pointer bounds-checking functions, this one doesn't take an * 'off' argument, so it has to add in reg->off itself. */ static int check_stack_boundary(struct bpf_verifier_env *env, int regno, int access_size, bool zero_size_allowed, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *reg = cur_regs(env) + regno; struct bpf_func_state *state = func(env, reg); int off, i, slot, spi; if (reg->type != PTR_TO_STACK) { /* Allow zero-byte read from NULL, regardless of pointer type */ if (zero_size_allowed && access_size == 0 && register_is_null(reg)) return 0; verbose(env, "R%d type=%s expected=%s\n", regno, reg_type_str[reg->type], reg_type_str[PTR_TO_STACK]); return -EACCES; } /* Only allow fixed-offset stack reads */ if (!tnum_is_const(reg->var_off)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "invalid variable stack read R%d var_off=%s\n", regno, tn_buf); return -EACCES; } off = reg->off + reg->var_off.value; if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 || access_size < 0 || (access_size == 0 && !zero_size_allowed)) { verbose(env, "invalid stack type R%d off=%d access_size=%d\n", regno, off, access_size); return -EACCES; } if (meta && meta->raw_mode) { meta->access_size = access_size; meta->regno = regno; return 0; } for (i = 0; i < access_size; i++) { u8 *stype; slot = -(off + i) - 1; spi = slot / BPF_REG_SIZE; if (state->allocated_stack <= slot) goto err; stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; if (*stype == STACK_MISC) goto mark; if (*stype == STACK_ZERO) { /* helper can write anything into the stack */ *stype = STACK_MISC; goto mark; } err: verbose(env, "invalid indirect read from stack off %d+%d size %d\n", off, i, access_size); return -EACCES; mark: /* reading any byte out of 8-byte 'spill_slot' will cause * the whole slot to be marked as 'read' */ mark_stack_slot_read(env, env->cur_state, env->cur_state->parent, spi, state->frameno); } return update_stack_depth(env, state, off); } static int check_helper_mem_access(struct bpf_verifier_env *env, int regno, int access_size, bool zero_size_allowed, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; switch (reg->type) { case PTR_TO_PACKET: case PTR_TO_PACKET_META: return check_packet_access(env, regno, reg->off, access_size, zero_size_allowed); case PTR_TO_MAP_VALUE: return check_map_access(env, regno, reg->off, access_size, zero_size_allowed); default: /* scalar_value|ptr_to_stack or invalid ptr */ return check_stack_boundary(env, regno, access_size, zero_size_allowed, meta); } } static bool arg_type_is_mem_ptr(enum bpf_arg_type type) { return type == ARG_PTR_TO_MEM || type == ARG_PTR_TO_MEM_OR_NULL || type == ARG_PTR_TO_UNINIT_MEM; } static bool arg_type_is_mem_size(enum bpf_arg_type type) { return type == ARG_CONST_SIZE || type == ARG_CONST_SIZE_OR_ZERO; } static int check_func_arg(struct bpf_verifier_env *env, u32 regno, enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; enum bpf_reg_type expected_type, type = reg->type; int err = 0; if (arg_type == ARG_DONTCARE) return 0; err = check_reg_arg(env, regno, SRC_OP); if (err) return err; if (arg_type == ARG_ANYTHING) { if (is_pointer_value(env, regno)) { verbose(env, "R%d leaks addr into helper function\n", regno); return -EACCES; } return 0; } if (type_is_pkt_pointer(type) && !may_access_direct_pkt_data(env, meta, BPF_READ)) { verbose(env, "helper access to the packet is not allowed\n"); return -EACCES; } if (arg_type == ARG_PTR_TO_MAP_KEY || arg_type == ARG_PTR_TO_MAP_VALUE) { expected_type = PTR_TO_STACK; if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE && type != expected_type) goto err_type; } else if (arg_type == ARG_CONST_SIZE || arg_type == ARG_CONST_SIZE_OR_ZERO) { expected_type = SCALAR_VALUE; if (type != expected_type) goto err_type; } else if (arg_type == ARG_CONST_MAP_PTR) { expected_type = CONST_PTR_TO_MAP; if (type != expected_type) goto err_type; } else if (arg_type == ARG_PTR_TO_CTX) { expected_type = PTR_TO_CTX; if (type != expected_type) goto err_type; err = check_ctx_reg(env, reg, regno); if (err < 0) return err; } else if (arg_type_is_mem_ptr(arg_type)) { expected_type = PTR_TO_STACK; /* One exception here. In case function allows for NULL to be * passed in as argument, it's a SCALAR_VALUE type. Final test * happens during stack boundary checking. */ if (register_is_null(reg) && arg_type == ARG_PTR_TO_MEM_OR_NULL) /* final test in check_stack_boundary() */; else if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE && type != expected_type) goto err_type; meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM; } else { verbose(env, "unsupported arg_type %d\n", arg_type); return -EFAULT; } if (arg_type == ARG_CONST_MAP_PTR) { /* bpf_map_xxx(map_ptr) call: remember that map_ptr */ meta->map_ptr = reg->map_ptr; } else if (arg_type == ARG_PTR_TO_MAP_KEY) { /* bpf_map_xxx(..., map_ptr, ..., key) call: * check that [key, key + map->key_size) are within * stack limits and initialized */ if (!meta->map_ptr) { /* in function declaration map_ptr must come before * map_key, so that it's verified and known before * we have to check map_key here. Otherwise it means * that kernel subsystem misconfigured verifier */ verbose(env, "invalid map_ptr to access map->key\n"); return -EACCES; } err = check_helper_mem_access(env, regno, meta->map_ptr->key_size, false, NULL); } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { /* bpf_map_xxx(..., map_ptr, ..., value) call: * check [value, value + map->value_size) validity */ if (!meta->map_ptr) { /* kernel subsystem misconfigured verifier */ verbose(env, "invalid map_ptr to access map->value\n"); return -EACCES; } err = check_helper_mem_access(env, regno, meta->map_ptr->value_size, false, NULL); } else if (arg_type_is_mem_size(arg_type)) { bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO); /* remember the mem_size which may be used later * to refine return values. */ meta->msize_smax_value = reg->smax_value; meta->msize_umax_value = reg->umax_value; /* The register is SCALAR_VALUE; the access check * happens using its boundaries. */ if (!tnum_is_const(reg->var_off)) /* For unprivileged variable accesses, disable raw * mode so that the program is required to * initialize all the memory that the helper could * just partially fill up. */ meta = NULL; if (reg->smin_value < 0) { verbose(env, "R%d min value is negative, either use unsigned or 'var &= const'\n", regno); return -EACCES; } if (reg->umin_value == 0) { err = check_helper_mem_access(env, regno - 1, 0, zero_size_allowed, meta); if (err) return err; } if (reg->umax_value >= BPF_MAX_VAR_SIZ) { verbose(env, "R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n", regno); return -EACCES; } err = check_helper_mem_access(env, regno - 1, reg->umax_value, zero_size_allowed, meta); } return err; err_type: verbose(env, "R%d type=%s expected=%s\n", regno, reg_type_str[type], reg_type_str[expected_type]); return -EACCES; } static int check_map_func_compatibility(struct bpf_verifier_env *env, struct bpf_map *map, int func_id) { if (!map) return 0; /* We need a two way check, first is from map perspective ... */ switch (map->map_type) { case BPF_MAP_TYPE_PROG_ARRAY: if (func_id != BPF_FUNC_tail_call) goto error; break; case BPF_MAP_TYPE_PERF_EVENT_ARRAY: if (func_id != BPF_FUNC_perf_event_read && func_id != BPF_FUNC_perf_event_output && func_id != BPF_FUNC_perf_event_read_value) goto error; break; case BPF_MAP_TYPE_STACK_TRACE: if (func_id != BPF_FUNC_get_stackid) goto error; break; case BPF_MAP_TYPE_CGROUP_ARRAY: if (func_id != BPF_FUNC_skb_under_cgroup && func_id != BPF_FUNC_current_task_under_cgroup) goto error; break; case BPF_MAP_TYPE_CGROUP_STORAGE: if (func_id != BPF_FUNC_get_local_storage) goto error; break; /* devmap returns a pointer to a live net_device ifindex that we cannot * allow to be modified from bpf side. So do not allow lookup elements * for now. */ case BPF_MAP_TYPE_DEVMAP: if (func_id != BPF_FUNC_redirect_map) goto error; break; /* Restrict bpf side of cpumap and xskmap, open when use-cases * appear. */ case BPF_MAP_TYPE_CPUMAP: case BPF_MAP_TYPE_XSKMAP: if (func_id != BPF_FUNC_redirect_map) goto error; break; case BPF_MAP_TYPE_ARRAY_OF_MAPS: case BPF_MAP_TYPE_HASH_OF_MAPS: if (func_id != BPF_FUNC_map_lookup_elem) goto error; break; case BPF_MAP_TYPE_SOCKMAP: if (func_id != BPF_FUNC_sk_redirect_map && func_id != BPF_FUNC_sock_map_update && func_id != BPF_FUNC_map_delete_elem && func_id != BPF_FUNC_msg_redirect_map) goto error; break; case BPF_MAP_TYPE_SOCKHASH: if (func_id != BPF_FUNC_sk_redirect_hash && func_id != BPF_FUNC_sock_hash_update && func_id != BPF_FUNC_map_delete_elem && func_id != BPF_FUNC_msg_redirect_hash) goto error; break; case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY: if (func_id != BPF_FUNC_sk_select_reuseport) goto error; break; default: break; } /* ... and second from the function itself. */ switch (func_id) { case BPF_FUNC_tail_call: if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY) goto error; if (env->subprog_cnt > 1) { verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n"); return -EINVAL; } break; case BPF_FUNC_perf_event_read: case BPF_FUNC_perf_event_output: case BPF_FUNC_perf_event_read_value: if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) goto error; break; case BPF_FUNC_get_stackid: if (map->map_type != BPF_MAP_TYPE_STACK_TRACE) goto error; break; case BPF_FUNC_current_task_under_cgroup: case BPF_FUNC_skb_under_cgroup: if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY) goto error; break; case BPF_FUNC_redirect_map: if (map->map_type != BPF_MAP_TYPE_DEVMAP && map->map_type != BPF_MAP_TYPE_CPUMAP && map->map_type != BPF_MAP_TYPE_XSKMAP) goto error; break; case BPF_FUNC_sk_redirect_map: case BPF_FUNC_msg_redirect_map: case BPF_FUNC_sock_map_update: if (map->map_type != BPF_MAP_TYPE_SOCKMAP) goto error; break; case BPF_FUNC_sk_redirect_hash: case BPF_FUNC_msg_redirect_hash: case BPF_FUNC_sock_hash_update: if (map->map_type != BPF_MAP_TYPE_SOCKHASH) goto error; break; case BPF_FUNC_get_local_storage: if (map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE) goto error; break; case BPF_FUNC_sk_select_reuseport: if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) goto error; break; default: break; } return 0; error: verbose(env, "cannot pass map_type %d into func %s#%d\n", map->map_type, func_id_name(func_id), func_id); return -EINVAL; } static bool check_raw_mode_ok(const struct bpf_func_proto *fn) { int count = 0; if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM) count++; if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM) count++; /* We only support one arg being in raw mode at the moment, * which is sufficient for the helper functions we have * right now. */ return count <= 1; } static bool check_args_pair_invalid(enum bpf_arg_type arg_curr, enum bpf_arg_type arg_next) { return (arg_type_is_mem_ptr(arg_curr) && !arg_type_is_mem_size(arg_next)) || (!arg_type_is_mem_ptr(arg_curr) && arg_type_is_mem_size(arg_next)); } static bool check_arg_pair_ok(const struct bpf_func_proto *fn) { /* bpf_xxx(..., buf, len) call will access 'len' * bytes from memory 'buf'. Both arg types need * to be paired, so make sure there's no buggy * helper function specification. */ if (arg_type_is_mem_size(fn->arg1_type) || arg_type_is_mem_ptr(fn->arg5_type) || check_args_pair_invalid(fn->arg1_type, fn->arg2_type) || check_args_pair_invalid(fn->arg2_type, fn->arg3_type) || check_args_pair_invalid(fn->arg3_type, fn->arg4_type) || check_args_pair_invalid(fn->arg4_type, fn->arg5_type)) return false; return true; } static int check_func_proto(const struct bpf_func_proto *fn) { return check_raw_mode_ok(fn) && check_arg_pair_ok(fn) ? 0 : -EINVAL; } /* Packet data might have moved, any old PTR_TO_PACKET[_META,_END] * are now invalid, so turn them into unknown SCALAR_VALUE. */ static void __clear_all_pkt_pointers(struct bpf_verifier_env *env, struct bpf_func_state *state) { struct bpf_reg_state *regs = state->regs, *reg; int i; for (i = 0; i < MAX_BPF_REG; i++) if (reg_is_pkt_pointer_any(®s[i])) mark_reg_unknown(env, regs, i); for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) { if (state->stack[i].slot_type[0] != STACK_SPILL) continue; reg = &state->stack[i].spilled_ptr; if (reg_is_pkt_pointer_any(reg)) __mark_reg_unknown(reg); } } static void clear_all_pkt_pointers(struct bpf_verifier_env *env) { struct bpf_verifier_state *vstate = env->cur_state; int i; for (i = 0; i <= vstate->curframe; i++) __clear_all_pkt_pointers(env, vstate->frame[i]); } static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn, int *insn_idx) { struct bpf_verifier_state *state = env->cur_state; struct bpf_func_state *caller, *callee; int i, subprog, target_insn; if (state->curframe + 1 >= MAX_CALL_FRAMES) { verbose(env, "the call stack of %d frames is too deep\n", state->curframe + 2); return -E2BIG; } target_insn = *insn_idx + insn->imm; subprog = find_subprog(env, target_insn + 1); if (subprog < 0) { verbose(env, "verifier bug. No program starts at insn %d\n", target_insn + 1); return -EFAULT; } caller = state->frame[state->curframe]; if (state->frame[state->curframe + 1]) { verbose(env, "verifier bug. Frame %d already allocated\n", state->curframe + 1); return -EFAULT; } callee = kzalloc(sizeof(*callee), GFP_KERNEL); if (!callee) return -ENOMEM; state->frame[state->curframe + 1] = callee; /* callee cannot access r0, r6 - r9 for reading and has to write * into its own stack before reading from it. * callee can read/write into caller's stack */ init_func_state(env, callee, /* remember the callsite, it will be used by bpf_exit */ *insn_idx /* callsite */, state->curframe + 1 /* frameno within this callchain */, subprog /* subprog number within this prog */); /* copy r1 - r5 args that callee can access */ for (i = BPF_REG_1; i <= BPF_REG_5; i++) callee->regs[i] = caller->regs[i]; /* after the call regsiters r0 - r5 were scratched */ for (i = 0; i < CALLER_SAVED_REGS; i++) { mark_reg_not_init(env, caller->regs, caller_saved[i]); check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK); } /* only increment it after check_reg_arg() finished */ state->curframe++; /* and go analyze first insn of the callee */ *insn_idx = target_insn; if (env->log.level) { verbose(env, "caller:\n"); print_verifier_state(env, caller); verbose(env, "callee:\n"); print_verifier_state(env, callee); } return 0; } static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) { struct bpf_verifier_state *state = env->cur_state; struct bpf_func_state *caller, *callee; struct bpf_reg_state *r0; callee = state->frame[state->curframe]; r0 = &callee->regs[BPF_REG_0]; if (r0->type == PTR_TO_STACK) { /* technically it's ok to return caller's stack pointer * (or caller's caller's pointer) back to the caller, * since these pointers are valid. Only current stack * pointer will be invalid as soon as function exits, * but let's be conservative */ verbose(env, "cannot return stack pointer to the caller\n"); return -EINVAL; } state->curframe--; caller = state->frame[state->curframe]; /* return to the caller whatever r0 had in the callee */ caller->regs[BPF_REG_0] = *r0; *insn_idx = callee->callsite + 1; if (env->log.level) { verbose(env, "returning from callee:\n"); print_verifier_state(env, callee); verbose(env, "to caller at %d:\n", *insn_idx); print_verifier_state(env, caller); } /* clear everything in the callee */ free_func_state(callee); state->frame[state->curframe + 1] = NULL; return 0; } static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type, int func_id, struct bpf_call_arg_meta *meta) { struct bpf_reg_state *ret_reg = ®s[BPF_REG_0]; if (ret_type != RET_INTEGER || (func_id != BPF_FUNC_get_stack && func_id != BPF_FUNC_probe_read_str)) return; ret_reg->smax_value = meta->msize_smax_value; ret_reg->umax_value = meta->msize_umax_value; __reg_deduce_bounds(ret_reg); __reg_bound_offset(ret_reg); } static int record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta, int func_id, int insn_idx) { struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx]; if (func_id != BPF_FUNC_tail_call && func_id != BPF_FUNC_map_lookup_elem && func_id != BPF_FUNC_map_update_elem && func_id != BPF_FUNC_map_delete_elem) return 0; if (meta->map_ptr == NULL) { verbose(env, "kernel subsystem misconfigured verifier\n"); return -EINVAL; } if (!BPF_MAP_PTR(aux->map_state)) bpf_map_ptr_store(aux, meta->map_ptr, meta->map_ptr->unpriv_array); else if (BPF_MAP_PTR(aux->map_state) != meta->map_ptr) bpf_map_ptr_store(aux, BPF_MAP_PTR_POISON, meta->map_ptr->unpriv_array); return 0; } static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn_idx) { const struct bpf_func_proto *fn = NULL; struct bpf_reg_state *regs; struct bpf_call_arg_meta meta; bool changes_data; int i, err; /* find function prototype */ if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) { verbose(env, "invalid func %s#%d\n", func_id_name(func_id), func_id); return -EINVAL; } if (env->ops->get_func_proto) fn = env->ops->get_func_proto(func_id, env->prog); if (!fn) { verbose(env, "unknown func %s#%d\n", func_id_name(func_id), func_id); return -EINVAL; } /* eBPF programs must be GPL compatible to use GPL-ed functions */ if (!env->prog->gpl_compatible && fn->gpl_only) { verbose(env, "cannot call GPL-restricted function from non-GPL compatible program\n"); return -EINVAL; } /* With LD_ABS/IND some JITs save/restore skb from r1. */ changes_data = bpf_helper_changes_pkt_data(fn->func); if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) { verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n", func_id_name(func_id), func_id); return -EINVAL; } memset(&meta, 0, sizeof(meta)); meta.pkt_access = fn->pkt_access; err = check_func_proto(fn); if (err) { verbose(env, "kernel subsystem misconfigured func %s#%d\n", func_id_name(func_id), func_id); return err; } /* check args */ err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta); if (err) return err; err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta); if (err) return err; err = record_func_map(env, &meta, func_id, insn_idx); if (err) return err; /* Mark slots with STACK_MISC in case of raw mode, stack offset * is inferred from register state. */ for (i = 0; i < meta.access_size; i++) { err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1, false); if (err) return err; } regs = cur_regs(env); /* check that flags argument in get_local_storage(map, flags) is 0, * this is required because get_local_storage() can't return an error. */ if (func_id == BPF_FUNC_get_local_storage && !register_is_null(®s[BPF_REG_2])) { verbose(env, "get_local_storage() doesn't support non-zero flags\n"); return -EINVAL; } /* reset caller saved regs */ for (i = 0; i < CALLER_SAVED_REGS; i++) { mark_reg_not_init(env, regs, caller_saved[i]); check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK); } /* update return register (already marked as written above) */ if (fn->ret_type == RET_INTEGER) { /* sets type to SCALAR_VALUE */ mark_reg_unknown(env, regs, BPF_REG_0); } else if (fn->ret_type == RET_VOID) { regs[BPF_REG_0].type = NOT_INIT; } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL || fn->ret_type == RET_PTR_TO_MAP_VALUE) { if (fn->ret_type == RET_PTR_TO_MAP_VALUE) regs[BPF_REG_0].type = PTR_TO_MAP_VALUE; else regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL; /* There is no offset yet applied, variable or fixed */ mark_reg_known_zero(env, regs, BPF_REG_0); regs[BPF_REG_0].off = 0; /* remember map_ptr, so that check_map_access() * can check 'value_size' boundary of memory access * to map element returned from bpf_map_lookup_elem() */ if (meta.map_ptr == NULL) { verbose(env, "kernel subsystem misconfigured verifier\n"); return -EINVAL; } regs[BPF_REG_0].map_ptr = meta.map_ptr; regs[BPF_REG_0].id = ++env->id_gen; } else { verbose(env, "unknown return type %d of func %s#%d\n", fn->ret_type, func_id_name(func_id), func_id); return -EINVAL; } do_refine_retval_range(regs, fn->ret_type, func_id, &meta); err = check_map_func_compatibility(env, meta.map_ptr, func_id); if (err) return err; if (func_id == BPF_FUNC_get_stack && !env->prog->has_callchain_buf) { const char *err_str; #ifdef CONFIG_PERF_EVENTS err = get_callchain_buffers(sysctl_perf_event_max_stack); err_str = "cannot get callchain buffer for func %s#%d\n"; #else err = -ENOTSUPP; err_str = "func %s#%d not supported without CONFIG_PERF_EVENTS\n"; #endif if (err) { verbose(env, err_str, func_id_name(func_id), func_id); return err; } env->prog->has_callchain_buf = true; } if (changes_data) clear_all_pkt_pointers(env); return 0; } static bool signed_add_overflows(s64 a, s64 b) { /* Do the add in u64, where overflow is well-defined */ s64 res = (s64)((u64)a + (u64)b); if (b < 0) return res > a; return res < a; } static bool signed_sub_overflows(s64 a, s64 b) { /* Do the sub in u64, where overflow is well-defined */ s64 res = (s64)((u64)a - (u64)b); if (b < 0) return res < a; return res > a; } static bool check_reg_sane_offset(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, enum bpf_reg_type type) { bool known = tnum_is_const(reg->var_off); s64 val = reg->var_off.value; s64 smin = reg->smin_value; if (known && (val >= BPF_MAX_VAR_OFF || val <= -BPF_MAX_VAR_OFF)) { verbose(env, "math between %s pointer and %lld is not allowed\n", reg_type_str[type], val); return false; } if (reg->off >= BPF_MAX_VAR_OFF || reg->off <= -BPF_MAX_VAR_OFF) { verbose(env, "%s pointer offset %d is not allowed\n", reg_type_str[type], reg->off); return false; } if (smin == S64_MIN) { verbose(env, "math between %s pointer and register with unbounded min value is not allowed\n", reg_type_str[type]); return false; } if (smin >= BPF_MAX_VAR_OFF || smin <= -BPF_MAX_VAR_OFF) { verbose(env, "value %lld makes %s pointer be out of bounds\n", smin, reg_type_str[type]); return false; } return true; } /* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off. * Caller should also handle BPF_MOV case separately. * If we return -EACCES, caller may want to try again treating pointer as a * scalar. So we only emit a diagnostic if !env->allow_ptr_leaks. */ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, struct bpf_insn *insn, const struct bpf_reg_state *ptr_reg, const struct bpf_reg_state *off_reg) { struct bpf_verifier_state *vstate = env->cur_state; struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *regs = state->regs, *dst_reg; bool known = tnum_is_const(off_reg->var_off); s64 smin_val = off_reg->smin_value, smax_val = off_reg->smax_value, smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value; u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value, umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value; u8 opcode = BPF_OP(insn->code); u32 dst = insn->dst_reg; dst_reg = ®s[dst]; if ((known && (smin_val != smax_val || umin_val != umax_val)) || smin_val > smax_val || umin_val > umax_val) { /* Taint dst register if offset had invalid bounds derived from * e.g. dead branches. */ __mark_reg_unknown(dst_reg); return 0; } if (BPF_CLASS(insn->code) != BPF_ALU64) { /* 32-bit ALU ops on pointers produce (meaningless) scalars */ verbose(env, "R%d 32-bit pointer arithmetic prohibited\n", dst); return -EACCES; } if (ptr_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { verbose(env, "R%d pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL prohibited, null-check it first\n", dst); return -EACCES; } if (ptr_reg->type == CONST_PTR_TO_MAP) { verbose(env, "R%d pointer arithmetic on CONST_PTR_TO_MAP prohibited\n", dst); return -EACCES; } if (ptr_reg->type == PTR_TO_PACKET_END) { verbose(env, "R%d pointer arithmetic on PTR_TO_PACKET_END prohibited\n", dst); return -EACCES; } /* In case of 'scalar += pointer', dst_reg inherits pointer type and id. * The id may be overwritten later if we create a new variable offset. */ dst_reg->type = ptr_reg->type; dst_reg->id = ptr_reg->id; if (!check_reg_sane_offset(env, off_reg, ptr_reg->type) || !check_reg_sane_offset(env, ptr_reg, ptr_reg->type)) return -EINVAL; switch (opcode) { case BPF_ADD: /* We can take a fixed offset as long as it doesn't overflow * the s32 'off' field */ if (known && (ptr_reg->off + smin_val == (s64)(s32)(ptr_reg->off + smin_val))) { /* pointer += K. Accumulate it into fixed offset */ dst_reg->smin_value = smin_ptr; dst_reg->smax_value = smax_ptr; dst_reg->umin_value = umin_ptr; dst_reg->umax_value = umax_ptr; dst_reg->var_off = ptr_reg->var_off; dst_reg->off = ptr_reg->off + smin_val; dst_reg->range = ptr_reg->range; break; } /* A new variable offset is created. Note that off_reg->off * == 0, since it's a scalar. * dst_reg gets the pointer type and since some positive * integer value was added to the pointer, give it a new 'id' * if it's a PTR_TO_PACKET. * this creates a new 'base' pointer, off_reg (variable) gets * added into the variable offset, and we copy the fixed offset * from ptr_reg. */ if (signed_add_overflows(smin_ptr, smin_val) || signed_add_overflows(smax_ptr, smax_val)) { dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { dst_reg->smin_value = smin_ptr + smin_val; dst_reg->smax_value = smax_ptr + smax_val; } if (umin_ptr + umin_val < umin_ptr || umax_ptr + umax_val < umax_ptr) { dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; } else { dst_reg->umin_value = umin_ptr + umin_val; dst_reg->umax_value = umax_ptr + umax_val; } dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off); dst_reg->off = ptr_reg->off; if (reg_is_pkt_pointer(ptr_reg)) { dst_reg->id = ++env->id_gen; /* something was added to pkt_ptr, set range to zero */ dst_reg->range = 0; } break; case BPF_SUB: if (dst_reg == off_reg) { /* scalar -= pointer. Creates an unknown scalar */ verbose(env, "R%d tried to subtract pointer from scalar\n", dst); return -EACCES; } /* We don't allow subtraction from FP, because (according to * test_verifier.c test "invalid fp arithmetic", JITs might not * be able to deal with it. */ if (ptr_reg->type == PTR_TO_STACK) { verbose(env, "R%d subtraction from stack pointer prohibited\n", dst); return -EACCES; } if (known && (ptr_reg->off - smin_val == (s64)(s32)(ptr_reg->off - smin_val))) { /* pointer -= K. Subtract it from fixed offset */ dst_reg->smin_value = smin_ptr; dst_reg->smax_value = smax_ptr; dst_reg->umin_value = umin_ptr; dst_reg->umax_value = umax_ptr; dst_reg->var_off = ptr_reg->var_off; dst_reg->id = ptr_reg->id; dst_reg->off = ptr_reg->off - smin_val; dst_reg->range = ptr_reg->range; break; } /* A new variable offset is created. If the subtrahend is known * nonnegative, then any reg->range we had before is still good. */ if (signed_sub_overflows(smin_ptr, smax_val) || signed_sub_overflows(smax_ptr, smin_val)) { /* Overflow possible, we know nothing */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { dst_reg->smin_value = smin_ptr - smax_val; dst_reg->smax_value = smax_ptr - smin_val; } if (umin_ptr < umax_val) { /* Overflow possible, we know nothing */ dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; } else { /* Cannot overflow (as long as bounds are consistent) */ dst_reg->umin_value = umin_ptr - umax_val; dst_reg->umax_value = umax_ptr - umin_val; } dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off); dst_reg->off = ptr_reg->off; if (reg_is_pkt_pointer(ptr_reg)) { dst_reg->id = ++env->id_gen; /* something was added to pkt_ptr, set range to zero */ if (smin_val < 0) dst_reg->range = 0; } break; case BPF_AND: case BPF_OR: case BPF_XOR: /* bitwise ops on pointers are troublesome, prohibit. */ verbose(env, "R%d bitwise operator %s on pointer prohibited\n", dst, bpf_alu_string[opcode >> 4]); return -EACCES; default: /* other operators (e.g. MUL,LSH) produce non-pointer results */ verbose(env, "R%d pointer arithmetic with %s operator prohibited\n", dst, bpf_alu_string[opcode >> 4]); return -EACCES; } if (!check_reg_sane_offset(env, dst_reg, ptr_reg->type)) return -EINVAL; __update_reg_bounds(dst_reg); __reg_deduce_bounds(dst_reg); __reg_bound_offset(dst_reg); return 0; } /* WARNING: This function does calculations on 64-bit values, but the actual * execution may occur on 32-bit values. Therefore, things like bitshifts * need extra checks in the 32-bit case. */ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env, struct bpf_insn *insn, struct bpf_reg_state *dst_reg, struct bpf_reg_state src_reg) { struct bpf_reg_state *regs = cur_regs(env); u8 opcode = BPF_OP(insn->code); bool src_known, dst_known; s64 smin_val, smax_val; u64 umin_val, umax_val; u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32; if (insn_bitness == 32) { /* Relevant for 32-bit RSH: Information can propagate towards * LSB, so it isn't sufficient to only truncate the output to * 32 bits. */ coerce_reg_to_size(dst_reg, 4); coerce_reg_to_size(&src_reg, 4); } smin_val = src_reg.smin_value; smax_val = src_reg.smax_value; umin_val = src_reg.umin_value; umax_val = src_reg.umax_value; src_known = tnum_is_const(src_reg.var_off); dst_known = tnum_is_const(dst_reg->var_off); if ((src_known && (smin_val != smax_val || umin_val != umax_val)) || smin_val > smax_val || umin_val > umax_val) { /* Taint dst register if offset had invalid bounds derived from * e.g. dead branches. */ __mark_reg_unknown(dst_reg); return 0; } if (!src_known && opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) { __mark_reg_unknown(dst_reg); return 0; } switch (opcode) { case BPF_ADD: if (signed_add_overflows(dst_reg->smin_value, smin_val) || signed_add_overflows(dst_reg->smax_value, smax_val)) { dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { dst_reg->smin_value += smin_val; dst_reg->smax_value += smax_val; } if (dst_reg->umin_value + umin_val < umin_val || dst_reg->umax_value + umax_val < umax_val) { dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; } else { dst_reg->umin_value += umin_val; dst_reg->umax_value += umax_val; } dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off); break; case BPF_SUB: if (signed_sub_overflows(dst_reg->smin_value, smax_val) || signed_sub_overflows(dst_reg->smax_value, smin_val)) { /* Overflow possible, we know nothing */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { dst_reg->smin_value -= smax_val; dst_reg->smax_value -= smin_val; } if (dst_reg->umin_value < umax_val) { /* Overflow possible, we know nothing */ dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; } else { /* Cannot overflow (as long as bounds are consistent) */ dst_reg->umin_value -= umax_val; dst_reg->umax_value -= umin_val; } dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off); break; case BPF_MUL: dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off); if (smin_val < 0 || dst_reg->smin_value < 0) { /* Ain't nobody got time to multiply that sign */ __mark_reg_unbounded(dst_reg); __update_reg_bounds(dst_reg); break; } /* Both values are positive, so we can work with unsigned and * copy the result to signed (unless it exceeds S64_MAX). */ if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) { /* Potential overflow, we know nothing */ __mark_reg_unbounded(dst_reg); /* (except what we can learn from the var_off) */ __update_reg_bounds(dst_reg); break; } dst_reg->umin_value *= umin_val; dst_reg->umax_value *= umax_val; if (dst_reg->umax_value > S64_MAX) { /* Overflow possible, we know nothing */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { dst_reg->smin_value = dst_reg->umin_value; dst_reg->smax_value = dst_reg->umax_value; } break; case BPF_AND: if (src_known && dst_known) { __mark_reg_known(dst_reg, dst_reg->var_off.value & src_reg.var_off.value); break; } /* We get our minimum from the var_off, since that's inherently * bitwise. Our maximum is the minimum of the operands' maxima. */ dst_reg->var_off = tnum_and(dst_reg->var_off, src_reg.var_off); dst_reg->umin_value = dst_reg->var_off.value; dst_reg->umax_value = min(dst_reg->umax_value, umax_val); if (dst_reg->smin_value < 0 || smin_val < 0) { /* Lose signed bounds when ANDing negative numbers, * ain't nobody got time for that. */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { /* ANDing two positives gives a positive, so safe to * cast result into s64. */ dst_reg->smin_value = dst_reg->umin_value; dst_reg->smax_value = dst_reg->umax_value; } /* We may learn something more from the var_off */ __update_reg_bounds(dst_reg); break; case BPF_OR: if (src_known && dst_known) { __mark_reg_known(dst_reg, dst_reg->var_off.value | src_reg.var_off.value); break; } /* We get our maximum from the var_off, and our minimum is the * maximum of the operands' minima */ dst_reg->var_off = tnum_or(dst_reg->var_off, src_reg.var_off); dst_reg->umin_value = max(dst_reg->umin_value, umin_val); dst_reg->umax_value = dst_reg->var_off.value | dst_reg->var_off.mask; if (dst_reg->smin_value < 0 || smin_val < 0) { /* Lose signed bounds when ORing negative numbers, * ain't nobody got time for that. */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; } else { /* ORing two positives gives a positive, so safe to * cast result into s64. */ dst_reg->smin_value = dst_reg->umin_value; dst_reg->smax_value = dst_reg->umax_value; } /* We may learn something more from the var_off */ __update_reg_bounds(dst_reg); break; case BPF_LSH: if (umax_val >= insn_bitness) { /* Shifts greater than 31 or 63 are undefined. * This includes shifts by a negative number. */ mark_reg_unknown(env, regs, insn->dst_reg); break; } /* We lose all sign bit information (except what we can pick * up from var_off) */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; /* If we might shift our top bit out, then we know nothing */ if (dst_reg->umax_value > 1ULL << (63 - umax_val)) { dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; } else { dst_reg->umin_value <<= umin_val; dst_reg->umax_value <<= umax_val; } dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val); /* We may learn something more from the var_off */ __update_reg_bounds(dst_reg); break; case BPF_RSH: if (umax_val >= insn_bitness) { /* Shifts greater than 31 or 63 are undefined. * This includes shifts by a negative number. */ mark_reg_unknown(env, regs, insn->dst_reg); break; } /* BPF_RSH is an unsigned shift. If the value in dst_reg might * be negative, then either: * 1) src_reg might be zero, so the sign bit of the result is * unknown, so we lose our signed bounds * 2) it's known negative, thus the unsigned bounds capture the * signed bounds * 3) the signed bounds cross zero, so they tell us nothing * about the result * If the value in dst_reg is known nonnegative, then again the * unsigned bounts capture the signed bounds. * Thus, in all cases it suffices to blow away our signed bounds * and rely on inferring new ones from the unsigned bounds and * var_off of the result. */ dst_reg->smin_value = S64_MIN; dst_reg->smax_value = S64_MAX; dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val); dst_reg->umin_value >>= umax_val; dst_reg->umax_value >>= umin_val; /* We may learn something more from the var_off */ __update_reg_bounds(dst_reg); break; case BPF_ARSH: if (umax_val >= insn_bitness) { /* Shifts greater than 31 or 63 are undefined. * This includes shifts by a negative number. */ mark_reg_unknown(env, regs, insn->dst_reg); break; } /* Upon reaching here, src_known is true and * umax_val is equal to umin_val. */ dst_reg->smin_value >>= umin_val; dst_reg->smax_value >>= umin_val; dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val); /* blow away the dst_reg umin_value/umax_value and rely on * dst_reg var_off to refine the result. */ dst_reg->umin_value = 0; dst_reg->umax_value = U64_MAX; __update_reg_bounds(dst_reg); break; default: mark_reg_unknown(env, regs, insn->dst_reg); break; } if (BPF_CLASS(insn->code) != BPF_ALU64) { /* 32-bit ALU ops are (32,32)->32 */ coerce_reg_to_size(dst_reg, 4); } __reg_deduce_bounds(dst_reg); __reg_bound_offset(dst_reg); return 0; } /* Handles ALU ops other than BPF_END, BPF_NEG and BPF_MOV: computes new min/max * and var_off. */ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_verifier_state *vstate = env->cur_state; struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *regs = state->regs, *dst_reg, *src_reg; struct bpf_reg_state *ptr_reg = NULL, off_reg = {0}; u8 opcode = BPF_OP(insn->code); dst_reg = ®s[insn->dst_reg]; src_reg = NULL; if (dst_reg->type != SCALAR_VALUE) ptr_reg = dst_reg; if (BPF_SRC(insn->code) == BPF_X) { src_reg = ®s[insn->src_reg]; if (src_reg->type != SCALAR_VALUE) { if (dst_reg->type != SCALAR_VALUE) { /* Combining two pointers by any ALU op yields * an arbitrary scalar. Disallow all math except * pointer subtraction */ if (opcode == BPF_SUB && env->allow_ptr_leaks) { mark_reg_unknown(env, regs, insn->dst_reg); return 0; } verbose(env, "R%d pointer %s pointer prohibited\n", insn->dst_reg, bpf_alu_string[opcode >> 4]); return -EACCES; } else { /* scalar += pointer * This is legal, but we have to reverse our * src/dest handling in computing the range */ return adjust_ptr_min_max_vals(env, insn, src_reg, dst_reg); } } else if (ptr_reg) { /* pointer += scalar */ return adjust_ptr_min_max_vals(env, insn, dst_reg, src_reg); } } else { /* Pretend the src is a reg with a known value, since we only * need to be able to read from this state. */ off_reg.type = SCALAR_VALUE; __mark_reg_known(&off_reg, insn->imm); src_reg = &off_reg; if (ptr_reg) /* pointer += K */ return adjust_ptr_min_max_vals(env, insn, ptr_reg, src_reg); } /* Got here implies adding two SCALAR_VALUEs */ if (WARN_ON_ONCE(ptr_reg)) { print_verifier_state(env, state); verbose(env, "verifier internal error: unexpected ptr_reg\n"); return -EINVAL; } if (WARN_ON(!src_reg)) { print_verifier_state(env, state); verbose(env, "verifier internal error: no src_reg\n"); return -EINVAL; } return adjust_scalar_min_max_vals(env, insn, dst_reg, *src_reg); } /* check validity of 32-bit and 64-bit arithmetic operations */ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = cur_regs(env); u8 opcode = BPF_OP(insn->code); int err; if (opcode == BPF_END || opcode == BPF_NEG) { if (opcode == BPF_NEG) { if (BPF_SRC(insn->code) != 0 || insn->src_reg != BPF_REG_0 || insn->off != 0 || insn->imm != 0) { verbose(env, "BPF_NEG uses reserved fields\n"); return -EINVAL; } } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0 || (insn->imm != 16 && insn->imm != 32 && insn->imm != 64) || BPF_CLASS(insn->code) == BPF_ALU64) { verbose(env, "BPF_END uses reserved fields\n"); return -EINVAL; } } /* check src operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; if (is_pointer_value(env, insn->dst_reg)) { verbose(env, "R%d pointer arithmetic prohibited\n", insn->dst_reg); return -EACCES; } /* check dest operand */ err = check_reg_arg(env, insn->dst_reg, DST_OP); if (err) return err; } else if (opcode == BPF_MOV) { if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0 || insn->off != 0) { verbose(env, "BPF_MOV uses reserved fields\n"); return -EINVAL; } /* check src operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0) { verbose(env, "BPF_MOV uses reserved fields\n"); return -EINVAL; } } /* check dest operand, mark as required later */ err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK); if (err) return err; if (BPF_SRC(insn->code) == BPF_X) { if (BPF_CLASS(insn->code) == BPF_ALU64) { /* case: R1 = R2 * copy register state to dest reg */ regs[insn->dst_reg] = regs[insn->src_reg]; regs[insn->dst_reg].live |= REG_LIVE_WRITTEN; } else { /* R1 = (u32) R2 */ if (is_pointer_value(env, insn->src_reg)) { verbose(env, "R%d partial copy of pointer\n", insn->src_reg); return -EACCES; } mark_reg_unknown(env, regs, insn->dst_reg); coerce_reg_to_size(®s[insn->dst_reg], 4); } } else { /* case: R = imm * remember the value we stored into this reg */ /* clear any state __mark_reg_known doesn't set */ mark_reg_unknown(env, regs, insn->dst_reg); regs[insn->dst_reg].type = SCALAR_VALUE; if (BPF_CLASS(insn->code) == BPF_ALU64) { __mark_reg_known(regs + insn->dst_reg, insn->imm); } else { __mark_reg_known(regs + insn->dst_reg, (u32)insn->imm); } } } else if (opcode > BPF_END) { verbose(env, "invalid BPF_ALU opcode %x\n", opcode); return -EINVAL; } else { /* all other ALU ops: and, sub, xor, add, ... */ if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0 || insn->off != 0) { verbose(env, "BPF_ALU uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; } else { if (insn->src_reg != BPF_REG_0 || insn->off != 0) { verbose(env, "BPF_ALU uses reserved fields\n"); return -EINVAL; } } /* check src2 operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; if ((opcode == BPF_MOD || opcode == BPF_DIV) && BPF_SRC(insn->code) == BPF_K && insn->imm == 0) { verbose(env, "div by zero\n"); return -EINVAL; } if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) { verbose(env, "BPF_ARSH not supported for 32 bit ALU\n"); return -EINVAL; } if ((opcode == BPF_LSH || opcode == BPF_RSH || opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; if (insn->imm < 0 || insn->imm >= size) { verbose(env, "invalid shift %d\n", insn->imm); return -EINVAL; } } /* check dest operand */ err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK); if (err) return err; return adjust_reg_min_max_vals(env, insn); } return 0; } static void find_good_pkt_pointers(struct bpf_verifier_state *vstate, struct bpf_reg_state *dst_reg, enum bpf_reg_type type, bool range_right_open) { struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *regs = state->regs, *reg; u16 new_range; int i, j; if (dst_reg->off < 0 || (dst_reg->off == 0 && range_right_open)) /* This doesn't give us any range */ return; if (dst_reg->umax_value > MAX_PACKET_OFF || dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF) /* Risk of overflow. For instance, ptr + (1<<63) may be less * than pkt_end, but that's because it's also less than pkt. */ return; new_range = dst_reg->off; if (range_right_open) new_range--; /* Examples for register markings: * * pkt_data in dst register: * * r2 = r3; * r2 += 8; * if (r2 > pkt_end) goto <handle exception> * <access okay> * * r2 = r3; * r2 += 8; * if (r2 < pkt_end) goto <access okay> * <handle exception> * * Where: * r2 == dst_reg, pkt_end == src_reg * r2=pkt(id=n,off=8,r=0) * r3=pkt(id=n,off=0,r=0) * * pkt_data in src register: * * r2 = r3; * r2 += 8; * if (pkt_end >= r2) goto <access okay> * <handle exception> * * r2 = r3; * r2 += 8; * if (pkt_end <= r2) goto <handle exception> * <access okay> * * Where: * pkt_end == dst_reg, r2 == src_reg * r2=pkt(id=n,off=8,r=0) * r3=pkt(id=n,off=0,r=0) * * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8) * or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8) * and [r3, r3 + 8-1) respectively is safe to access depending on * the check. */ /* If our ids match, then we must have the same max_value. And we * don't care about the other reg's fixed offset, since if it's too big * the range won't allow anything. * dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16. */ for (i = 0; i < MAX_BPF_REG; i++) if (regs[i].type == type && regs[i].id == dst_reg->id) /* keep the maximum range already checked */ regs[i].range = max(regs[i].range, new_range); for (j = 0; j <= vstate->curframe; j++) { state = vstate->frame[j]; for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) { if (state->stack[i].slot_type[0] != STACK_SPILL) continue; reg = &state->stack[i].spilled_ptr; if (reg->type == type && reg->id == dst_reg->id) reg->range = max(reg->range, new_range); } } } /* Adjusts the register min/max values in the case that the dst_reg is the * variable register that we are working on, and src_reg is a constant or we're * simply doing a BPF_K check. * In JEQ/JNE cases we also adjust the var_off values. */ static void reg_set_min_max(struct bpf_reg_state *true_reg, struct bpf_reg_state *false_reg, u64 val, u8 opcode) { /* If the dst_reg is a pointer, we can't learn anything about its * variable offset from the compare (unless src_reg were a pointer into * the same object, but we don't bother with that. * Since false_reg and true_reg have the same type by construction, we * only need to check one of them for pointerness. */ if (__is_pointer_value(false, false_reg)) return; switch (opcode) { case BPF_JEQ: /* If this is false then we know nothing Jon Snow, but if it is * true then we know for sure. */ __mark_reg_known(true_reg, val); break; case BPF_JNE: /* If this is true we know nothing Jon Snow, but if it is false * we know the value for sure; */ __mark_reg_known(false_reg, val); break; case BPF_JGT: false_reg->umax_value = min(false_reg->umax_value, val); true_reg->umin_value = max(true_reg->umin_value, val + 1); break; case BPF_JSGT: false_reg->smax_value = min_t(s64, false_reg->smax_value, val); true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1); break; case BPF_JLT: false_reg->umin_value = max(false_reg->umin_value, val); true_reg->umax_value = min(true_reg->umax_value, val - 1); break; case BPF_JSLT: false_reg->smin_value = max_t(s64, false_reg->smin_value, val); true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1); break; case BPF_JGE: false_reg->umax_value = min(false_reg->umax_value, val - 1); true_reg->umin_value = max(true_reg->umin_value, val); break; case BPF_JSGE: false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1); true_reg->smin_value = max_t(s64, true_reg->smin_value, val); break; case BPF_JLE: false_reg->umin_value = max(false_reg->umin_value, val + 1); true_reg->umax_value = min(true_reg->umax_value, val); break; case BPF_JSLE: false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1); true_reg->smax_value = min_t(s64, true_reg->smax_value, val); break; default: break; } __reg_deduce_bounds(false_reg); __reg_deduce_bounds(true_reg); /* We might have learned some bits from the bounds. */ __reg_bound_offset(false_reg); __reg_bound_offset(true_reg); /* Intersecting with the old var_off might have improved our bounds * slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc), * then new var_off is (0; 0x7f...fc) which improves our umax. */ __update_reg_bounds(false_reg); __update_reg_bounds(true_reg); } /* Same as above, but for the case that dst_reg holds a constant and src_reg is * the variable reg. */ static void reg_set_min_max_inv(struct bpf_reg_state *true_reg, struct bpf_reg_state *false_reg, u64 val, u8 opcode) { if (__is_pointer_value(false, false_reg)) return; switch (opcode) { case BPF_JEQ: /* If this is false then we know nothing Jon Snow, but if it is * true then we know for sure. */ __mark_reg_known(true_reg, val); break; case BPF_JNE: /* If this is true we know nothing Jon Snow, but if it is false * we know the value for sure; */ __mark_reg_known(false_reg, val); break; case BPF_JGT: true_reg->umax_value = min(true_reg->umax_value, val - 1); false_reg->umin_value = max(false_reg->umin_value, val); break; case BPF_JSGT: true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1); false_reg->smin_value = max_t(s64, false_reg->smin_value, val); break; case BPF_JLT: true_reg->umin_value = max(true_reg->umin_value, val + 1); false_reg->umax_value = min(false_reg->umax_value, val); break; case BPF_JSLT: true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1); false_reg->smax_value = min_t(s64, false_reg->smax_value, val); break; case BPF_JGE: true_reg->umax_value = min(true_reg->umax_value, val); false_reg->umin_value = max(false_reg->umin_value, val + 1); break; case BPF_JSGE: true_reg->smax_value = min_t(s64, true_reg->smax_value, val); false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1); break; case BPF_JLE: true_reg->umin_value = max(true_reg->umin_value, val); false_reg->umax_value = min(false_reg->umax_value, val - 1); break; case BPF_JSLE: true_reg->smin_value = max_t(s64, true_reg->smin_value, val); false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1); break; default: break; } __reg_deduce_bounds(false_reg); __reg_deduce_bounds(true_reg); /* We might have learned some bits from the bounds. */ __reg_bound_offset(false_reg); __reg_bound_offset(true_reg); /* Intersecting with the old var_off might have improved our bounds * slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc), * then new var_off is (0; 0x7f...fc) which improves our umax. */ __update_reg_bounds(false_reg); __update_reg_bounds(true_reg); } /* Regs are known to be equal, so intersect their min/max/var_off */ static void __reg_combine_min_max(struct bpf_reg_state *src_reg, struct bpf_reg_state *dst_reg) { src_reg->umin_value = dst_reg->umin_value = max(src_reg->umin_value, dst_reg->umin_value); src_reg->umax_value = dst_reg->umax_value = min(src_reg->umax_value, dst_reg->umax_value); src_reg->smin_value = dst_reg->smin_value = max(src_reg->smin_value, dst_reg->smin_value); src_reg->smax_value = dst_reg->smax_value = min(src_reg->smax_value, dst_reg->smax_value); src_reg->var_off = dst_reg->var_off = tnum_intersect(src_reg->var_off, dst_reg->var_off); /* We might have learned new bounds from the var_off. */ __update_reg_bounds(src_reg); __update_reg_bounds(dst_reg); /* We might have learned something about the sign bit. */ __reg_deduce_bounds(src_reg); __reg_deduce_bounds(dst_reg); /* We might have learned some bits from the bounds. */ __reg_bound_offset(src_reg); __reg_bound_offset(dst_reg); /* Intersecting with the old var_off might have improved our bounds * slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc), * then new var_off is (0; 0x7f...fc) which improves our umax. */ __update_reg_bounds(src_reg); __update_reg_bounds(dst_reg); } static void reg_combine_min_max(struct bpf_reg_state *true_src, struct bpf_reg_state *true_dst, struct bpf_reg_state *false_src, struct bpf_reg_state *false_dst, u8 opcode) { switch (opcode) { case BPF_JEQ: __reg_combine_min_max(true_src, true_dst); break; case BPF_JNE: __reg_combine_min_max(false_src, false_dst); break; } } static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id, bool is_null) { struct bpf_reg_state *reg = ®s[regno]; if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) { /* Old offset (both fixed and variable parts) should * have been known-zero, because we don't allow pointer * arithmetic on pointers that might be NULL. */ if (WARN_ON_ONCE(reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0) || reg->off)) { __mark_reg_known_zero(reg); reg->off = 0; } if (is_null) { reg->type = SCALAR_VALUE; } else if (reg->map_ptr->inner_map_meta) { reg->type = CONST_PTR_TO_MAP; reg->map_ptr = reg->map_ptr->inner_map_meta; } else { reg->type = PTR_TO_MAP_VALUE; } /* We don't need id from this point onwards anymore, thus we * should better reset it, so that state pruning has chances * to take effect. */ reg->id = 0; } } /* The logic is similar to find_good_pkt_pointers(), both could eventually * be folded together at some point. */ static void mark_map_regs(struct bpf_verifier_state *vstate, u32 regno, bool is_null) { struct bpf_func_state *state = vstate->frame[vstate->curframe]; struct bpf_reg_state *regs = state->regs; u32 id = regs[regno].id; int i, j; for (i = 0; i < MAX_BPF_REG; i++) mark_map_reg(regs, i, id, is_null); for (j = 0; j <= vstate->curframe; j++) { state = vstate->frame[j]; for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) { if (state->stack[i].slot_type[0] != STACK_SPILL) continue; mark_map_reg(&state->stack[i].spilled_ptr, 0, id, is_null); } } } static bool try_match_pkt_pointers(const struct bpf_insn *insn, struct bpf_reg_state *dst_reg, struct bpf_reg_state *src_reg, struct bpf_verifier_state *this_branch, struct bpf_verifier_state *other_branch) { if (BPF_SRC(insn->code) != BPF_X) return false; switch (BPF_OP(insn->code)) { case BPF_JGT: if ((dst_reg->type == PTR_TO_PACKET && src_reg->type == PTR_TO_PACKET_END) || (dst_reg->type == PTR_TO_PACKET_META && reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) { /* pkt_data' > pkt_end, pkt_meta' > pkt_data */ find_good_pkt_pointers(this_branch, dst_reg, dst_reg->type, false); } else if ((dst_reg->type == PTR_TO_PACKET_END && src_reg->type == PTR_TO_PACKET) || (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) && src_reg->type == PTR_TO_PACKET_META)) { /* pkt_end > pkt_data', pkt_data > pkt_meta' */ find_good_pkt_pointers(other_branch, src_reg, src_reg->type, true); } else { return false; } break; case BPF_JLT: if ((dst_reg->type == PTR_TO_PACKET && src_reg->type == PTR_TO_PACKET_END) || (dst_reg->type == PTR_TO_PACKET_META && reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) { /* pkt_data' < pkt_end, pkt_meta' < pkt_data */ find_good_pkt_pointers(other_branch, dst_reg, dst_reg->type, true); } else if ((dst_reg->type == PTR_TO_PACKET_END && src_reg->type == PTR_TO_PACKET) || (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) && src_reg->type == PTR_TO_PACKET_META)) { /* pkt_end < pkt_data', pkt_data > pkt_meta' */ find_good_pkt_pointers(this_branch, src_reg, src_reg->type, false); } else { return false; } break; case BPF_JGE: if ((dst_reg->type == PTR_TO_PACKET && src_reg->type == PTR_TO_PACKET_END) || (dst_reg->type == PTR_TO_PACKET_META && reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) { /* pkt_data' >= pkt_end, pkt_meta' >= pkt_data */ find_good_pkt_pointers(this_branch, dst_reg, dst_reg->type, true); } else if ((dst_reg->type == PTR_TO_PACKET_END && src_reg->type == PTR_TO_PACKET) || (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) && src_reg->type == PTR_TO_PACKET_META)) { /* pkt_end >= pkt_data', pkt_data >= pkt_meta' */ find_good_pkt_pointers(other_branch, src_reg, src_reg->type, false); } else { return false; } break; case BPF_JLE: if ((dst_reg->type == PTR_TO_PACKET && src_reg->type == PTR_TO_PACKET_END) || (dst_reg->type == PTR_TO_PACKET_META && reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) { /* pkt_data' <= pkt_end, pkt_meta' <= pkt_data */ find_good_pkt_pointers(other_branch, dst_reg, dst_reg->type, false); } else if ((dst_reg->type == PTR_TO_PACKET_END && src_reg->type == PTR_TO_PACKET) || (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) && src_reg->type == PTR_TO_PACKET_META)) { /* pkt_end <= pkt_data', pkt_data <= pkt_meta' */ find_good_pkt_pointers(this_branch, src_reg, src_reg->type, true); } else { return false; } break; default: return false; } return true; } static int check_cond_jmp_op(struct bpf_verifier_env *env, struct bpf_insn *insn, int *insn_idx) { struct bpf_verifier_state *this_branch = env->cur_state; struct bpf_verifier_state *other_branch; struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs; struct bpf_reg_state *dst_reg, *other_branch_regs; u8 opcode = BPF_OP(insn->code); int err; if (opcode > BPF_JSLE) { verbose(env, "invalid BPF_JMP opcode %x\n", opcode); return -EINVAL; } if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0) { verbose(env, "BPF_JMP uses reserved fields\n"); return -EINVAL; } /* check src1 operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; if (is_pointer_value(env, insn->src_reg)) { verbose(env, "R%d pointer comparison prohibited\n", insn->src_reg); return -EACCES; } } else { if (insn->src_reg != BPF_REG_0) { verbose(env, "BPF_JMP uses reserved fields\n"); return -EINVAL; } } /* check src2 operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; dst_reg = ®s[insn->dst_reg]; /* detect if R == 0 where R was initialized to zero earlier */ if (BPF_SRC(insn->code) == BPF_K && (opcode == BPF_JEQ || opcode == BPF_JNE) && dst_reg->type == SCALAR_VALUE && tnum_is_const(dst_reg->var_off)) { if ((opcode == BPF_JEQ && dst_reg->var_off.value == insn->imm) || (opcode == BPF_JNE && dst_reg->var_off.value != insn->imm)) { /* if (imm == imm) goto pc+off; * only follow the goto, ignore fall-through */ *insn_idx += insn->off; return 0; } else { /* if (imm != imm) goto pc+off; * only follow fall-through branch, since * that's where the program will go */ return 0; } } other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx); if (!other_branch) return -EFAULT; other_branch_regs = other_branch->frame[other_branch->curframe]->regs; /* detect if we are comparing against a constant value so we can adjust * our min/max values for our dst register. * this is only legit if both are scalars (or pointers to the same * object, I suppose, but we don't support that right now), because * otherwise the different base pointers mean the offsets aren't * comparable. */ if (BPF_SRC(insn->code) == BPF_X) { if (dst_reg->type == SCALAR_VALUE && regs[insn->src_reg].type == SCALAR_VALUE) { if (tnum_is_const(regs[insn->src_reg].var_off)) reg_set_min_max(&other_branch_regs[insn->dst_reg], dst_reg, regs[insn->src_reg].var_off.value, opcode); else if (tnum_is_const(dst_reg->var_off)) reg_set_min_max_inv(&other_branch_regs[insn->src_reg], ®s[insn->src_reg], dst_reg->var_off.value, opcode); else if (opcode == BPF_JEQ || opcode == BPF_JNE) /* Comparing for equality, we can combine knowledge */ reg_combine_min_max(&other_branch_regs[insn->src_reg], &other_branch_regs[insn->dst_reg], ®s[insn->src_reg], ®s[insn->dst_reg], opcode); } } else if (dst_reg->type == SCALAR_VALUE) { reg_set_min_max(&other_branch_regs[insn->dst_reg], dst_reg, insn->imm, opcode); } /* detect if R == 0 where R is returned from bpf_map_lookup_elem() */ if (BPF_SRC(insn->code) == BPF_K && insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) && dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) { /* Mark all identical map registers in each branch as either * safe or unknown depending R == 0 or R != 0 conditional. */ mark_map_regs(this_branch, insn->dst_reg, opcode == BPF_JNE); mark_map_regs(other_branch, insn->dst_reg, opcode == BPF_JEQ); } else if (!try_match_pkt_pointers(insn, dst_reg, ®s[insn->src_reg], this_branch, other_branch) && is_pointer_value(env, insn->dst_reg)) { verbose(env, "R%d pointer comparison prohibited\n", insn->dst_reg); return -EACCES; } if (env->log.level) print_verifier_state(env, this_branch->frame[this_branch->curframe]); return 0; } /* return the map pointer stored inside BPF_LD_IMM64 instruction */ static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn) { u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32; return (struct bpf_map *) (unsigned long) imm64; } /* verify BPF_LD_IMM64 instruction */ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = cur_regs(env); int err; if (BPF_SIZE(insn->code) != BPF_DW) { verbose(env, "invalid BPF_LD_IMM insn\n"); return -EINVAL; } if (insn->off != 0) { verbose(env, "BPF_LD_IMM64 uses reserved fields\n"); return -EINVAL; } err = check_reg_arg(env, insn->dst_reg, DST_OP); if (err) return err; if (insn->src_reg == 0) { u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm; regs[insn->dst_reg].type = SCALAR_VALUE; __mark_reg_known(®s[insn->dst_reg], imm); return 0; } /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */ BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD); regs[insn->dst_reg].type = CONST_PTR_TO_MAP; regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn); return 0; } static bool may_access_skb(enum bpf_prog_type type) { switch (type) { case BPF_PROG_TYPE_SOCKET_FILTER: case BPF_PROG_TYPE_SCHED_CLS: case BPF_PROG_TYPE_SCHED_ACT: return true; default: return false; } } /* verify safety of LD_ABS|LD_IND instructions: * - they can only appear in the programs where ctx == skb * - since they are wrappers of function calls, they scratch R1-R5 registers, * preserve R6-R9, and store return value into R0 * * Implicit input: * ctx == skb == R6 == CTX * * Explicit input: * SRC == any register * IMM == 32-bit immediate * * Output: * R0 - 8/16/32-bit skb data converted to cpu endianness */ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) { struct bpf_reg_state *regs = cur_regs(env); u8 mode = BPF_MODE(insn->code); int i, err; if (!may_access_skb(env->prog->type)) { verbose(env, "BPF_LD_[ABS|IND] instructions not allowed for this program type\n"); return -EINVAL; } if (!env->ops->gen_ld_abs) { verbose(env, "bpf verifier is misconfigured\n"); return -EINVAL; } if (env->subprog_cnt > 1) { /* when program has LD_ABS insn JITs and interpreter assume * that r1 == ctx == skb which is not the case for callees * that can have arbitrary arguments. It's problematic * for main prog as well since JITs would need to analyze * all functions in order to make proper register save/restore * decisions in the main prog. Hence disallow LD_ABS with calls */ verbose(env, "BPF_LD_[ABS|IND] instructions cannot be mixed with bpf-to-bpf calls\n"); return -EINVAL; } if (insn->dst_reg != BPF_REG_0 || insn->off != 0 || BPF_SIZE(insn->code) == BPF_DW || (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) { verbose(env, "BPF_LD_[ABS|IND] uses reserved fields\n"); return -EINVAL; } /* check whether implicit source operand (register R6) is readable */ err = check_reg_arg(env, BPF_REG_6, SRC_OP); if (err) return err; if (regs[BPF_REG_6].type != PTR_TO_CTX) { verbose(env, "at the time of BPF_LD_ABS|IND R6 != pointer to skb\n"); return -EINVAL; } if (mode == BPF_IND) { /* check explicit source operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; } /* reset caller saved regs to unreadable */ for (i = 0; i < CALLER_SAVED_REGS; i++) { mark_reg_not_init(env, regs, caller_saved[i]); check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK); } /* mark destination R0 register as readable, since it contains * the value fetched from the packet. * Already marked as written above. */ mark_reg_unknown(env, regs, BPF_REG_0); return 0; } static int check_return_code(struct bpf_verifier_env *env) { struct bpf_reg_state *reg; struct tnum range = tnum_range(0, 1); switch (env->prog->type) { case BPF_PROG_TYPE_CGROUP_SKB: case BPF_PROG_TYPE_CGROUP_SOCK: case BPF_PROG_TYPE_CGROUP_SOCK_ADDR: case BPF_PROG_TYPE_SOCK_OPS: case BPF_PROG_TYPE_CGROUP_DEVICE: break; default: return 0; } reg = cur_regs(env) + BPF_REG_0; if (reg->type != SCALAR_VALUE) { verbose(env, "At program exit the register R0 is not a known value (%s)\n", reg_type_str[reg->type]); return -EINVAL; } if (!tnum_in(range, reg->var_off)) { verbose(env, "At program exit the register R0 "); if (!tnum_is_unknown(reg->var_off)) { char tn_buf[48]; tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); verbose(env, "has value %s", tn_buf); } else { verbose(env, "has unknown scalar value"); } verbose(env, " should have been 0 or 1\n"); return -EINVAL; } return 0; } /* non-recursive DFS pseudo code * 1 procedure DFS-iterative(G,v): * 2 label v as discovered * 3 let S be a stack * 4 S.push(v) * 5 while S is not empty * 6 t <- S.pop() * 7 if t is what we're looking for: * 8 return t * 9 for all edges e in G.adjacentEdges(t) do * 10 if edge e is already labelled * 11 continue with the next edge * 12 w <- G.adjacentVertex(t,e) * 13 if vertex w is not discovered and not explored * 14 label e as tree-edge * 15 label w as discovered * 16 S.push(w) * 17 continue at 5 * 18 else if vertex w is discovered * 19 label e as back-edge * 20 else * 21 // vertex w is explored * 22 label e as forward- or cross-edge * 23 label t as explored * 24 S.pop() * * convention: * 0x10 - discovered * 0x11 - discovered and fall-through edge labelled * 0x12 - discovered and fall-through and branch edges labelled * 0x20 - explored */ enum { DISCOVERED = 0x10, EXPLORED = 0x20, FALLTHROUGH = 1, BRANCH = 2, }; #define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L) static int *insn_stack; /* stack of insns to process */ static int cur_stack; /* current stack index */ static int *insn_state; /* t, w, e - match pseudo-code above: * t - index of current instruction * w - next instruction * e - edge */ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) { if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH)) return 0; if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH)) return 0; if (w < 0 || w >= env->prog->len) { verbose(env, "jump out of range from insn %d to %d\n", t, w); return -EINVAL; } if (e == BRANCH) /* mark branch target for state pruning */ env->explored_states[w] = STATE_LIST_MARK; if (insn_state[w] == 0) { /* tree-edge */ insn_state[t] = DISCOVERED | e; insn_state[w] = DISCOVERED; if (cur_stack >= env->prog->len) return -E2BIG; insn_stack[cur_stack++] = w; return 1; } else if ((insn_state[w] & 0xF0) == DISCOVERED) { verbose(env, "back-edge from insn %d to %d\n", t, w); return -EINVAL; } else if (insn_state[w] == EXPLORED) { /* forward- or cross-edge */ insn_state[t] = DISCOVERED | e; } else { verbose(env, "insn state internal bug\n"); return -EFAULT; } return 0; } /* non-recursive depth-first-search to detect loops in BPF program * loop == back-edge in directed graph */ static int check_cfg(struct bpf_verifier_env *env) { struct bpf_insn *insns = env->prog->insnsi; int insn_cnt = env->prog->len; int ret = 0; int i, t; ret = check_subprogs(env); if (ret < 0) return ret; insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_state) return -ENOMEM; insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_stack) { kfree(insn_state); return -ENOMEM; } insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */ insn_stack[0] = 0; /* 0 is the first instruction */ cur_stack = 1; peek_stack: if (cur_stack == 0) goto check_state; t = insn_stack[cur_stack - 1]; if (BPF_CLASS(insns[t].code) == BPF_JMP) { u8 opcode = BPF_OP(insns[t].code); if (opcode == BPF_EXIT) { goto mark_explored; } else if (opcode == BPF_CALL) { ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; if (t + 1 < insn_cnt) env->explored_states[t + 1] = STATE_LIST_MARK; if (insns[t].src_reg == BPF_PSEUDO_CALL) { env->explored_states[t] = STATE_LIST_MARK; ret = push_insn(t, t + insns[t].imm + 1, BRANCH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; } } else if (opcode == BPF_JA) { if (BPF_SRC(insns[t].code) != BPF_K) { ret = -EINVAL; goto err_free; } /* unconditional jump with single edge */ ret = push_insn(t, t + insns[t].off + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; /* tell verifier to check for equivalent states * after every call and jump */ if (t + 1 < insn_cnt) env->explored_states[t + 1] = STATE_LIST_MARK; } else { /* conditional jump with two edges */ env->explored_states[t] = STATE_LIST_MARK; ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; ret = push_insn(t, t + insns[t].off + 1, BRANCH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; } } else { /* all other non-branch instructions with single * fall-through edge */ ret = push_insn(t, t + 1, FALLTHROUGH, env); if (ret == 1) goto peek_stack; else if (ret < 0) goto err_free; } mark_explored: insn_state[t] = EXPLORED; if (cur_stack-- <= 0) { verbose(env, "pop stack internal bug\n"); ret = -EFAULT; goto err_free; } goto peek_stack; check_state: for (i = 0; i < insn_cnt; i++) { if (insn_state[i] != EXPLORED) { verbose(env, "unreachable insn %d\n", i); ret = -EINVAL; goto err_free; } } ret = 0; /* cfg looks good */ err_free: kfree(insn_state); kfree(insn_stack); return ret; } /* check %cur's range satisfies %old's */ static bool range_within(struct bpf_reg_state *old, struct bpf_reg_state *cur) { return old->umin_value <= cur->umin_value && old->umax_value >= cur->umax_value && old->smin_value <= cur->smin_value && old->smax_value >= cur->smax_value; } /* Maximum number of register states that can exist at once */ #define ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE) struct idpair { u32 old; u32 cur; }; /* If in the old state two registers had the same id, then they need to have * the same id in the new state as well. But that id could be different from * the old state, so we need to track the mapping from old to new ids. * Once we have seen that, say, a reg with old id 5 had new id 9, any subsequent * regs with old id 5 must also have new id 9 for the new state to be safe. But * regs with a different old id could still have new id 9, we don't care about * that. * So we look through our idmap to see if this old id has been seen before. If * so, we require the new id to match; otherwise, we add the id pair to the map. */ static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap) { unsigned int i; for (i = 0; i < ID_MAP_SIZE; i++) { if (!idmap[i].old) { /* Reached an empty slot; haven't seen this id before */ idmap[i].old = old_id; idmap[i].cur = cur_id; return true; } if (idmap[i].old == old_id) return idmap[i].cur == cur_id; } /* We ran out of idmap slots, which should be impossible */ WARN_ON_ONCE(1); return false; } /* Returns true if (rold safe implies rcur safe) */ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur, struct idpair *idmap) { bool equal; if (!(rold->live & REG_LIVE_READ)) /* explored state didn't use this */ return true; equal = memcmp(rold, rcur, offsetof(struct bpf_reg_state, frameno)) == 0; if (rold->type == PTR_TO_STACK) /* two stack pointers are equal only if they're pointing to * the same stack frame, since fp-8 in foo != fp-8 in bar */ return equal && rold->frameno == rcur->frameno; if (equal) return true; if (rold->type == NOT_INIT) /* explored state can't have used this */ return true; if (rcur->type == NOT_INIT) return false; switch (rold->type) { case SCALAR_VALUE: if (rcur->type == SCALAR_VALUE) { /* new val must satisfy old val knowledge */ return range_within(rold, rcur) && tnum_in(rold->var_off, rcur->var_off); } else { /* We're trying to use a pointer in place of a scalar. * Even if the scalar was unbounded, this could lead to * pointer leaks because scalars are allowed to leak * while pointers are not. We could make this safe in * special cases if root is calling us, but it's * probably not worth the hassle. */ return false; } case PTR_TO_MAP_VALUE: /* If the new min/max/var_off satisfy the old ones and * everything else matches, we are OK. * We don't care about the 'id' value, because nothing * uses it for PTR_TO_MAP_VALUE (only for ..._OR_NULL) */ return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 && range_within(rold, rcur) && tnum_in(rold->var_off, rcur->var_off); case PTR_TO_MAP_VALUE_OR_NULL: /* a PTR_TO_MAP_VALUE could be safe to use as a * PTR_TO_MAP_VALUE_OR_NULL into the same map. * However, if the old PTR_TO_MAP_VALUE_OR_NULL then got NULL- * checked, doing so could have affected others with the same * id, and we can't check for that because we lost the id when * we converted to a PTR_TO_MAP_VALUE. */ if (rcur->type != PTR_TO_MAP_VALUE_OR_NULL) return false; if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, id))) return false; /* Check our ids match any regs they're supposed to */ return check_ids(rold->id, rcur->id, idmap); case PTR_TO_PACKET_META: case PTR_TO_PACKET: if (rcur->type != rold->type) return false; /* We must have at least as much range as the old ptr * did, so that any accesses which were safe before are * still safe. This is true even if old range < old off, * since someone could have accessed through (ptr - k), or * even done ptr -= k in a register, to get a safe access. */ if (rold->range > rcur->range) return false; /* If the offsets don't match, we can't trust our alignment; * nor can we be sure that we won't fall out of range. */ if (rold->off != rcur->off) return false; /* id relations must be preserved */ if (rold->id && !check_ids(rold->id, rcur->id, idmap)) return false; /* new val must satisfy old val knowledge */ return range_within(rold, rcur) && tnum_in(rold->var_off, rcur->var_off); case PTR_TO_CTX: case CONST_PTR_TO_MAP: case PTR_TO_PACKET_END: /* Only valid matches are exact, which memcmp() above * would have accepted */ default: /* Don't know what's going on, just say it's not safe */ return false; } /* Shouldn't get here; if we do, say it's not safe */ WARN_ON_ONCE(1); return false; } static bool stacksafe(struct bpf_func_state *old, struct bpf_func_state *cur, struct idpair *idmap) { int i, spi; /* if explored stack has more populated slots than current stack * such stacks are not equivalent */ if (old->allocated_stack > cur->allocated_stack) return false; /* walk slots of the explored stack and ignore any additional * slots in the current stack, since explored(safe) state * didn't use them */ for (i = 0; i < old->allocated_stack; i++) { spi = i / BPF_REG_SIZE; if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ)) /* explored state didn't use this */ continue; if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID) continue; /* if old state was safe with misc data in the stack * it will be safe with zero-initialized stack. * The opposite is not true */ if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC && cur->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_ZERO) continue; if (old->stack[spi].slot_type[i % BPF_REG_SIZE] != cur->stack[spi].slot_type[i % BPF_REG_SIZE]) /* Ex: old explored (safe) state has STACK_SPILL in * this stack slot, but current has has STACK_MISC -> * this verifier states are not equivalent, * return false to continue verification of this path */ return false; if (i % BPF_REG_SIZE) continue; if (old->stack[spi].slot_type[0] != STACK_SPILL) continue; if (!regsafe(&old->stack[spi].spilled_ptr, &cur->stack[spi].spilled_ptr, idmap)) /* when explored and current stack slot are both storing * spilled registers, check that stored pointers types * are the same as well. * Ex: explored safe path could have stored * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -8} * but current path has stored: * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -16} * such verifier states are not equivalent. * return false to continue verification of this path */ return false; } return true; } /* compare two verifier states * * all states stored in state_list are known to be valid, since * verifier reached 'bpf_exit' instruction through them * * this function is called when verifier exploring different branches of * execution popped from the state stack. If it sees an old state that has * more strict register state and more strict stack state then this execution * branch doesn't need to be explored further, since verifier already * concluded that more strict state leads to valid finish. * * Therefore two states are equivalent if register state is more conservative * and explored stack state is more conservative than the current one. * Example: * explored current * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC) * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC) * * In other words if current stack state (one being explored) has more * valid slots than old one that already passed validation, it means * the verifier can stop exploring and conclude that current state is valid too * * Similarly with registers. If explored state has register type as invalid * whereas register type in current state is meaningful, it means that * the current state will reach 'bpf_exit' instruction safely */ static bool func_states_equal(struct bpf_func_state *old, struct bpf_func_state *cur) { struct idpair *idmap; bool ret = false; int i; idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL); /* If we failed to allocate the idmap, just say it's not safe */ if (!idmap) return false; for (i = 0; i < MAX_BPF_REG; i++) { if (!regsafe(&old->regs[i], &cur->regs[i], idmap)) goto out_free; } if (!stacksafe(old, cur, idmap)) goto out_free; ret = true; out_free: kfree(idmap); return ret; } static bool states_equal(struct bpf_verifier_env *env, struct bpf_verifier_state *old, struct bpf_verifier_state *cur) { int i; if (old->curframe != cur->curframe) return false; /* for states to be equal callsites have to be the same * and all frame states need to be equivalent */ for (i = 0; i <= old->curframe; i++) { if (old->frame[i]->callsite != cur->frame[i]->callsite) return false; if (!func_states_equal(old->frame[i], cur->frame[i])) return false; } return true; } /* A write screens off any subsequent reads; but write marks come from the * straight-line code between a state and its parent. When we arrive at an * equivalent state (jump target or such) we didn't arrive by the straight-line * code, so read marks in the state must propagate to the parent regardless * of the state's write marks. That's what 'parent == state->parent' comparison * in mark_reg_read() and mark_stack_slot_read() is for. */ static int propagate_liveness(struct bpf_verifier_env *env, const struct bpf_verifier_state *vstate, struct bpf_verifier_state *vparent) { int i, frame, err = 0; struct bpf_func_state *state, *parent; if (vparent->curframe != vstate->curframe) { WARN(1, "propagate_live: parent frame %d current frame %d\n", vparent->curframe, vstate->curframe); return -EFAULT; } /* Propagate read liveness of registers... */ BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG); /* We don't need to worry about FP liveness because it's read-only */ for (i = 0; i < BPF_REG_FP; i++) { if (vparent->frame[vparent->curframe]->regs[i].live & REG_LIVE_READ) continue; if (vstate->frame[vstate->curframe]->regs[i].live & REG_LIVE_READ) { err = mark_reg_read(env, vstate, vparent, i); if (err) return err; } } /* ... and stack slots */ for (frame = 0; frame <= vstate->curframe; frame++) { state = vstate->frame[frame]; parent = vparent->frame[frame]; for (i = 0; i < state->allocated_stack / BPF_REG_SIZE && i < parent->allocated_stack / BPF_REG_SIZE; i++) { if (parent->stack[i].spilled_ptr.live & REG_LIVE_READ) continue; if (state->stack[i].spilled_ptr.live & REG_LIVE_READ) mark_stack_slot_read(env, vstate, vparent, i, frame); } } return err; } static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) { struct bpf_verifier_state_list *new_sl; struct bpf_verifier_state_list *sl; struct bpf_verifier_state *cur = env->cur_state; int i, j, err; sl = env->explored_states[insn_idx]; if (!sl) /* this 'insn_idx' instruction wasn't marked, so we will not * be doing state search here */ return 0; while (sl != STATE_LIST_MARK) { if (states_equal(env, &sl->state, cur)) { /* reached equivalent register/stack state, * prune the search. * Registers read by the continuation are read by us. * If we have any write marks in env->cur_state, they * will prevent corresponding reads in the continuation * from reaching our parent (an explored_state). Our * own state will get the read marks recorded, but * they'll be immediately forgotten as we're pruning * this state and will pop a new one. */ err = propagate_liveness(env, &sl->state, cur); if (err) return err; return 1; } sl = sl->next; } /* there were no equivalent states, remember current one. * technically the current state is not proven to be safe yet, * but it will either reach outer most bpf_exit (which means it's safe) * or it will be rejected. Since there are no loops, we won't be * seeing this tuple (frame[0].callsite, frame[1].callsite, .. insn_idx) * again on the way to bpf_exit */ new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL); if (!new_sl) return -ENOMEM; /* add new state to the head of linked list */ err = copy_verifier_state(&new_sl->state, cur); if (err) { free_verifier_state(&new_sl->state, false); kfree(new_sl); return err; } new_sl->next = env->explored_states[insn_idx]; env->explored_states[insn_idx] = new_sl; /* connect new state to parentage chain */ cur->parent = &new_sl->state; /* clear write marks in current state: the writes we did are not writes * our child did, so they don't screen off its reads from us. * (There are no read marks in current state, because reads always mark * their parent and current state never has children yet. Only * explored_states can get read marks.) */ for (i = 0; i < BPF_REG_FP; i++) cur->frame[cur->curframe]->regs[i].live = REG_LIVE_NONE; /* all stack frames are accessible from callee, clear them all */ for (j = 0; j <= cur->curframe; j++) { struct bpf_func_state *frame = cur->frame[j]; for (i = 0; i < frame->allocated_stack / BPF_REG_SIZE; i++) frame->stack[i].spilled_ptr.live = REG_LIVE_NONE; } return 0; } static int do_check(struct bpf_verifier_env *env) { struct bpf_verifier_state *state; struct bpf_insn *insns = env->prog->insnsi; struct bpf_reg_state *regs; int insn_cnt = env->prog->len, i; int insn_idx, prev_insn_idx = 0; int insn_processed = 0; bool do_print_state = false; state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL); if (!state) return -ENOMEM; state->curframe = 0; state->parent = NULL; state->frame[0] = kzalloc(sizeof(struct bpf_func_state), GFP_KERNEL); if (!state->frame[0]) { kfree(state); return -ENOMEM; } env->cur_state = state; init_func_state(env, state->frame[0], BPF_MAIN_FUNC /* callsite */, 0 /* frameno */, 0 /* subprogno, zero == main subprog */); insn_idx = 0; for (;;) { struct bpf_insn *insn; u8 class; int err; if (insn_idx >= insn_cnt) { verbose(env, "invalid insn idx %d insn_cnt %d\n", insn_idx, insn_cnt); return -EFAULT; } insn = &insns[insn_idx]; class = BPF_CLASS(insn->code); if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) { verbose(env, "BPF program is too large. Processed %d insn\n", insn_processed); return -E2BIG; } err = is_state_visited(env, insn_idx); if (err < 0) return err; if (err == 1) { /* found equivalent state, can prune the search */ if (env->log.level) { if (do_print_state) verbose(env, "\nfrom %d to %d: safe\n", prev_insn_idx, insn_idx); else verbose(env, "%d: safe\n", insn_idx); } goto process_bpf_exit; } if (need_resched()) cond_resched(); if (env->log.level > 1 || (env->log.level && do_print_state)) { if (env->log.level > 1) verbose(env, "%d:", insn_idx); else verbose(env, "\nfrom %d to %d:", prev_insn_idx, insn_idx); print_verifier_state(env, state->frame[state->curframe]); do_print_state = false; } if (env->log.level) { const struct bpf_insn_cbs cbs = { .cb_print = verbose, .private_data = env, }; verbose(env, "%d: ", insn_idx); print_bpf_insn(&cbs, insn, env->allow_ptr_leaks); } if (bpf_prog_is_dev_bound(env->prog->aux)) { err = bpf_prog_offload_verify_insn(env, insn_idx, prev_insn_idx); if (err) return err; } regs = cur_regs(env); env->insn_aux_data[insn_idx].seen = true; if (class == BPF_ALU || class == BPF_ALU64) { err = check_alu_op(env, insn); if (err) return err; } else if (class == BPF_LDX) { enum bpf_reg_type *prev_src_type, src_reg_type; /* check for reserved fields is already done */ /* check src operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK); if (err) return err; src_reg_type = regs[insn->src_reg].type; /* check that memory (src_reg + off) is readable, * the state of dst_reg will be updated by this func */ err = check_mem_access(env, insn_idx, insn->src_reg, insn->off, BPF_SIZE(insn->code), BPF_READ, insn->dst_reg, false); if (err) return err; prev_src_type = &env->insn_aux_data[insn_idx].ptr_type; if (*prev_src_type == NOT_INIT) { /* saw a valid insn * dst_reg = *(u32 *)(src_reg + off) * save type to validate intersecting paths */ *prev_src_type = src_reg_type; } else if (src_reg_type != *prev_src_type && (src_reg_type == PTR_TO_CTX || *prev_src_type == PTR_TO_CTX)) { /* ABuser program is trying to use the same insn * dst_reg = *(u32*) (src_reg + off) * with different pointer types: * src_reg == ctx in one branch and * src_reg == stack|map in some other branch. * Reject it. */ verbose(env, "same insn cannot be used with different pointers\n"); return -EINVAL; } } else if (class == BPF_STX) { enum bpf_reg_type *prev_dst_type, dst_reg_type; if (BPF_MODE(insn->code) == BPF_XADD) { err = check_xadd(env, insn_idx, insn); if (err) return err; insn_idx++; continue; } /* check src1 operand */ err = check_reg_arg(env, insn->src_reg, SRC_OP); if (err) return err; /* check src2 operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; dst_reg_type = regs[insn->dst_reg].type; /* check that memory (dst_reg + off) is writeable */ err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, insn->src_reg, false); if (err) return err; prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type; if (*prev_dst_type == NOT_INIT) { *prev_dst_type = dst_reg_type; } else if (dst_reg_type != *prev_dst_type && (dst_reg_type == PTR_TO_CTX || *prev_dst_type == PTR_TO_CTX)) { verbose(env, "same insn cannot be used with different pointers\n"); return -EINVAL; } } else if (class == BPF_ST) { if (BPF_MODE(insn->code) != BPF_MEM || insn->src_reg != BPF_REG_0) { verbose(env, "BPF_ST uses reserved fields\n"); return -EINVAL; } /* check src operand */ err = check_reg_arg(env, insn->dst_reg, SRC_OP); if (err) return err; if (is_ctx_reg(env, insn->dst_reg)) { verbose(env, "BPF_ST stores into R%d context is not allowed\n", insn->dst_reg); return -EACCES; } /* check that memory (dst_reg + off) is writeable */ err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off, BPF_SIZE(insn->code), BPF_WRITE, -1, false); if (err) return err; } else if (class == BPF_JMP) { u8 opcode = BPF_OP(insn->code); if (opcode == BPF_CALL) { if (BPF_SRC(insn->code) != BPF_K || insn->off != 0 || (insn->src_reg != BPF_REG_0 && insn->src_reg != BPF_PSEUDO_CALL) || insn->dst_reg != BPF_REG_0) { verbose(env, "BPF_CALL uses reserved fields\n"); return -EINVAL; } if (insn->src_reg == BPF_PSEUDO_CALL) err = check_func_call(env, insn, &insn_idx); else err = check_helper_call(env, insn->imm, insn_idx); if (err) return err; } else if (opcode == BPF_JA) { if (BPF_SRC(insn->code) != BPF_K || insn->imm != 0 || insn->src_reg != BPF_REG_0 || insn->dst_reg != BPF_REG_0) { verbose(env, "BPF_JA uses reserved fields\n"); return -EINVAL; } insn_idx += insn->off + 1; continue; } else if (opcode == BPF_EXIT) { if (BPF_SRC(insn->code) != BPF_K || insn->imm != 0 || insn->src_reg != BPF_REG_0 || insn->dst_reg != BPF_REG_0) { verbose(env, "BPF_EXIT uses reserved fields\n"); return -EINVAL; } if (state->curframe) { /* exit from nested function */ prev_insn_idx = insn_idx; err = prepare_func_exit(env, &insn_idx); if (err) return err; do_print_state = true; continue; } /* eBPF calling convetion is such that R0 is used * to return the value from eBPF program. * Make sure that it's readable at this time * of bpf_exit, which means that program wrote * something into it earlier */ err = check_reg_arg(env, BPF_REG_0, SRC_OP); if (err) return err; if (is_pointer_value(env, BPF_REG_0)) { verbose(env, "R0 leaks addr as return value\n"); return -EACCES; } err = check_return_code(env); if (err) return err; process_bpf_exit: err = pop_stack(env, &prev_insn_idx, &insn_idx); if (err < 0) { if (err != -ENOENT) return err; break; } else { do_print_state = true; continue; } } else { err = check_cond_jmp_op(env, insn, &insn_idx); if (err) return err; } } else if (class == BPF_LD) { u8 mode = BPF_MODE(insn->code); if (mode == BPF_ABS || mode == BPF_IND) { err = check_ld_abs(env, insn); if (err) return err; } else if (mode == BPF_IMM) { err = check_ld_imm(env, insn); if (err) return err; insn_idx++; env->insn_aux_data[insn_idx].seen = true; } else { verbose(env, "invalid BPF_LD mode\n"); return -EINVAL; } } else { verbose(env, "unknown insn class %d\n", class); return -EINVAL; } insn_idx++; } verbose(env, "processed %d insns (limit %d), stack depth ", insn_processed, BPF_COMPLEXITY_LIMIT_INSNS); for (i = 0; i < env->subprog_cnt; i++) { u32 depth = env->subprog_info[i].stack_depth; verbose(env, "%d", depth); if (i + 1 < env->subprog_cnt) verbose(env, "+"); } verbose(env, "\n"); env->prog->aux->stack_depth = env->subprog_info[0].stack_depth; return 0; } static int check_map_prealloc(struct bpf_map *map) { return (map->map_type != BPF_MAP_TYPE_HASH && map->map_type != BPF_MAP_TYPE_PERCPU_HASH && map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) || !(map->map_flags & BPF_F_NO_PREALLOC); } static int check_map_prog_compatibility(struct bpf_verifier_env *env, struct bpf_map *map, struct bpf_prog *prog) { /* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use * preallocated hash maps, since doing memory allocation * in overflow_handler can crash depending on where nmi got * triggered. */ if (prog->type == BPF_PROG_TYPE_PERF_EVENT) { if (!check_map_prealloc(map)) { verbose(env, "perf_event programs can only use preallocated hash map\n"); return -EINVAL; } if (map->inner_map_meta && !check_map_prealloc(map->inner_map_meta)) { verbose(env, "perf_event programs can only use preallocated inner hash map\n"); return -EINVAL; } } if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) && !bpf_offload_prog_map_match(prog, map)) { verbose(env, "offload device mismatch between prog and map\n"); return -EINVAL; } return 0; } /* look for pseudo eBPF instructions that access map FDs and * replace them with actual map pointers */ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) { struct bpf_insn *insn = env->prog->insnsi; int insn_cnt = env->prog->len; int i, j, err; err = bpf_prog_calc_tag(env->prog); if (err) return err; for (i = 0; i < insn_cnt; i++, insn++) { if (BPF_CLASS(insn->code) == BPF_LDX && (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) { verbose(env, "BPF_LDX uses reserved fields\n"); return -EINVAL; } if (BPF_CLASS(insn->code) == BPF_STX && ((BPF_MODE(insn->code) != BPF_MEM && BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) { verbose(env, "BPF_STX uses reserved fields\n"); return -EINVAL; } if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) { struct bpf_map *map; struct fd f; if (i == insn_cnt - 1 || insn[1].code != 0 || insn[1].dst_reg != 0 || insn[1].src_reg != 0 || insn[1].off != 0) { verbose(env, "invalid bpf_ld_imm64 insn\n"); return -EINVAL; } if (insn->src_reg == 0) /* valid generic load 64-bit imm */ goto next_insn; if (insn->src_reg != BPF_PSEUDO_MAP_FD) { verbose(env, "unrecognized bpf_ld_imm64 insn\n"); return -EINVAL; } f = fdget(insn->imm); map = __bpf_map_get(f); if (IS_ERR(map)) { verbose(env, "fd %d is not pointing to valid bpf_map\n", insn->imm); return PTR_ERR(map); } err = check_map_prog_compatibility(env, map, env->prog); if (err) { fdput(f); return err; } /* store map pointer inside BPF_LD_IMM64 instruction */ insn[0].imm = (u32) (unsigned long) map; insn[1].imm = ((u64) (unsigned long) map) >> 32; /* check whether we recorded this map already */ for (j = 0; j < env->used_map_cnt; j++) if (env->used_maps[j] == map) { fdput(f); goto next_insn; } if (env->used_map_cnt >= MAX_USED_MAPS) { fdput(f); return -E2BIG; } /* hold the map. If the program is rejected by verifier, * the map will be released by release_maps() or it * will be used by the valid program until it's unloaded * and all maps are released in free_used_maps() */ map = bpf_map_inc(map, false); if (IS_ERR(map)) { fdput(f); return PTR_ERR(map); } env->used_maps[env->used_map_cnt++] = map; if (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE && bpf_cgroup_storage_assign(env->prog, map)) { verbose(env, "only one cgroup storage is allowed\n"); fdput(f); return -EBUSY; } fdput(f); next_insn: insn++; i++; continue; } /* Basic sanity check before we invest more work here. */ if (!bpf_opcode_in_insntable(insn->code)) { verbose(env, "unknown opcode %02x\n", insn->code); return -EINVAL; } } /* now all pseudo BPF_LD_IMM64 instructions load valid * 'struct bpf_map *' into a register instead of user map_fd. * These pointers will be used later by verifier to validate map access. */ return 0; } /* drop refcnt of maps used by the rejected program */ static void release_maps(struct bpf_verifier_env *env) { int i; if (env->prog->aux->cgroup_storage) bpf_cgroup_storage_release(env->prog, env->prog->aux->cgroup_storage); for (i = 0; i < env->used_map_cnt; i++) bpf_map_put(env->used_maps[i]); } /* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */ static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env) { struct bpf_insn *insn = env->prog->insnsi; int insn_cnt = env->prog->len; int i; for (i = 0; i < insn_cnt; i++, insn++) if (insn->code == (BPF_LD | BPF_IMM | BPF_DW)) insn->src_reg = 0; } /* single env->prog->insni[off] instruction was replaced with the range * insni[off, off + cnt). Adjust corresponding insn_aux_data by copying * [0, off) and [off, end) to new locations, so the patched range stays zero */ static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len, u32 off, u32 cnt) { struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data; int i; if (cnt == 1) return 0; new_data = vzalloc(array_size(prog_len, sizeof(struct bpf_insn_aux_data))); if (!new_data) return -ENOMEM; memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off); memcpy(new_data + off + cnt - 1, old_data + off, sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1)); for (i = off; i < off + cnt - 1; i++) new_data[i].seen = true; env->insn_aux_data = new_data; vfree(old_data); return 0; } static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len) { int i; if (len == 1) return; /* NOTE: fake 'exit' subprog should be updated as well. */ for (i = 0; i <= env->subprog_cnt; i++) { if (env->subprog_info[i].start < off) continue; env->subprog_info[i].start += len - 1; } } static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off, const struct bpf_insn *patch, u32 len) { struct bpf_prog *new_prog; new_prog = bpf_patch_insn_single(env->prog, off, patch, len); if (!new_prog) return NULL; if (adjust_insn_aux_data(env, new_prog->len, off, len)) return NULL; adjust_subprog_starts(env, off, len); return new_prog; } /* The verifier does more data flow analysis than llvm and will not * explore branches that are dead at run time. Malicious programs can * have dead code too. Therefore replace all dead at-run-time code * with 'ja -1'. * * Just nops are not optimal, e.g. if they would sit at the end of the * program and through another bug we would manage to jump there, then * we'd execute beyond program memory otherwise. Returning exception * code also wouldn't work since we can have subprogs where the dead * code could be located. */ static void sanitize_dead_code(struct bpf_verifier_env *env) { struct bpf_insn_aux_data *aux_data = env->insn_aux_data; struct bpf_insn trap = BPF_JMP_IMM(BPF_JA, 0, 0, -1); struct bpf_insn *insn = env->prog->insnsi; const int insn_cnt = env->prog->len; int i; for (i = 0; i < insn_cnt; i++) { if (aux_data[i].seen) continue; memcpy(insn + i, &trap, sizeof(trap)); } } /* convert load instructions that access fields of 'struct __sk_buff' * into sequence of instructions that access fields of 'struct sk_buff' */ static int convert_ctx_accesses(struct bpf_verifier_env *env) { const struct bpf_verifier_ops *ops = env->ops; int i, cnt, size, ctx_field_size, delta = 0; const int insn_cnt = env->prog->len; struct bpf_insn insn_buf[16], *insn; struct bpf_prog *new_prog; enum bpf_access_type type; bool is_narrower_load; u32 target_size; if (ops->gen_prologue) { cnt = ops->gen_prologue(insn_buf, env->seen_direct_write, env->prog); if (cnt >= ARRAY_SIZE(insn_buf)) { verbose(env, "bpf verifier is misconfigured\n"); return -EINVAL; } else if (cnt) { new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt); if (!new_prog) return -ENOMEM; env->prog = new_prog; delta += cnt - 1; } } if (!ops->convert_ctx_access || bpf_prog_is_dev_bound(env->prog->aux)) return 0; insn = env->prog->insnsi + delta; for (i = 0; i < insn_cnt; i++, insn++) { if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) || insn->code == (BPF_LDX | BPF_MEM | BPF_H) || insn->code == (BPF_LDX | BPF_MEM | BPF_W) || insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) type = BPF_READ; else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || insn->code == (BPF_STX | BPF_MEM | BPF_H) || insn->code == (BPF_STX | BPF_MEM | BPF_W) || insn->code == (BPF_STX | BPF_MEM | BPF_DW)) type = BPF_WRITE; else continue; if (type == BPF_WRITE && env->insn_aux_data[i + delta].sanitize_stack_off) { struct bpf_insn patch[] = { /* Sanitize suspicious stack slot with zero. * There are no memory dependencies for this store, * since it's only using frame pointer and immediate * constant of zero */ BPF_ST_MEM(BPF_DW, BPF_REG_FP, env->insn_aux_data[i + delta].sanitize_stack_off, 0), /* the original STX instruction will immediately * overwrite the same stack slot with appropriate value */ *insn, }; cnt = ARRAY_SIZE(patch); new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; env->prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX) continue; ctx_field_size = env->insn_aux_data[i + delta].ctx_field_size; size = BPF_LDST_BYTES(insn); /* If the read access is a narrower load of the field, * convert to a 4/8-byte load, to minimum program type specific * convert_ctx_access changes. If conversion is successful, * we will apply proper mask to the result. */ is_narrower_load = size < ctx_field_size; if (is_narrower_load) { u32 size_default = bpf_ctx_off_adjust_machine(ctx_field_size); u32 off = insn->off; u8 size_code; if (type == BPF_WRITE) { verbose(env, "bpf verifier narrow ctx access misconfigured\n"); return -EINVAL; } size_code = BPF_H; if (ctx_field_size == 4) size_code = BPF_W; else if (ctx_field_size == 8) size_code = BPF_DW; insn->off = off & ~(size_default - 1); insn->code = BPF_LDX | BPF_MEM | size_code; } target_size = 0; cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog, &target_size); if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) || (ctx_field_size && !target_size)) { verbose(env, "bpf verifier is misconfigured\n"); return -EINVAL; } if (is_narrower_load && size < target_size) { if (ctx_field_size <= 4) insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg, (1 << size * 8) - 1); else insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg, (1 << size * 8) - 1); } new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; /* keep walking new program and skip insns we just inserted */ env->prog = new_prog; insn = new_prog->insnsi + i + delta; } return 0; } static int jit_subprogs(struct bpf_verifier_env *env) { struct bpf_prog *prog = env->prog, **func, *tmp; int i, j, subprog_start, subprog_end = 0, len, subprog; struct bpf_insn *insn; void *old_bpf_func; int err = -ENOMEM; if (env->subprog_cnt <= 1) return 0; for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL) || insn->src_reg != BPF_PSEUDO_CALL) continue; /* Upon error here we cannot fall back to interpreter but * need a hard reject of the program. Thus -EFAULT is * propagated in any case. */ subprog = find_subprog(env, i + insn->imm + 1); if (subprog < 0) { WARN_ONCE(1, "verifier bug. No program starts at insn %d\n", i + insn->imm + 1); return -EFAULT; } /* temporarily remember subprog id inside insn instead of * aux_data, since next loop will split up all insns into funcs */ insn->off = subprog; /* remember original imm in case JIT fails and fallback * to interpreter will be needed */ env->insn_aux_data[i].call_imm = insn->imm; /* point imm to __bpf_call_base+1 from JITs point of view */ insn->imm = 1; } func = kcalloc(env->subprog_cnt, sizeof(prog), GFP_KERNEL); if (!func) goto out_undo_insn; for (i = 0; i < env->subprog_cnt; i++) { subprog_start = subprog_end; subprog_end = env->subprog_info[i + 1].start; len = subprog_end - subprog_start; func[i] = bpf_prog_alloc(bpf_prog_size(len), GFP_USER); if (!func[i]) goto out_free; memcpy(func[i]->insnsi, &prog->insnsi[subprog_start], len * sizeof(struct bpf_insn)); func[i]->type = prog->type; func[i]->len = len; if (bpf_prog_calc_tag(func[i])) goto out_free; func[i]->is_func = 1; /* Use bpf_prog_F_tag to indicate functions in stack traces. * Long term would need debug info to populate names */ func[i]->aux->name[0] = 'F'; func[i]->aux->stack_depth = env->subprog_info[i].stack_depth; func[i]->jit_requested = 1; func[i] = bpf_int_jit_compile(func[i]); if (!func[i]->jited) { err = -ENOTSUPP; goto out_free; } cond_resched(); } /* at this point all bpf functions were successfully JITed * now populate all bpf_calls with correct addresses and * run last pass of JIT */ for (i = 0; i < env->subprog_cnt; i++) { insn = func[i]->insnsi; for (j = 0; j < func[i]->len; j++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL) || insn->src_reg != BPF_PSEUDO_CALL) continue; subprog = insn->off; insn->imm = (u64 (*)(u64, u64, u64, u64, u64)) func[subprog]->bpf_func - __bpf_call_base; } /* we use the aux data to keep a list of the start addresses * of the JITed images for each function in the program * * for some architectures, such as powerpc64, the imm field * might not be large enough to hold the offset of the start * address of the callee's JITed image from __bpf_call_base * * in such cases, we can lookup the start address of a callee * by using its subprog id, available from the off field of * the call instruction, as an index for this list */ func[i]->aux->func = func; func[i]->aux->func_cnt = env->subprog_cnt; } for (i = 0; i < env->subprog_cnt; i++) { old_bpf_func = func[i]->bpf_func; tmp = bpf_int_jit_compile(func[i]); if (tmp != func[i] || func[i]->bpf_func != old_bpf_func) { verbose(env, "JIT doesn't support bpf-to-bpf calls\n"); err = -ENOTSUPP; goto out_free; } cond_resched(); } /* finally lock prog and jit images for all functions and * populate kallsysm */ for (i = 0; i < env->subprog_cnt; i++) { bpf_prog_lock_ro(func[i]); bpf_prog_kallsyms_add(func[i]); } /* Last step: make now unused interpreter insns from main * prog consistent for later dump requests, so they can * later look the same as if they were interpreted only. */ for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL) || insn->src_reg != BPF_PSEUDO_CALL) continue; insn->off = env->insn_aux_data[i].call_imm; subprog = find_subprog(env, i + insn->off + 1); insn->imm = subprog; } prog->jited = 1; prog->bpf_func = func[0]->bpf_func; prog->aux->func = func; prog->aux->func_cnt = env->subprog_cnt; return 0; out_free: for (i = 0; i < env->subprog_cnt; i++) if (func[i]) bpf_jit_free(func[i]); kfree(func); out_undo_insn: /* cleanup main prog to be interpreted */ prog->jit_requested = 0; for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL) || insn->src_reg != BPF_PSEUDO_CALL) continue; insn->off = 0; insn->imm = env->insn_aux_data[i].call_imm; } return err; } static int fixup_call_args(struct bpf_verifier_env *env) { #ifndef CONFIG_BPF_JIT_ALWAYS_ON struct bpf_prog *prog = env->prog; struct bpf_insn *insn = prog->insnsi; int i, depth; #endif int err; err = 0; if (env->prog->jit_requested) { err = jit_subprogs(env); if (err == 0) return 0; if (err == -EFAULT) return err; } #ifndef CONFIG_BPF_JIT_ALWAYS_ON for (i = 0; i < prog->len; i++, insn++) { if (insn->code != (BPF_JMP | BPF_CALL) || insn->src_reg != BPF_PSEUDO_CALL) continue; depth = get_callee_stack_depth(env, insn, i); if (depth < 0) return depth; bpf_patch_call_args(insn, depth); } err = 0; #endif return err; } /* fixup insn->imm field of bpf_call instructions * and inline eligible helpers as explicit sequence of BPF instructions * * this function is called after eBPF program passed verification */ static int fixup_bpf_calls(struct bpf_verifier_env *env) { struct bpf_prog *prog = env->prog; struct bpf_insn *insn = prog->insnsi; const struct bpf_func_proto *fn; const int insn_cnt = prog->len; const struct bpf_map_ops *ops; struct bpf_insn_aux_data *aux; struct bpf_insn insn_buf[16]; struct bpf_prog *new_prog; struct bpf_map *map_ptr; int i, cnt, delta = 0; for (i = 0; i < insn_cnt; i++, insn++) { if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) || insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) || insn->code == (BPF_ALU | BPF_MOD | BPF_X) || insn->code == (BPF_ALU | BPF_DIV | BPF_X)) { bool is64 = BPF_CLASS(insn->code) == BPF_ALU64; struct bpf_insn mask_and_div[] = { BPF_MOV32_REG(insn->src_reg, insn->src_reg), /* Rx div 0 -> 0 */ BPF_JMP_IMM(BPF_JNE, insn->src_reg, 0, 2), BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg), BPF_JMP_IMM(BPF_JA, 0, 0, 1), *insn, }; struct bpf_insn mask_and_mod[] = { BPF_MOV32_REG(insn->src_reg, insn->src_reg), /* Rx mod 0 -> Rx */ BPF_JMP_IMM(BPF_JEQ, insn->src_reg, 0, 1), *insn, }; struct bpf_insn *patchlet; if (insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) || insn->code == (BPF_ALU | BPF_DIV | BPF_X)) { patchlet = mask_and_div + (is64 ? 1 : 0); cnt = ARRAY_SIZE(mask_and_div) - (is64 ? 1 : 0); } else { patchlet = mask_and_mod + (is64 ? 1 : 0); cnt = ARRAY_SIZE(mask_and_mod) - (is64 ? 1 : 0); } new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; env->prog = prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } if (BPF_CLASS(insn->code) == BPF_LD && (BPF_MODE(insn->code) == BPF_ABS || BPF_MODE(insn->code) == BPF_IND)) { cnt = env->ops->gen_ld_abs(insn, insn_buf); if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { verbose(env, "bpf verifier is misconfigured\n"); return -EINVAL; } new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; env->prog = prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } if (insn->code != (BPF_JMP | BPF_CALL)) continue; if (insn->src_reg == BPF_PSEUDO_CALL) continue; if (insn->imm == BPF_FUNC_get_route_realm) prog->dst_needed = 1; if (insn->imm == BPF_FUNC_get_prandom_u32) bpf_user_rnd_init_once(); if (insn->imm == BPF_FUNC_override_return) prog->kprobe_override = 1; if (insn->imm == BPF_FUNC_tail_call) { /* If we tail call into other programs, we * cannot make any assumptions since they can * be replaced dynamically during runtime in * the program array. */ prog->cb_access = 1; env->prog->aux->stack_depth = MAX_BPF_STACK; /* mark bpf_tail_call as different opcode to avoid * conditional branch in the interpeter for every normal * call and to prevent accidental JITing by JIT compiler * that doesn't support bpf_tail_call yet */ insn->imm = 0; insn->code = BPF_JMP | BPF_TAIL_CALL; aux = &env->insn_aux_data[i + delta]; if (!bpf_map_ptr_unpriv(aux)) continue; /* instead of changing every JIT dealing with tail_call * emit two extra insns: * if (index >= max_entries) goto out; * index &= array->index_mask; * to avoid out-of-bounds cpu speculation */ if (bpf_map_ptr_poisoned(aux)) { verbose(env, "tail_call abusing map_ptr\n"); return -EINVAL; } map_ptr = BPF_MAP_PTR(aux->map_state); insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3, map_ptr->max_entries, 2); insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3, container_of(map_ptr, struct bpf_array, map)->index_mask); insn_buf[2] = *insn; cnt = 3; new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; env->prog = prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } /* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup * and other inlining handlers are currently limited to 64 bit * only. */ if (prog->jit_requested && BITS_PER_LONG == 64 && (insn->imm == BPF_FUNC_map_lookup_elem || insn->imm == BPF_FUNC_map_update_elem || insn->imm == BPF_FUNC_map_delete_elem)) { aux = &env->insn_aux_data[i + delta]; if (bpf_map_ptr_poisoned(aux)) goto patch_call_imm; map_ptr = BPF_MAP_PTR(aux->map_state); ops = map_ptr->ops; if (insn->imm == BPF_FUNC_map_lookup_elem && ops->map_gen_lookup) { cnt = ops->map_gen_lookup(map_ptr, insn_buf); if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) { verbose(env, "bpf verifier is misconfigured\n"); return -EINVAL; } new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM; delta += cnt - 1; env->prog = prog = new_prog; insn = new_prog->insnsi + i + delta; continue; } BUILD_BUG_ON(!__same_type(ops->map_lookup_elem, (void *(*)(struct bpf_map *map, void *key))NULL)); BUILD_BUG_ON(!__same_type(ops->map_delete_elem, (int (*)(struct bpf_map *map, void *key))NULL)); BUILD_BUG_ON(!__same_type(ops->map_update_elem, (int (*)(struct bpf_map *map, void *key, void *value, u64 flags))NULL)); switch (insn->imm) { case BPF_FUNC_map_lookup_elem: insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) - __bpf_call_base; continue; case BPF_FUNC_map_update_elem: insn->imm = BPF_CAST_CALL(ops->map_update_elem) - __bpf_call_base; continue; case BPF_FUNC_map_delete_elem: insn->imm = BPF_CAST_CALL(ops->map_delete_elem) - __bpf_call_base; continue; } goto patch_call_imm; } patch_call_imm: fn = env->ops->get_func_proto(insn->imm, env->prog); /* all functions that have prototype and verifier allowed * programs to call them, must be real in-kernel functions */ if (!fn->func) { verbose(env, "kernel subsystem misconfigured func %s#%d\n", func_id_name(insn->imm), insn->imm); return -EFAULT; } insn->imm = fn->func - __bpf_call_base; } return 0; } static void free_states(struct bpf_verifier_env *env) { struct bpf_verifier_state_list *sl, *sln; int i; if (!env->explored_states) return; for (i = 0; i < env->prog->len; i++) { sl = env->explored_states[i]; if (sl) while (sl != STATE_LIST_MARK) { sln = sl->next; free_verifier_state(&sl->state, false); kfree(sl); sl = sln; } } kfree(env->explored_states); } int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) { struct bpf_verifier_env *env; struct bpf_verifier_log *log; int ret = -EINVAL; /* no program is valid */ if (ARRAY_SIZE(bpf_verifier_ops) == 0) return -EINVAL; /* 'struct bpf_verifier_env' can be global, but since it's not small, * allocate/free it every time bpf_check() is called */ env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); if (!env) return -ENOMEM; log = &env->log; env->insn_aux_data = vzalloc(array_size(sizeof(struct bpf_insn_aux_data), (*prog)->len)); ret = -ENOMEM; if (!env->insn_aux_data) goto err_free_env; env->prog = *prog; env->ops = bpf_verifier_ops[env->prog->type]; /* grab the mutex to protect few globals used by verifier */ mutex_lock(&bpf_verifier_lock); if (attr->log_level || attr->log_buf || attr->log_size) { /* user requested verbose verifier output * and supplied buffer to store the verification trace */ log->level = attr->log_level; log->ubuf = (char __user *) (unsigned long) attr->log_buf; log->len_total = attr->log_size; ret = -EINVAL; /* log attributes have to be sane */ if (log->len_total < 128 || log->len_total > UINT_MAX >> 8 || !log->level || !log->ubuf) goto err_unlock; } env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT); if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) env->strict_alignment = true; ret = replace_map_fd_with_map_ptr(env); if (ret < 0) goto skip_full_check; if (bpf_prog_is_dev_bound(env->prog->aux)) { ret = bpf_prog_offload_verifier_prep(env); if (ret) goto skip_full_check; } env->explored_states = kcalloc(env->prog->len, sizeof(struct bpf_verifier_state_list *), GFP_USER); ret = -ENOMEM; if (!env->explored_states) goto skip_full_check; env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); ret = check_cfg(env); if (ret < 0) goto skip_full_check; ret = do_check(env); if (env->cur_state) { free_verifier_state(env->cur_state, true); env->cur_state = NULL; } skip_full_check: while (!pop_stack(env, NULL, NULL)); free_states(env); if (ret == 0) sanitize_dead_code(env); if (ret == 0) ret = check_max_stack_depth(env); if (ret == 0) /* program is valid, convert *(u32*)(ctx + off) accesses */ ret = convert_ctx_accesses(env); if (ret == 0) ret = fixup_bpf_calls(env); if (ret == 0) ret = fixup_call_args(env); if (log->level && bpf_verifier_log_full(log)) ret = -ENOSPC; if (log->level && !log->ubuf) { ret = -EFAULT; goto err_release_maps; } if (ret == 0 && env->used_map_cnt) { /* if program passed verifier, update used_maps in bpf_prog_info */ env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt, sizeof(env->used_maps[0]), GFP_KERNEL); if (!env->prog->aux->used_maps) { ret = -ENOMEM; goto err_release_maps; } memcpy(env->prog->aux->used_maps, env->used_maps, sizeof(env->used_maps[0]) * env->used_map_cnt); env->prog->aux->used_map_cnt = env->used_map_cnt; /* program is valid. Convert pseudo bpf_ld_imm64 into generic * bpf_ld_imm64 instructions */ convert_pseudo_ld_imm64(env); } err_release_maps: if (!env->prog->aux->used_maps) /* if we didn't copy map pointers into bpf_prog_info, release * them now. Otherwise free_used_maps() will release them. */ release_maps(env); *prog = env->prog; err_unlock: mutex_unlock(&bpf_verifier_lock); vfree(env->insn_aux_data); err_free_env: kfree(env); return ret; }
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