cregit-Linux how code gets into the kernel

Release 4.15 kernel/seccomp.c

Directory: kernel
// SPDX-License-Identifier: GPL-2.0
/*
 * linux/kernel/seccomp.c
 *
 * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
 *
 * Copyright (C) 2012 Google, Inc.
 * Will Drewry <wad@chromium.org>
 *
 * This defines a simple but solid secure-computing facility.
 *
 * Mode 1 uses a fixed list of allowed system calls.
 * Mode 2 allows user-defined system call filters in the form
 *        of Berkeley Packet Filters/Linux Socket Filters.
 */

#include <linux/refcount.h>
#include <linux/audit.h>
#include <linux/compat.h>
#include <linux/coredump.h>
#include <linux/kmemleak.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/seccomp.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/sysctl.h>

#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
#include <asm/syscall.h>
#endif

#ifdef CONFIG_SECCOMP_FILTER
#include <linux/filter.h>
#include <linux/pid.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>

/**
 * struct seccomp_filter - container for seccomp BPF programs
 *
 * @usage: reference count to manage the object lifetime.
 *         get/put helpers should be used when accessing an instance
 *         outside of a lifetime-guarded section.  In general, this
 *         is only needed for handling filters shared across tasks.
 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
 * @prev: points to a previously installed, or inherited, filter
 * @prog: the BPF program to evaluate
 *
 * seccomp_filter objects are organized in a tree linked via the @prev
 * pointer.  For any task, it appears to be a singly-linked list starting
 * with current->seccomp.filter, the most recently attached or inherited filter.
 * However, multiple filters may share a @prev node, by way of fork(), which
 * results in a unidirectional tree existing in memory.  This is similar to
 * how namespaces work.
 *
 * seccomp_filter objects should never be modified after being attached
 * to a task_struct (other than @usage).
 */

struct seccomp_filter {
	
refcount_t usage;
	
bool log;
	
struct seccomp_filter *prev;
	
struct bpf_prog *prog;
};

/* Limit any path through the tree to 256KB worth of instructions. */

#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))

/*
 * Endianness is explicitly ignored and left for BPF program authors to manage
 * as per the specific architecture.
 */



static void populate_seccomp_data(struct seccomp_data *sd)
{
	struct task_struct *task = current;
	struct pt_regs *regs = task_pt_regs(task);
	unsigned long args[6];

	sd->nr = syscall_get_nr(task, regs);
	sd->arch = syscall_get_arch();
	syscall_get_arguments(task, regs, 0, 6, args);
	sd->args[0] = args[0];
	sd->args[1] = args[1];
	sd->args[2] = args[2];
	sd->args[3] = args[3];
	sd->args[4] = args[4];
	sd->args[5] = args[5];
	sd->instruction_pointer = KSTK_EIP(task);
}


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Eric Paris10.68%125.00%


Total147100.00%4100.00%



/**
 *      seccomp_check_filter - verify seccomp filter code
 *      @filter: filter to verify
 *      @flen: length of filter
 *
 * Takes a previously checked filter (by bpf_check_classic) and
 * redirects all filter code that loads struct sk_buff data
 * and related data through seccomp_bpf_load.  It also
 * enforces length and alignment checking of those loads.
 *
 * Returns 0 if the rule set is legal or -EINVAL if not.
 */



static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
{
	int pc;
	for (pc = 0; pc < flen; pc++) {
		struct sock_filter *ftest = &filter[pc];
		u16 code = ftest->code;
		u32 k = ftest->k;

		switch (code) {
		case BPF_LD | BPF_W | BPF_ABS:
			ftest->code = BPF_LDX | BPF_W | BPF_ABS;
			/* 32-bit aligned and not out of bounds. */
			if (k >= sizeof(struct seccomp_data) || k & 3)
				return -EINVAL;
			continue;
		case BPF_LD | BPF_W | BPF_LEN:
			ftest->code = BPF_LD | BPF_IMM;
			ftest->k = sizeof(struct seccomp_data);
			continue;
		case BPF_LDX | BPF_W | BPF_LEN:
			ftest->code = BPF_LDX | BPF_IMM;
			ftest->k = sizeof(struct seccomp_data);
			continue;
		/* Explicitly include allowed calls. */
		case BPF_RET | BPF_K:
		case BPF_RET | BPF_A:
		case BPF_ALU | BPF_ADD | BPF_K:
		case BPF_ALU | BPF_ADD | BPF_X:
		case BPF_ALU | BPF_SUB | BPF_K:
		case BPF_ALU | BPF_SUB | BPF_X:
		case BPF_ALU | BPF_MUL | BPF_K:
		case BPF_ALU | BPF_MUL | BPF_X:
		case BPF_ALU | BPF_DIV | BPF_K:
		case BPF_ALU | BPF_DIV | BPF_X:
		case BPF_ALU | BPF_AND | BPF_K:
		case BPF_ALU | BPF_AND | BPF_X:
		case BPF_ALU | BPF_OR | BPF_K:
		case BPF_ALU | BPF_OR | BPF_X:
		case BPF_ALU | BPF_XOR | BPF_K:
		case BPF_ALU | BPF_XOR | BPF_X:
		case BPF_ALU | BPF_LSH | BPF_K:
		case BPF_ALU | BPF_LSH | BPF_X:
		case BPF_ALU | BPF_RSH | BPF_K:
		case BPF_ALU | BPF_RSH | BPF_X:
		case BPF_ALU | BPF_NEG:
		case BPF_LD | BPF_IMM:
		case BPF_LDX | BPF_IMM:
		case BPF_MISC | BPF_TAX:
		case BPF_MISC | BPF_TXA:
		case BPF_LD | BPF_MEM:
		case BPF_LDX | BPF_MEM:
		case BPF_ST:
		case BPF_STX:
		case BPF_JMP | BPF_JA:
		case BPF_JMP | BPF_JEQ | BPF_K:
		case BPF_JMP | BPF_JEQ | BPF_X:
		case BPF_JMP | BPF_JGE | BPF_K:
		case BPF_JMP | BPF_JGE | BPF_X:
		case BPF_JMP | BPF_JGT | BPF_K:
		case BPF_JMP | BPF_JGT | BPF_X:
		case BPF_JMP | BPF_JSET | BPF_K:
		case BPF_JMP | BPF_JSET | BPF_X:
			continue;
		default:
			return -EINVAL;
		}
	}
	return 0;
}


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Alexei Starovoitov112.74%125.00%


Nicolas Schichan41.00%125.00%


Total401100.00%4100.00%



/**
 * seccomp_run_filters - evaluates all seccomp filters against @sd
 * @sd: optional seccomp data to be passed to filters
 * @match: stores struct seccomp_filter that resulted in the return value,
 *         unless filter returned SECCOMP_RET_ALLOW, in which case it will
 *         be unchanged.
 *
 * Returns valid seccomp BPF response codes.
 */

#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))



static u32 seccomp_run_filters(const struct seccomp_data *sd,
			       struct seccomp_filter **match)
{
	struct seccomp_data sd_local;
	u32 ret = SECCOMP_RET_ALLOW;
	/* Make sure cross-thread synced filter points somewhere sane. */
	struct seccomp_filter *f =
			READ_ONCE(current->seccomp.filter);

	/* Ensure unexpected behavior doesn't result in failing open. */
	if (unlikely(WARN_ON(f == NULL)))
		return SECCOMP_RET_KILL_PROCESS;

	if (!sd) {
		populate_seccomp_data(&sd_local);
		sd = &sd_local;
	}

	/*
         * All filters in the list are evaluated and the lowest BPF return
         * value always takes priority (ignoring the DATA).
         */
	for (; f; f = f->prev) {
		u32 cur_ret = BPF_PROG_RUN(f->prog, sd);

		if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
			ret = cur_ret;
			*match = f;
		}
	}
	return ret;
}

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Kees Cook3325.78%538.46%


Andrew Lutomirski1713.28%17.69%


Pranith Kumar107.81%17.69%


Alexei Starovoitov97.03%323.08%


Will Deacon10.78%17.69%


Total128100.00%13100.00%



#endif /* CONFIG_SECCOMP_FILTER */




static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
{
	assert_spin_locked(&current->sighand->siglock);

	if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
		return false;

	return true;
}


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Guenter Roeck12.33%133.33%


Total43100.00%3100.00%






static inline void seccomp_assign_mode(struct task_struct *task,
				       unsigned long seccomp_mode)
{
	assert_spin_locked(&task->sighand->siglock);

	task->seccomp.mode = seccomp_mode;
	/*
         * Make sure TIF_SECCOMP cannot be set before the mode (and
         * filter) is set.
         */
	smp_mb__before_atomic();
	set_tsk_thread_flag(task, TIF_SECCOMP);
}


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Guenter Roeck12.22%125.00%


Total45100.00%4100.00%



#ifdef CONFIG_SECCOMP_FILTER
/* Returns 1 if the parent is an ancestor of the child. */



static int is_ancestor(struct seccomp_filter *parent,
		       struct seccomp_filter *child)
{
	/* NULL is the root ancestor. */
	if (parent == NULL)
		return 1;
	for (; child; child = child->prev)
		if (child == parent)
			return 1;
	return 0;
}


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Total49100.00%1100.00%



/**
 * seccomp_can_sync_threads: checks if all threads can be synchronized
 *
 * Expects sighand and cred_guard_mutex locks to be held.
 *
 * Returns 0 on success, -ve on error, or the pid of a thread which was
 * either not in the correct seccomp mode or it did not have an ancestral
 * seccomp filter.
 */



static inline pid_t seccomp_can_sync_threads(void)
{
	struct task_struct *thread, *caller;

	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
	assert_spin_locked(&current->sighand->siglock);

	/* Validate all threads being eligible for synchronization. */
	caller = current;
	for_each_thread(caller, thread) {
		pid_t failed;

		/* Skip current, since it is initiating the sync. */
		if (thread == caller)
			continue;

		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
		    (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
		     is_ancestor(thread->seccomp.filter,
				 caller->seccomp.filter)))
			continue;

		/* Return the first thread that cannot be synchronized. */
		failed = task_pid_vnr(thread);
		/* If the pid cannot be resolved, then return -ESRCH */
		if (unlikely(WARN_ON(failed == 0)))
			failed = -ESRCH;
		return failed;
	}

	return 0;
}


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Guenter Roeck10.75%150.00%


Total133100.00%2100.00%



/**
 * seccomp_sync_threads: sets all threads to use current's filter
 *
 * Expects sighand and cred_guard_mutex locks to be held, and for
 * seccomp_can_sync_threads() to have returned success already
 * without dropping the locks.
 *
 */



static inline void seccomp_sync_threads(void)
{
	struct task_struct *thread, *caller;

	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
	assert_spin_locked(&current->sighand->siglock);

	/* Synchronize all threads. */
	caller = current;
	for_each_thread(caller, thread) {
		/* Skip current, since it needs no changes. */
		if (thread == caller)
			continue;

		/* Get a task reference for the new leaf node. */
		get_seccomp_filter(caller);
		/*
                 * Drop the task reference to the shared ancestor since
                 * current's path will hold a reference.  (This also
                 * allows a put before the assignment.)
                 */
		put_seccomp_filter(thread);
		smp_store_release(&thread->seccomp.filter,
				  caller->seccomp.filter);

		/*
                 * Don't let an unprivileged task work around
                 * the no_new_privs restriction by creating
                 * a thread that sets it up, enters seccomp,
                 * then dies.
                 */
		if (task_no_new_privs(caller))
			task_set_no_new_privs(thread);

		/*
                 * Opt the other thread into seccomp if needed.
                 * As threads are considered to be trust-realm
                 * equivalent (see ptrace_may_access), it is safe to
                 * allow one thread to transition the other.
                 */
		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
			seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
	}
}


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Jann Horn129.92%133.33%


Guenter Roeck10.83%133.33%


Total121100.00%3100.00%



/**
 * seccomp_prepare_filter: Prepares a seccomp filter for use.
 * @fprog: BPF program to install
 *
 * Returns filter on success or an ERR_PTR on failure.
 */



static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
	struct seccomp_filter *sfilter;
	int ret;
	const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE);

	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
		return ERR_PTR(-EINVAL);

	BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));

	/*
         * Installing a seccomp filter requires that the task has
         * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
         * This avoids scenarios where unprivileged tasks can affect the
         * behavior of privileged children.
         */
	if (!task_no_new_privs(current) &&
	    security_capable_noaudit(current_cred(), current_user_ns(),
				     CAP_SYS_ADMIN) != 0)
		return ERR_PTR(-EACCES);

	/* Allocate a new seccomp_filter */
	sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
	if (!sfilter)
		return ERR_PTR(-ENOMEM);

	ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
					seccomp_check_filter, save_orig);
	if (ret < 0) {
		kfree(sfilter);
		return ERR_PTR(ret);
	}

	refcount_set(&sfilter->usage, 1);

	return sfilter;
}


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Kees Cook3118.13%325.00%


Daniel Borkmann2816.37%216.67%


Alexei Starovoitov1810.53%216.67%


Nicolas Schichan116.43%18.33%


Tycho Andersen95.26%18.33%


Masahiro Yamada10.58%18.33%


Fabian Frederick10.58%18.33%


Total171100.00%12100.00%



/**
 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
 * @user_filter: pointer to the user data containing a sock_fprog.
 *
 * Returns 0 on success and non-zero otherwise.
 */


static struct seccomp_filter *

seccomp_prepare_user_filter(const char __user *user_filter)
{
	struct sock_fprog fprog;
	struct seccomp_filter *filter = ERR_PTR(-EFAULT);

#ifdef CONFIG_COMPAT
	if (in_compat_syscall()) {
		struct compat_sock_fprog fprog32;
		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
			goto out;
		fprog.len = fprog32.len;
		fprog.filter = compat_ptr(fprog32.filter);
	} else /* falls through to the if below. */
#endif
	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
		goto out;
	filter = seccomp_prepare_filter(&fprog);
out:
	return filter;
}


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Will Drewry9683.48%120.00%


Kees Cook1714.78%240.00%


Rashika Kheria10.87%120.00%


Andrew Lutomirski10.87%120.00%


Total115100.00%5100.00%



/**
 * seccomp_attach_filter: validate and attach filter
 * @flags:  flags to change filter behavior
 * @filter: seccomp filter to add to the current process
 *
 * Caller must be holding current->sighand->siglock lock.
 *
 * Returns 0 on success, -ve on error.
 */



static long seccomp_attach_filter(unsigned int flags,
				  struct seccomp_filter *filter)
{
	unsigned long total_insns;
	struct seccomp_filter *walker;

	assert_spin_locked(&current->sighand->siglock);

	/* Validate resulting filter length. */
	total_insns = filter->prog->len;
	for (walker = current->seccomp.filter; walker; walker = walker->prev)
		total_insns += walker->prog->len + 4;  /* 4 instr penalty */
	if (total_insns > MAX_INSNS_PER_PATH)
		return -ENOMEM;

	/* If thread sync has been requested, check that it is possible. */
	if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
		int ret;

		ret = seccomp_can_sync_threads();
		if (ret)
			return ret;
	}

	/* Set log flag, if present. */
	if (flags & SECCOMP_FILTER_FLAG_LOG)
		filter->log = true;

	/*
         * If there is an existing filter, make it the prev and don't drop its
         * task reference.
         */
	filter->prev = current->seccomp.filter;
	current->seccomp.filter = filter;

	/* Now that the new filter is in place, synchronize to all threads. */
	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
		seccomp_sync_threads();

	return 0;
}


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Tyler Hicks138.61%116.67%


Will Drewry21.32%116.67%


Guenter Roeck10.66%116.67%


Total151100.00%6100.00%






static void __get_seccomp_filter(struct seccomp_filter *filter)
{
	/* Reference count is bounded by the number of total processes. */
	refcount_inc(&filter->usage);
}


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Colin Ian King15.00%150.00%


Total20100.00%2100.00%



/* get_seccomp_filter - increments the reference count of the filter on @tsk */



void get_seccomp_filter(struct task_struct *tsk)
{
	struct seccomp_filter *orig = tsk->seccomp.filter;
	if (!orig)
		return;
	__get_seccomp_filter(orig);
}


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Oleg Nesterov13.12%150.00%


Total32100.00%2100.00%






static inline void seccomp_filter_free(struct seccomp_filter *filter)
{
	if (filter) {
		bpf_prog_destroy(filter->prog);
		kfree(filter);
	}
}


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Daniel Borkmann13.33%150.00%


Total30100.00%2100.00%






static void __put_seccomp_filter(struct seccomp_filter *orig)
{
	/* Clean up single-reference branches iteratively. */
	while (orig && refcount_dec_and_test(&orig->usage)) {
		struct seccomp_filter *freeme = orig;
		orig = orig->prev;
		seccomp_filter_free(freeme);
	}
}


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Oleg Nesterov49.09%125.00%


Kees Cook24.55%250.00%


Total44100.00%4100.00%



/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */



void put_seccomp_filter(struct task_struct *tsk)
{
	__put_seccomp_filter(tsk->seccomp.filter);
}


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static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
{
	memset(info, 0, sizeof(*info));
	info->si_signo = SIGSYS;
	info->si_code = SYS_SECCOMP;
	info->si_call_addr = (void __user *)KSTK_EIP(current);
	info->si_errno = reason;
	info->si_arch = syscall_get_arch();
	info->si_syscall = syscall;
}


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Mike Frysinger1317.57%133.33%


Eric Paris11.35%133.33%


Total74100.00%3100.00%



/**
 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
 * @syscall: syscall number to send to userland
 * @reason: filter-supplied reason code to send to userland (via si_errno)
 *
 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
 */



static void seccomp_send_sigsys(int syscall, int reason)
{
	struct siginfo info;
	seccomp_init_siginfo(&info, syscall, reason);
	force_sig_info(SIGSYS, &info, current);
}

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#endif	/* CONFIG_SECCOMP_FILTER */

/* For use with seccomp_actions_logged */

#define SECCOMP_LOG_KILL_PROCESS	(1 << 0)

#define SECCOMP_LOG_KILL_THREAD		(1 << 1)

#define SECCOMP_LOG_TRAP		(1 << 2)

#define SECCOMP_LOG_ERRNO		(1 << 3)

#define SECCOMP_LOG_TRACE		(1 << 4)

#define SECCOMP_LOG_LOG			(1 << 5)

#define SECCOMP_LOG_ALLOW		(1 << 6)


static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
				    SECCOMP_LOG_KILL_THREAD  |
				    SECCOMP_LOG_TRAP  |
				    SECCOMP_LOG_ERRNO |
				    SECCOMP_LOG_TRACE |
				    SECCOMP_LOG_LOG;




static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
			       bool requested)
{
	bool log = false;

	switch (action) {
	case SECCOMP_RET_ALLOW:
		break;
	case SECCOMP_RET_TRAP:
		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
		break;
	case SECCOMP_RET_ERRNO:
		log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
		break;
	case SECCOMP_RET_TRACE:
		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
		break;
	case SECCOMP_RET_LOG:
		log = seccomp_actions_logged & SECCOMP_LOG_LOG;
		break;
	case SECCOMP_RET_KILL_THREAD:
		log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
		break;
	case SECCOMP_RET_KILL_PROCESS:
	default:
		log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
	}

	/*
         * Force an audit message to be emitted when the action is RET_KILL_*,
         * RET_LOG, or the FILTER_FLAG_LOG bit was set and the action is
         * allowed to be logged by the admin.
         */
	if (log)
		return __audit_seccomp(syscall, signr, action);

	/*
         * Let the audit subsystem decide if the action should be audited based
         * on whether the current task itself is being audited.
         */
	return audit_seccomp(syscall, signr, action);
}


Contributors
PersonTokensPropCommitsCommitProp
Tyler Hicks11388.98%360.00%


Kees Cook1411.02%240.00%


Total127100.00%5100.00%



/*
 * Secure computing mode 1 allows only read/write/exit/sigreturn.
 * To be fully secure this must be combined with rlimit
 * to limit the stack allocations too.
 */

static const int mode1_syscalls[] = {
	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
	0, /* null terminated */
};




static void __secure_computing_strict(int this_syscall)
{
	const int *syscall_whitelist = mode1_syscalls;
#ifdef CONFIG_COMPAT
	if (in_compat_syscall())
		syscall_whitelist = get_compat_mode1_syscalls();
#endif
	do {
		if (*syscall_whitelist == this_syscall)
			return;
	} while (*++syscall_whitelist);

#ifdef SECCOMP_DEBUG
	dump_stack();
#endif
	seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
	do_exit(SIGKILL);
}


Contributors
PersonTokensPropCommitsCommitProp
Andrea Arcangeli3243.84%19.09%


Andrew Lutomirski3041.10%218.18%


Matt Redfearn34.11%218.18%


Tyler Hicks34.11%218.18%


Will Drewry22.74%218.18%


Roland McGrath22.74%19.09%


Kees Cook11.37%19.09%


Total73100.00%11100.00%



#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER



void secure_computing_strict(int this_syscall)
{
	int mode = current->seccomp.mode;

	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
		return;

	if (mode == SECCOMP_MODE_DISABLED)
		return;
	else if (mode == SECCOMP_MODE_STRICT)
		__secure_computing_strict(this_syscall);
	else
		BUG();
}

Contributors
PersonTokensPropCommitsCommitProp
Andrew Lutomirski3663.16%120.00%


Tycho Andersen1628.07%120.00%


Will Drewry35.26%120.00%


Masahiro Yamada11.75%120.00%


Kees Cook11.75%120.00%


Total57100.00%5100.00%



#else

#ifdef CONFIG_SECCOMP_FILTER



static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
			    const bool recheck_after_trace)
{
	u32 filter_ret, action;
	struct seccomp_filter *match = NULL;
	int data;

	/*
         * Make sure that any changes to mode from another thread have
         * been seen after TIF_SECCOMP was seen.
         */
	rmb();

	filter_ret = seccomp_run_filters(sd, &match);
	data = filter_ret & SECCOMP_RET_DATA;
	action = filter_ret & SECCOMP_RET_ACTION_FULL;

	switch (action) {
	case SECCOMP_RET_ERRNO:
		/* Set low-order bits as an errno, capped at MAX_ERRNO. */
		if (data > MAX_ERRNO)
			data = MAX_ERRNO;
		syscall_set_return_value(current, task_pt_regs(current),
					 -data, 0);
		goto skip;

	case SECCOMP_RET_TRAP:
		/* Show the handler the original registers. */
		syscall_rollback(current, task_pt_regs(current));
		/* Let the filter pass back 16 bits of data. */
		seccomp_send_sigsys(this_syscall, data);
		goto skip;

	case SECCOMP_RET_TRACE:
		/* We've been put in this state by the ptracer already. */
		if (recheck_after_trace)
			return 0;

		/* ENOSYS these calls if there is no tracer attached. */
		if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
			syscall_set_return_value(current,
						 task_pt_regs(current),
						 -ENOSYS, 0);
			goto skip;
		}

		/* Allow the BPF to provide the event message */
		ptrace_event(PTRACE_EVENT_SECCOMP, data);
		/*
                 * The delivery of a fatal signal during event
                 * notification may silently skip tracer notification,
                 * which could leave us with a potentially unmodified
                 * syscall that the tracer would have liked to have
                 * changed. Since the process is about to die, we just
                 * force the syscall to be skipped and let the signal
                 * kill the process and correctly handle any tracer exit
                 * notifications.
                 */
		if (fatal_signal_pending(current))
			goto skip;
		/* Check if the tracer forced the syscall to be skipped. */
		this_syscall = syscall_get_nr(current, task_pt_regs(current));
		if (this_syscall < 0)
			goto skip;

		/*
                 * Recheck the syscall, since it may have changed. This
                 * intentionally uses a NULL struct seccomp_data to force
                 * a reload of all registers. This does not goto skip since
                 * a skip would have already been reported.
                 */
		if (__seccomp_filter(this_syscall, NULL, true))
			return -1;

		return 0;

	case SECCOMP_RET_LOG:
		seccomp_log(this_syscall, 0, action, true);
		return 0;

	case SECCOMP_RET_ALLOW:
		/*
                 * Note that the "match" filter will always be NULL for
                 * this action since SECCOMP_RET_ALLOW is the starting
                 * state in seccomp_run_filters().
                 */
		return 0;

	case SECCOMP_RET_KILL_THREAD:
	case SECCOMP_RET_KILL_PROCESS:
	default:
		seccomp_log(this_syscall, SIGSYS, action, true);
		/* Dump core only if this is the last remaining thread. */
		if (action == SECCOMP_RET_KILL_PROCESS ||
		    get_nr_threads(current) == 1) {
			siginfo_t info;

			/* Show the original registers in the dump. */
			syscall_rollback(current, task_pt_regs(current));
			/* Trigger a manual coredump since do_exit skips it. */
			seccomp_init_siginfo(&info, this_syscall, data);
			do_coredump(&info);
		}
		if (action == SECCOMP_RET_KILL_PROCESS)
			do_group_exit(SIGSYS);
		else
			do_exit(SIGSYS);
	}

	unreachable();

skip:
	seccomp_log(this_syscall, 0, action, match ? match->log : false);
	return -1;
}

Contributors
PersonTokensPropCommitsCommitProp
Kees Cook16546.22%1045.45%


Andrew Lutomirski7922.13%313.64%


Will Drewry5615.69%522.73%


Tyler Hicks298.12%313.64%


Mike Frysinger287.84%14.55%


Total357100.00%22100.00%



#else



static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
			    const bool recheck_after_trace)
{
	BUG();
}

Contributors
PersonTokensPropCommitsCommitProp
Kees Cook22100.00%2100.00%


Total22100.00%2100.00%



#endif




int __secure_computing(const struct seccomp_data *sd)
{
	int mode = current->seccomp.mode;
	int this_syscall;

	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
		return 0;

	this_syscall = sd ? sd->nr :
		syscall_get_nr(current, task_pt_regs(current));

	switch (mode) {
	case SECCOMP_MODE_STRICT:
		__secure_computing_strict(this_syscall);  /* may call do_exit */
		return 0;
	case SECCOMP_MODE_FILTER:
		return __seccomp_filter(this_syscall, sd, false);
	default:
		BUG();
	}
}

Contributors
PersonTokensPropCommitsCommitProp
Andrew Lutomirski5153.68%233.33%


Kees Cook2627.37%233.33%


Tycho Andersen1717.89%116.67%


Masahiro Yamada11.05%116.67%


Total95100.00%6100.00%



#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */




long prctl_get_seccomp(void)
{
	return current->seccomp.mode;
}


Contributors
PersonTokensPropCommitsCommitProp
Andrea Arcangeli14100.00%1100.00%


Total14100.00%1100.00%



/**
 * seccomp_set_mode_strict: internal function for setting strict seccomp
 *
 * Once current->seccomp.mode is non-zero, it may not be changed.
 *
 * Returns 0 on success or -EINVAL on failure.
 */



static long seccomp_set_mode_strict(void)
{
	const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
	long ret = -EINVAL;

	spin_lock_irq(&current->sighand->siglock);

	if (!seccomp_may_assign_mode(seccomp_mode))
		goto out;

#ifdef TIF_NOTSC
	disable_TSC();
#endif
	seccomp_assign_mode(