1 // SPDX-License-Identifier: GPL-2.0
3 * linux/kernel/seccomp.c
5 * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
7 * Copyright (C) 2012 Google, Inc.
8 * Will Drewry <wad@chromium.org>
10 * This defines a simple but solid secure-computing facility.
12 * Mode 1 uses a fixed list of allowed system calls.
13 * Mode 2 allows user-defined system call filters in the form
14 * of Berkeley Packet Filters/Linux Socket Filters.
17 #include <linux/refcount.h>
18 #include <linux/audit.h>
19 #include <linux/compat.h>
20 #include <linux/coredump.h>
21 #include <linux/kmemleak.h>
22 #include <linux/nospec.h>
23 #include <linux/prctl.h>
24 #include <linux/sched.h>
25 #include <linux/sched/task_stack.h>
26 #include <linux/seccomp.h>
27 #include <linux/slab.h>
28 #include <linux/syscalls.h>
29 #include <linux/sysctl.h>
31 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
32 #include <asm/syscall.h>
35 #ifdef CONFIG_SECCOMP_FILTER
36 #include <linux/filter.h>
37 #include <linux/pid.h>
38 #include <linux/ptrace.h>
39 #include <linux/security.h>
40 #include <linux/tracehook.h>
41 #include <linux/uaccess.h>
44 * struct seccomp_filter - container for seccomp BPF programs
46 * @usage: reference count to manage the object lifetime.
47 * get/put helpers should be used when accessing an instance
48 * outside of a lifetime-guarded section. In general, this
49 * is only needed for handling filters shared across tasks.
50 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
51 * @prev: points to a previously installed, or inherited, filter
52 * @prog: the BPF program to evaluate
54 * seccomp_filter objects are organized in a tree linked via the @prev
55 * pointer. For any task, it appears to be a singly-linked list starting
56 * with current->seccomp.filter, the most recently attached or inherited filter.
57 * However, multiple filters may share a @prev node, by way of fork(), which
58 * results in a unidirectional tree existing in memory. This is similar to
59 * how namespaces work.
61 * seccomp_filter objects should never be modified after being attached
62 * to a task_struct (other than @usage).
64 struct seccomp_filter {
67 struct seccomp_filter *prev;
68 struct bpf_prog *prog;
71 /* Limit any path through the tree to 256KB worth of instructions. */
72 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
75 * Endianness is explicitly ignored and left for BPF program authors to manage
76 * as per the specific architecture.
78 static void populate_seccomp_data(struct seccomp_data *sd)
80 struct task_struct *task = current;
81 struct pt_regs *regs = task_pt_regs(task);
82 unsigned long args[6];
84 sd->nr = syscall_get_nr(task, regs);
85 sd->arch = syscall_get_arch();
86 syscall_get_arguments(task, regs, 0, 6, args);
87 sd->args[0] = args[0];
88 sd->args[1] = args[1];
89 sd->args[2] = args[2];
90 sd->args[3] = args[3];
91 sd->args[4] = args[4];
92 sd->args[5] = args[5];
93 sd->instruction_pointer = KSTK_EIP(task);
97 * seccomp_check_filter - verify seccomp filter code
98 * @filter: filter to verify
99 * @flen: length of filter
101 * Takes a previously checked filter (by bpf_check_classic) and
102 * redirects all filter code that loads struct sk_buff data
103 * and related data through seccomp_bpf_load. It also
104 * enforces length and alignment checking of those loads.
106 * Returns 0 if the rule set is legal or -EINVAL if not.
108 static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
111 for (pc = 0; pc < flen; pc++) {
112 struct sock_filter *ftest = &filter[pc];
113 u16 code = ftest->code;
117 case BPF_LD | BPF_W | BPF_ABS:
118 ftest->code = BPF_LDX | BPF_W | BPF_ABS;
119 /* 32-bit aligned and not out of bounds. */
120 if (k >= sizeof(struct seccomp_data) || k & 3)
123 case BPF_LD | BPF_W | BPF_LEN:
124 ftest->code = BPF_LD | BPF_IMM;
125 ftest->k = sizeof(struct seccomp_data);
127 case BPF_LDX | BPF_W | BPF_LEN:
128 ftest->code = BPF_LDX | BPF_IMM;
129 ftest->k = sizeof(struct seccomp_data);
131 /* Explicitly include allowed calls. */
132 case BPF_RET | BPF_K:
133 case BPF_RET | BPF_A:
134 case BPF_ALU | BPF_ADD | BPF_K:
135 case BPF_ALU | BPF_ADD | BPF_X:
136 case BPF_ALU | BPF_SUB | BPF_K:
137 case BPF_ALU | BPF_SUB | BPF_X:
138 case BPF_ALU | BPF_MUL | BPF_K:
139 case BPF_ALU | BPF_MUL | BPF_X:
140 case BPF_ALU | BPF_DIV | BPF_K:
141 case BPF_ALU | BPF_DIV | BPF_X:
142 case BPF_ALU | BPF_AND | BPF_K:
143 case BPF_ALU | BPF_AND | BPF_X:
144 case BPF_ALU | BPF_OR | BPF_K:
145 case BPF_ALU | BPF_OR | BPF_X:
146 case BPF_ALU | BPF_XOR | BPF_K:
147 case BPF_ALU | BPF_XOR | BPF_X:
148 case BPF_ALU | BPF_LSH | BPF_K:
149 case BPF_ALU | BPF_LSH | BPF_X:
150 case BPF_ALU | BPF_RSH | BPF_K:
151 case BPF_ALU | BPF_RSH | BPF_X:
152 case BPF_ALU | BPF_NEG:
153 case BPF_LD | BPF_IMM:
154 case BPF_LDX | BPF_IMM:
155 case BPF_MISC | BPF_TAX:
156 case BPF_MISC | BPF_TXA:
157 case BPF_LD | BPF_MEM:
158 case BPF_LDX | BPF_MEM:
161 case BPF_JMP | BPF_JA:
162 case BPF_JMP | BPF_JEQ | BPF_K:
163 case BPF_JMP | BPF_JEQ | BPF_X:
164 case BPF_JMP | BPF_JGE | BPF_K:
165 case BPF_JMP | BPF_JGE | BPF_X:
166 case BPF_JMP | BPF_JGT | BPF_K:
167 case BPF_JMP | BPF_JGT | BPF_X:
168 case BPF_JMP | BPF_JSET | BPF_K:
169 case BPF_JMP | BPF_JSET | BPF_X:
179 * seccomp_run_filters - evaluates all seccomp filters against @sd
180 * @sd: optional seccomp data to be passed to filters
181 * @match: stores struct seccomp_filter that resulted in the return value,
182 * unless filter returned SECCOMP_RET_ALLOW, in which case it will
185 * Returns valid seccomp BPF response codes.
187 #define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
188 static u32 seccomp_run_filters(const struct seccomp_data *sd,
189 struct seccomp_filter **match)
191 struct seccomp_data sd_local;
192 u32 ret = SECCOMP_RET_ALLOW;
193 /* Make sure cross-thread synced filter points somewhere sane. */
194 struct seccomp_filter *f =
195 READ_ONCE(current->seccomp.filter);
197 /* Ensure unexpected behavior doesn't result in failing open. */
198 if (unlikely(WARN_ON(f == NULL)))
199 return SECCOMP_RET_KILL_PROCESS;
202 populate_seccomp_data(&sd_local);
207 * All filters in the list are evaluated and the lowest BPF return
208 * value always takes priority (ignoring the DATA).
210 for (; f; f = f->prev) {
211 u32 cur_ret = BPF_PROG_RUN(f->prog, sd);
213 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
220 #endif /* CONFIG_SECCOMP_FILTER */
222 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
224 assert_spin_locked(¤t->sighand->siglock);
226 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
232 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
234 static inline void seccomp_assign_mode(struct task_struct *task,
235 unsigned long seccomp_mode,
238 assert_spin_locked(&task->sighand->siglock);
240 task->seccomp.mode = seccomp_mode;
242 * Make sure TIF_SECCOMP cannot be set before the mode (and
245 smp_mb__before_atomic();
246 /* Assume default seccomp processes want spec flaw mitigation. */
247 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
248 arch_seccomp_spec_mitigate(task);
249 set_tsk_thread_flag(task, TIF_SECCOMP);
252 #ifdef CONFIG_SECCOMP_FILTER
253 /* Returns 1 if the parent is an ancestor of the child. */
254 static int is_ancestor(struct seccomp_filter *parent,
255 struct seccomp_filter *child)
257 /* NULL is the root ancestor. */
260 for (; child; child = child->prev)
267 * seccomp_can_sync_threads: checks if all threads can be synchronized
269 * Expects sighand and cred_guard_mutex locks to be held.
271 * Returns 0 on success, -ve on error, or the pid of a thread which was
272 * either not in the correct seccomp mode or it did not have an ancestral
275 static inline pid_t seccomp_can_sync_threads(void)
277 struct task_struct *thread, *caller;
279 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
280 assert_spin_locked(¤t->sighand->siglock);
282 /* Validate all threads being eligible for synchronization. */
284 for_each_thread(caller, thread) {
287 /* Skip current, since it is initiating the sync. */
288 if (thread == caller)
291 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
292 (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
293 is_ancestor(thread->seccomp.filter,
294 caller->seccomp.filter)))
297 /* Return the first thread that cannot be synchronized. */
298 failed = task_pid_vnr(thread);
299 /* If the pid cannot be resolved, then return -ESRCH */
300 if (unlikely(WARN_ON(failed == 0)))
309 * seccomp_sync_threads: sets all threads to use current's filter
311 * Expects sighand and cred_guard_mutex locks to be held, and for
312 * seccomp_can_sync_threads() to have returned success already
313 * without dropping the locks.
316 static inline void seccomp_sync_threads(unsigned long flags)
318 struct task_struct *thread, *caller;
320 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
321 assert_spin_locked(¤t->sighand->siglock);
323 /* Synchronize all threads. */
325 for_each_thread(caller, thread) {
326 /* Skip current, since it needs no changes. */
327 if (thread == caller)
330 /* Get a task reference for the new leaf node. */
331 get_seccomp_filter(caller);
333 * Drop the task reference to the shared ancestor since
334 * current's path will hold a reference. (This also
335 * allows a put before the assignment.)
337 put_seccomp_filter(thread);
338 smp_store_release(&thread->seccomp.filter,
339 caller->seccomp.filter);
342 * Don't let an unprivileged task work around
343 * the no_new_privs restriction by creating
344 * a thread that sets it up, enters seccomp,
347 if (task_no_new_privs(caller))
348 task_set_no_new_privs(thread);
351 * Opt the other thread into seccomp if needed.
352 * As threads are considered to be trust-realm
353 * equivalent (see ptrace_may_access), it is safe to
354 * allow one thread to transition the other.
356 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
357 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
363 * seccomp_prepare_filter: Prepares a seccomp filter for use.
364 * @fprog: BPF program to install
366 * Returns filter on success or an ERR_PTR on failure.
368 static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
370 struct seccomp_filter *sfilter;
372 const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE);
374 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
375 return ERR_PTR(-EINVAL);
377 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
380 * Installing a seccomp filter requires that the task has
381 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
382 * This avoids scenarios where unprivileged tasks can affect the
383 * behavior of privileged children.
385 if (!task_no_new_privs(current) &&
386 security_capable_noaudit(current_cred(), current_user_ns(),
388 return ERR_PTR(-EACCES);
390 /* Allocate a new seccomp_filter */
391 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
393 return ERR_PTR(-ENOMEM);
395 ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
396 seccomp_check_filter, save_orig);
402 refcount_set(&sfilter->usage, 1);
408 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
409 * @user_filter: pointer to the user data containing a sock_fprog.
411 * Returns 0 on success and non-zero otherwise.
413 static struct seccomp_filter *
414 seccomp_prepare_user_filter(const char __user *user_filter)
416 struct sock_fprog fprog;
417 struct seccomp_filter *filter = ERR_PTR(-EFAULT);
420 if (in_compat_syscall()) {
421 struct compat_sock_fprog fprog32;
422 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
424 fprog.len = fprog32.len;
425 fprog.filter = compat_ptr(fprog32.filter);
426 } else /* falls through to the if below. */
428 if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
430 filter = seccomp_prepare_filter(&fprog);
436 * seccomp_attach_filter: validate and attach filter
437 * @flags: flags to change filter behavior
438 * @filter: seccomp filter to add to the current process
440 * Caller must be holding current->sighand->siglock lock.
442 * Returns 0 on success, -ve on error.
444 static long seccomp_attach_filter(unsigned int flags,
445 struct seccomp_filter *filter)
447 unsigned long total_insns;
448 struct seccomp_filter *walker;
450 assert_spin_locked(¤t->sighand->siglock);
452 /* Validate resulting filter length. */
453 total_insns = filter->prog->len;
454 for (walker = current->seccomp.filter; walker; walker = walker->prev)
455 total_insns += walker->prog->len + 4; /* 4 instr penalty */
456 if (total_insns > MAX_INSNS_PER_PATH)
459 /* If thread sync has been requested, check that it is possible. */
460 if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
463 ret = seccomp_can_sync_threads();
468 /* Set log flag, if present. */
469 if (flags & SECCOMP_FILTER_FLAG_LOG)
473 * If there is an existing filter, make it the prev and don't drop its
476 filter->prev = current->seccomp.filter;
477 current->seccomp.filter = filter;
479 /* Now that the new filter is in place, synchronize to all threads. */
480 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
481 seccomp_sync_threads(flags);
486 static void __get_seccomp_filter(struct seccomp_filter *filter)
488 /* Reference count is bounded by the number of total processes. */
489 refcount_inc(&filter->usage);
492 /* get_seccomp_filter - increments the reference count of the filter on @tsk */
493 void get_seccomp_filter(struct task_struct *tsk)
495 struct seccomp_filter *orig = tsk->seccomp.filter;
498 __get_seccomp_filter(orig);
501 static inline void seccomp_filter_free(struct seccomp_filter *filter)
504 bpf_prog_destroy(filter->prog);
509 static void __put_seccomp_filter(struct seccomp_filter *orig)
511 /* Clean up single-reference branches iteratively. */
512 while (orig && refcount_dec_and_test(&orig->usage)) {
513 struct seccomp_filter *freeme = orig;
515 seccomp_filter_free(freeme);
519 /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
520 void put_seccomp_filter(struct task_struct *tsk)
522 __put_seccomp_filter(tsk->seccomp.filter);
525 static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
528 info->si_signo = SIGSYS;
529 info->si_code = SYS_SECCOMP;
530 info->si_call_addr = (void __user *)KSTK_EIP(current);
531 info->si_errno = reason;
532 info->si_arch = syscall_get_arch();
533 info->si_syscall = syscall;
537 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
538 * @syscall: syscall number to send to userland
539 * @reason: filter-supplied reason code to send to userland (via si_errno)
541 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
543 static void seccomp_send_sigsys(int syscall, int reason)
546 seccomp_init_siginfo(&info, syscall, reason);
547 force_sig_info(SIGSYS, &info, current);
549 #endif /* CONFIG_SECCOMP_FILTER */
551 /* For use with seccomp_actions_logged */
552 #define SECCOMP_LOG_KILL_PROCESS (1 << 0)
553 #define SECCOMP_LOG_KILL_THREAD (1 << 1)
554 #define SECCOMP_LOG_TRAP (1 << 2)
555 #define SECCOMP_LOG_ERRNO (1 << 3)
556 #define SECCOMP_LOG_TRACE (1 << 4)
557 #define SECCOMP_LOG_LOG (1 << 5)
558 #define SECCOMP_LOG_ALLOW (1 << 6)
560 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
561 SECCOMP_LOG_KILL_THREAD |
567 static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
573 case SECCOMP_RET_ALLOW:
575 case SECCOMP_RET_TRAP:
576 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
578 case SECCOMP_RET_ERRNO:
579 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
581 case SECCOMP_RET_TRACE:
582 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
584 case SECCOMP_RET_LOG:
585 log = seccomp_actions_logged & SECCOMP_LOG_LOG;
587 case SECCOMP_RET_KILL_THREAD:
588 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
590 case SECCOMP_RET_KILL_PROCESS:
592 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
596 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
597 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
598 * any action from being logged by removing the action name from the
599 * seccomp_actions_logged sysctl.
604 audit_seccomp(syscall, signr, action);
608 * Secure computing mode 1 allows only read/write/exit/sigreturn.
609 * To be fully secure this must be combined with rlimit
610 * to limit the stack allocations too.
612 static const int mode1_syscalls[] = {
613 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
614 0, /* null terminated */
617 static void __secure_computing_strict(int this_syscall)
619 const int *syscall_whitelist = mode1_syscalls;
621 if (in_compat_syscall())
622 syscall_whitelist = get_compat_mode1_syscalls();
625 if (*syscall_whitelist == this_syscall)
627 } while (*++syscall_whitelist);
632 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
636 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
637 void secure_computing_strict(int this_syscall)
639 int mode = current->seccomp.mode;
641 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
642 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
645 if (mode == SECCOMP_MODE_DISABLED)
647 else if (mode == SECCOMP_MODE_STRICT)
648 __secure_computing_strict(this_syscall);
654 #ifdef CONFIG_SECCOMP_FILTER
655 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
656 const bool recheck_after_trace)
658 u32 filter_ret, action;
659 struct seccomp_filter *match = NULL;
663 * Make sure that any changes to mode from another thread have
664 * been seen after TIF_SECCOMP was seen.
668 filter_ret = seccomp_run_filters(sd, &match);
669 data = filter_ret & SECCOMP_RET_DATA;
670 action = filter_ret & SECCOMP_RET_ACTION_FULL;
673 case SECCOMP_RET_ERRNO:
674 /* Set low-order bits as an errno, capped at MAX_ERRNO. */
675 if (data > MAX_ERRNO)
677 syscall_set_return_value(current, task_pt_regs(current),
681 case SECCOMP_RET_TRAP:
682 /* Show the handler the original registers. */
683 syscall_rollback(current, task_pt_regs(current));
684 /* Let the filter pass back 16 bits of data. */
685 seccomp_send_sigsys(this_syscall, data);
688 case SECCOMP_RET_TRACE:
689 /* We've been put in this state by the ptracer already. */
690 if (recheck_after_trace)
693 /* ENOSYS these calls if there is no tracer attached. */
694 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
695 syscall_set_return_value(current,
696 task_pt_regs(current),
701 /* Allow the BPF to provide the event message */
702 ptrace_event(PTRACE_EVENT_SECCOMP, data);
704 * The delivery of a fatal signal during event
705 * notification may silently skip tracer notification,
706 * which could leave us with a potentially unmodified
707 * syscall that the tracer would have liked to have
708 * changed. Since the process is about to die, we just
709 * force the syscall to be skipped and let the signal
710 * kill the process and correctly handle any tracer exit
713 if (fatal_signal_pending(current))
715 /* Check if the tracer forced the syscall to be skipped. */
716 this_syscall = syscall_get_nr(current, task_pt_regs(current));
717 if (this_syscall < 0)
721 * Recheck the syscall, since it may have changed. This
722 * intentionally uses a NULL struct seccomp_data to force
723 * a reload of all registers. This does not goto skip since
724 * a skip would have already been reported.
726 if (__seccomp_filter(this_syscall, NULL, true))
731 case SECCOMP_RET_LOG:
732 seccomp_log(this_syscall, 0, action, true);
735 case SECCOMP_RET_ALLOW:
737 * Note that the "match" filter will always be NULL for
738 * this action since SECCOMP_RET_ALLOW is the starting
739 * state in seccomp_run_filters().
743 case SECCOMP_RET_KILL_THREAD:
744 case SECCOMP_RET_KILL_PROCESS:
746 seccomp_log(this_syscall, SIGSYS, action, true);
747 /* Dump core only if this is the last remaining thread. */
748 if (action == SECCOMP_RET_KILL_PROCESS ||
749 get_nr_threads(current) == 1) {
752 /* Show the original registers in the dump. */
753 syscall_rollback(current, task_pt_regs(current));
754 /* Trigger a manual coredump since do_exit skips it. */
755 seccomp_init_siginfo(&info, this_syscall, data);
758 if (action == SECCOMP_RET_KILL_PROCESS)
759 do_group_exit(SIGSYS);
767 seccomp_log(this_syscall, 0, action, match ? match->log : false);
771 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
772 const bool recheck_after_trace)
778 int __secure_computing(const struct seccomp_data *sd)
780 int mode = current->seccomp.mode;
783 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
784 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
787 this_syscall = sd ? sd->nr :
788 syscall_get_nr(current, task_pt_regs(current));
791 case SECCOMP_MODE_STRICT:
792 __secure_computing_strict(this_syscall); /* may call do_exit */
794 case SECCOMP_MODE_FILTER:
795 return __seccomp_filter(this_syscall, sd, false);
800 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
802 long prctl_get_seccomp(void)
804 return current->seccomp.mode;
808 * seccomp_set_mode_strict: internal function for setting strict seccomp
810 * Once current->seccomp.mode is non-zero, it may not be changed.
812 * Returns 0 on success or -EINVAL on failure.
814 static long seccomp_set_mode_strict(void)
816 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
819 spin_lock_irq(¤t->sighand->siglock);
821 if (!seccomp_may_assign_mode(seccomp_mode))
827 seccomp_assign_mode(current, seccomp_mode, 0);
831 spin_unlock_irq(¤t->sighand->siglock);
836 #ifdef CONFIG_SECCOMP_FILTER
838 * seccomp_set_mode_filter: internal function for setting seccomp filter
839 * @flags: flags to change filter behavior
840 * @filter: struct sock_fprog containing filter
842 * This function may be called repeatedly to install additional filters.
843 * Every filter successfully installed will be evaluated (in reverse order)
844 * for each system call the task makes.
846 * Once current->seccomp.mode is non-zero, it may not be changed.
848 * Returns 0 on success or -EINVAL on failure.
850 static long seccomp_set_mode_filter(unsigned int flags,
851 const char __user *filter)
853 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
854 struct seccomp_filter *prepared = NULL;
857 /* Validate flags. */
858 if (flags & ~SECCOMP_FILTER_FLAG_MASK)
861 /* Prepare the new filter before holding any locks. */
862 prepared = seccomp_prepare_user_filter(filter);
863 if (IS_ERR(prepared))
864 return PTR_ERR(prepared);
867 * Make sure we cannot change seccomp or nnp state via TSYNC
868 * while another thread is in the middle of calling exec.
870 if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
871 mutex_lock_killable(¤t->signal->cred_guard_mutex))
874 spin_lock_irq(¤t->sighand->siglock);
876 if (!seccomp_may_assign_mode(seccomp_mode))
879 ret = seccomp_attach_filter(flags, prepared);
882 /* Do not free the successfully attached filter. */
885 seccomp_assign_mode(current, seccomp_mode, flags);
887 spin_unlock_irq(¤t->sighand->siglock);
888 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
889 mutex_unlock(¤t->signal->cred_guard_mutex);
891 seccomp_filter_free(prepared);
895 static inline long seccomp_set_mode_filter(unsigned int flags,
896 const char __user *filter)
902 static long seccomp_get_action_avail(const char __user *uaction)
906 if (copy_from_user(&action, uaction, sizeof(action)))
910 case SECCOMP_RET_KILL_PROCESS:
911 case SECCOMP_RET_KILL_THREAD:
912 case SECCOMP_RET_TRAP:
913 case SECCOMP_RET_ERRNO:
914 case SECCOMP_RET_TRACE:
915 case SECCOMP_RET_LOG:
916 case SECCOMP_RET_ALLOW:
925 /* Common entry point for both prctl and syscall. */
926 static long do_seccomp(unsigned int op, unsigned int flags,
927 const char __user *uargs)
930 case SECCOMP_SET_MODE_STRICT:
931 if (flags != 0 || uargs != NULL)
933 return seccomp_set_mode_strict();
934 case SECCOMP_SET_MODE_FILTER:
935 return seccomp_set_mode_filter(flags, uargs);
936 case SECCOMP_GET_ACTION_AVAIL:
940 return seccomp_get_action_avail(uargs);
946 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
947 const char __user *, uargs)
949 return do_seccomp(op, flags, uargs);
953 * prctl_set_seccomp: configures current->seccomp.mode
954 * @seccomp_mode: requested mode to use
955 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
957 * Returns 0 on success or -EINVAL on failure.
959 long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
964 switch (seccomp_mode) {
965 case SECCOMP_MODE_STRICT:
966 op = SECCOMP_SET_MODE_STRICT;
968 * Setting strict mode through prctl always ignored filter,
969 * so make sure it is always NULL here to pass the internal
970 * check in do_seccomp().
974 case SECCOMP_MODE_FILTER:
975 op = SECCOMP_SET_MODE_FILTER;
982 /* prctl interface doesn't have flags, so they are always zero. */
983 return do_seccomp(op, 0, uargs);
986 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
987 static struct seccomp_filter *get_nth_filter(struct task_struct *task,
988 unsigned long filter_off)
990 struct seccomp_filter *orig, *filter;
994 * Note: this is only correct because the caller should be the (ptrace)
995 * tracer of the task, otherwise lock_task_sighand is needed.
997 spin_lock_irq(&task->sighand->siglock);
999 if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
1000 spin_unlock_irq(&task->sighand->siglock);
1001 return ERR_PTR(-EINVAL);
1004 orig = task->seccomp.filter;
1005 __get_seccomp_filter(orig);
1006 spin_unlock_irq(&task->sighand->siglock);
1009 for (filter = orig; filter; filter = filter->prev)
1012 if (filter_off >= count) {
1013 filter = ERR_PTR(-ENOENT);
1017 count -= filter_off;
1018 for (filter = orig; filter && count > 1; filter = filter->prev)
1021 if (WARN_ON(count != 1 || !filter)) {
1022 filter = ERR_PTR(-ENOENT);
1026 __get_seccomp_filter(filter);
1029 __put_seccomp_filter(orig);
1033 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
1036 struct seccomp_filter *filter;
1037 struct sock_fprog_kern *fprog;
1040 if (!capable(CAP_SYS_ADMIN) ||
1041 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1045 filter = get_nth_filter(task, filter_off);
1047 return PTR_ERR(filter);
1049 fprog = filter->prog->orig_prog;
1051 /* This must be a new non-cBPF filter, since we save
1052 * every cBPF filter's orig_prog above when
1053 * CONFIG_CHECKPOINT_RESTORE is enabled.
1063 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
1067 __put_seccomp_filter(filter);
1071 long seccomp_get_metadata(struct task_struct *task,
1072 unsigned long size, void __user *data)
1075 struct seccomp_filter *filter;
1076 struct seccomp_metadata kmd = {};
1078 if (!capable(CAP_SYS_ADMIN) ||
1079 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1083 size = min_t(unsigned long, size, sizeof(kmd));
1085 if (size < sizeof(kmd.filter_off))
1088 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
1091 filter = get_nth_filter(task, kmd.filter_off);
1093 return PTR_ERR(filter);
1096 kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
1099 if (copy_to_user(data, &kmd, size))
1102 __put_seccomp_filter(filter);
1107 #ifdef CONFIG_SYSCTL
1109 /* Human readable action names for friendly sysctl interaction */
1110 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
1111 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
1112 #define SECCOMP_RET_TRAP_NAME "trap"
1113 #define SECCOMP_RET_ERRNO_NAME "errno"
1114 #define SECCOMP_RET_TRACE_NAME "trace"
1115 #define SECCOMP_RET_LOG_NAME "log"
1116 #define SECCOMP_RET_ALLOW_NAME "allow"
1118 static const char seccomp_actions_avail[] =
1119 SECCOMP_RET_KILL_PROCESS_NAME " "
1120 SECCOMP_RET_KILL_THREAD_NAME " "
1121 SECCOMP_RET_TRAP_NAME " "
1122 SECCOMP_RET_ERRNO_NAME " "
1123 SECCOMP_RET_TRACE_NAME " "
1124 SECCOMP_RET_LOG_NAME " "
1125 SECCOMP_RET_ALLOW_NAME;
1127 struct seccomp_log_name {
1132 static const struct seccomp_log_name seccomp_log_names[] = {
1133 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
1134 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
1135 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
1136 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
1137 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
1138 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
1139 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
1143 static bool seccomp_names_from_actions_logged(char *names, size_t size,
1147 const struct seccomp_log_name *cur;
1148 bool append_sep = false;
1150 for (cur = seccomp_log_names; cur->name && size; cur++) {
1153 if (!(actions_logged & cur->log))
1157 ret = strscpy(names, sep, size);
1166 ret = strscpy(names, cur->name, size);
1177 static bool seccomp_action_logged_from_name(u32 *action_logged,
1180 const struct seccomp_log_name *cur;
1182 for (cur = seccomp_log_names; cur->name; cur++) {
1183 if (!strcmp(cur->name, name)) {
1184 *action_logged = cur->log;
1192 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
1196 *actions_logged = 0;
1197 while ((name = strsep(&names, " ")) && *name) {
1198 u32 action_logged = 0;
1200 if (!seccomp_action_logged_from_name(&action_logged, name))
1203 *actions_logged |= action_logged;
1209 static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
1210 size_t *lenp, loff_t *ppos)
1212 char names[sizeof(seccomp_actions_avail)];
1213 struct ctl_table table;
1215 memset(names, 0, sizeof(names));
1217 if (!seccomp_names_from_actions_logged(names, sizeof(names),
1218 seccomp_actions_logged, " "))
1223 table.maxlen = sizeof(names);
1224 return proc_dostring(&table, 0, buffer, lenp, ppos);
1227 static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
1228 size_t *lenp, loff_t *ppos, u32 *actions_logged)
1230 char names[sizeof(seccomp_actions_avail)];
1231 struct ctl_table table;
1234 if (!capable(CAP_SYS_ADMIN))
1237 memset(names, 0, sizeof(names));
1241 table.maxlen = sizeof(names);
1242 ret = proc_dostring(&table, 1, buffer, lenp, ppos);
1246 if (!seccomp_actions_logged_from_names(actions_logged, table.data))
1249 if (*actions_logged & SECCOMP_LOG_ALLOW)
1252 seccomp_actions_logged = *actions_logged;
1256 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
1259 char names[sizeof(seccomp_actions_avail)];
1260 char old_names[sizeof(seccomp_actions_avail)];
1261 const char *new = names;
1262 const char *old = old_names;
1267 memset(names, 0, sizeof(names));
1268 memset(old_names, 0, sizeof(old_names));
1272 else if (!actions_logged)
1274 else if (!seccomp_names_from_actions_logged(names, sizeof(names),
1275 actions_logged, ","))
1278 if (!old_actions_logged)
1280 else if (!seccomp_names_from_actions_logged(old_names,
1282 old_actions_logged, ","))
1285 return audit_seccomp_actions_logged(new, old, !ret);
1288 static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
1289 void __user *buffer, size_t *lenp,
1295 u32 actions_logged = 0;
1296 u32 old_actions_logged = seccomp_actions_logged;
1298 ret = write_actions_logged(ro_table, buffer, lenp, ppos,
1300 audit_actions_logged(actions_logged, old_actions_logged, ret);
1302 ret = read_actions_logged(ro_table, buffer, lenp, ppos);
1307 static struct ctl_path seccomp_sysctl_path[] = {
1308 { .procname = "kernel", },
1309 { .procname = "seccomp", },
1313 static struct ctl_table seccomp_sysctl_table[] = {
1315 .procname = "actions_avail",
1316 .data = (void *) &seccomp_actions_avail,
1317 .maxlen = sizeof(seccomp_actions_avail),
1319 .proc_handler = proc_dostring,
1322 .procname = "actions_logged",
1324 .proc_handler = seccomp_actions_logged_handler,
1329 static int __init seccomp_sysctl_init(void)
1331 struct ctl_table_header *hdr;
1333 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
1335 pr_warn("seccomp: sysctl registration failed\n");
1337 kmemleak_not_leak(hdr);
1342 device_initcall(seccomp_sysctl_init)
1344 #endif /* CONFIG_SYSCTL */