cregit-Linux how code gets into the kernel

Release 4.18 tools/testing/selftests/bpf/test_verifier_log.c

#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>

#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/unistd.h>

#include <bpf/bpf.h>

#include "bpf_rlimit.h"


#define LOG_SIZE (1 << 20)


#define err(str...)	printf("ERROR: " str)


static const struct bpf_insn code_sample[] = {
	/* We need a few instructions to pass the min log length */
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_MOV64_IMM(BPF_REG_0, 0),
	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
		     BPF_FUNC_map_lookup_elem),
	BPF_EXIT_INSN(),
};


static inline __u64 ptr_to_u64(const void *ptr) { return (__u64) (unsigned long) ptr; }

Contributors

PersonTokensPropCommitsCommitProp
Jakub Kiciński22100.00%1100.00%
Total22100.00%1100.00%


static int load(char *log, size_t log_len, int log_level) { union bpf_attr attr; bzero(&attr, sizeof(attr)); attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER; attr.insn_cnt = (__u32)(sizeof(code_sample) / sizeof(struct bpf_insn)); attr.insns = ptr_to_u64(code_sample); attr.license = ptr_to_u64("GPL"); attr.log_buf = ptr_to_u64(log); attr.log_size = log_len; attr.log_level = log_level; return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr)); }

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PersonTokensPropCommitsCommitProp
Jakub Kiciński112100.00%1100.00%
Total112100.00%1100.00%


static void check_ret(int ret, int exp_errno) { if (ret > 0) { close(ret); err("broken sample loaded successfully!?\n"); exit(1); } if (!ret || errno != exp_errno) { err("Program load returned: ret:%d/errno:%d, expected ret:%d/errno:%d\n", ret, errno, -1, exp_errno); exit(1); } }

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PersonTokensPropCommitsCommitProp
Jakub Kiciński65100.00%1100.00%
Total65100.00%1100.00%


static void check_ones(const char *buf, size_t len, const char *msg) { while (len--) if (buf[len] != 1) { err("%s", msg); exit(1); } }

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PersonTokensPropCommitsCommitProp
Jakub Kiciński47100.00%1100.00%
Total47100.00%1100.00%


static void test_log_good(char *log, size_t buf_len, size_t log_len, size_t exp_len, int exp_errno, const char *full_log) { size_t len; int ret; memset(log, 1, buf_len); ret = load(log, log_len, 1); check_ret(ret, exp_errno); len = strnlen(log, buf_len); if (len == buf_len) { err("verifier did not NULL terminate the log\n"); exit(1); } if (exp_len && len != exp_len) { err("incorrect log length expected:%zd have:%zd\n", exp_len, len); exit(1); } if (strchr(log, 1)) { err("verifier leaked a byte through\n"); exit(1); } check_ones(log + len + 1, buf_len - len - 1, "verifier wrote bytes past NULL termination\n"); if (memcmp(full_log, log, LOG_SIZE)) { err("log did not match expected output\n"); exit(1); } }

Contributors

PersonTokensPropCommitsCommitProp
Jakub Kiciński172100.00%1100.00%
Total172100.00%1100.00%


static void test_log_bad(char *log, size_t log_len, int log_level) { int ret; ret = load(log, log_len, log_level); check_ret(ret, EINVAL); if (log) check_ones(log, LOG_SIZE, "verifier touched log with bad parameters\n"); }

Contributors

PersonTokensPropCommitsCommitProp
Jakub Kiciński50100.00%1100.00%
Total50100.00%1100.00%


int main(int argc, char **argv) { char full_log[LOG_SIZE]; char log[LOG_SIZE]; size_t want_len; int i; memset(log, 1, LOG_SIZE); /* Test incorrect attr */ printf("Test log_level 0...\n"); test_log_bad(log, LOG_SIZE, 0); printf("Test log_size < 128...\n"); test_log_bad(log, 15, 1); printf("Test log_buff = NULL...\n"); test_log_bad(NULL, LOG_SIZE, 1); /* Test with log big enough */ printf("Test oversized buffer...\n"); test_log_good(full_log, LOG_SIZE, LOG_SIZE, 0, EACCES, full_log); want_len = strlen(full_log); printf("Test exact buffer...\n"); test_log_good(log, LOG_SIZE, want_len + 2, want_len, EACCES, full_log); printf("Test undersized buffers...\n"); for (i = 0; i < 64; i++) { full_log[want_len - i + 1] = 1; full_log[want_len - i] = 0; test_log_good(log, LOG_SIZE, want_len + 1 - i, want_len - i, ENOSPC, full_log); } printf("test_verifier_log: OK\n"); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Jakub Kiciński202100.00%1100.00%
Total202100.00%1100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Jakub Kiciński84598.83%133.33%
Daniel Borkmann50.58%133.33%
Yonghong Song50.58%133.33%
Total855100.00%3100.00%
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