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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/kernel/seccomp.c
4 *
5 * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
6 *
7 * Copyright (C) 2012 Google, Inc.
8 * Will Drewry <wad@chromium.org>
9 *
10 * This defines a simple but solid secure-computing facility.
11 *
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.
15 */
16
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>
30
31#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
32#include <asm/syscall.h>
33#endif
34
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>
42
43/**
44 * struct seccomp_filter - container for seccomp BPF programs
45 *
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
53 *
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.
60 *
61 * seccomp_filter objects should never be modified after being attached
62 * to a task_struct (other than @usage).
63 */
64struct seccomp_filter {
65 refcount_t usage;
66 bool log;
67 struct seccomp_filter *prev;
68 struct bpf_prog *prog;
69};
70
71/* Limit any path through the tree to 256KB worth of instructions. */
72#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
73
74/*
75 * Endianness is explicitly ignored and left for BPF program authors to manage
76 * as per the specific architecture.
77 */
78static void populate_seccomp_data(struct seccomp_data *sd)
79{
80 struct task_struct *task = current;
81 struct pt_regs *regs = task_pt_regs(task);
82 unsigned long args[6];
83
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);
94}
95
96/**
97 * seccomp_check_filter - verify seccomp filter code
98 * @filter: filter to verify
99 * @flen: length of filter
100 *
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.
105 *
106 * Returns 0 if the rule set is legal or -EINVAL if not.
107 */
108static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
109{
110 int pc;
111 for (pc = 0; pc < flen; pc++) {
112 struct sock_filter *ftest = &filter[pc];
113 u16 code = ftest->code;
114 u32 k = ftest->k;
115
116 switch (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)
121 return -EINVAL;
122 continue;
123 case BPF_LD | BPF_W | BPF_LEN:
124 ftest->code = BPF_LD | BPF_IMM;
125 ftest->k = sizeof(struct seccomp_data);
126 continue;
127 case BPF_LDX | BPF_W | BPF_LEN:
128 ftest->code = BPF_LDX | BPF_IMM;
129 ftest->k = sizeof(struct seccomp_data);
130 continue;
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:
159 case BPF_ST:
160 case BPF_STX:
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:
170 continue;
171 default:
172 return -EINVAL;
173 }
174 }
175 return 0;
176}
177
178/**
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
183 * be unchanged.
184 *
185 * Returns valid seccomp BPF response codes.
186 */
187#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
188static u32 seccomp_run_filters(const struct seccomp_data *sd,
189 struct seccomp_filter **match)
190{
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);
196
197 /* Ensure unexpected behavior doesn't result in failing open. */
198 if (unlikely(WARN_ON(f == NULL)))
199 return SECCOMP_RET_KILL_PROCESS;
200
201 if (!sd) {
202 populate_seccomp_data(&sd_local);
203 sd = &sd_local;
204 }
205
206 /*
207 * All filters in the list are evaluated and the lowest BPF return
208 * value always takes priority (ignoring the DATA).
209 */
210 for (; f; f = f->prev) {
211 u32 cur_ret = BPF_PROG_RUN(f->prog, sd);
212
213 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
214 ret = cur_ret;
215 *match = f;
216 }
217 }
218 return ret;
219}
220#endif /* CONFIG_SECCOMP_FILTER */
221
222static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
223{
224 assert_spin_locked(¤t->sighand->siglock);
225
226 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
227 return false;
228
229 return true;
230}
231
232void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
233
234static inline void seccomp_assign_mode(struct task_struct *task,
235 unsigned long seccomp_mode,
236 unsigned long flags)
237{
238 assert_spin_locked(&task->sighand->siglock);
239
240 task->seccomp.mode = seccomp_mode;
241 /*
242 * Make sure TIF_SECCOMP cannot be set before the mode (and
243 * filter) is set.
244 */
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);
250}
251
252#ifdef CONFIG_SECCOMP_FILTER
253/* Returns 1 if the parent is an ancestor of the child. */
254static int is_ancestor(struct seccomp_filter *parent,
255 struct seccomp_filter *child)
256{
257 /* NULL is the root ancestor. */
258 if (parent == NULL)
259 return 1;
260 for (; child; child = child->prev)
261 if (child == parent)
262 return 1;
263 return 0;
264}
265
266/**
267 * seccomp_can_sync_threads: checks if all threads can be synchronized
268 *
269 * Expects sighand and cred_guard_mutex locks to be held.
270 *
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
273 * seccomp filter.
274 */
275static inline pid_t seccomp_can_sync_threads(void)
276{
277 struct task_struct *thread, *caller;
278
279 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
280 assert_spin_locked(¤t->sighand->siglock);
281
282 /* Validate all threads being eligible for synchronization. */
283 caller = current;
284 for_each_thread(caller, thread) {
285 pid_t failed;
286
287 /* Skip current, since it is initiating the sync. */
288 if (thread == caller)
289 continue;
290
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)))
295 continue;
296
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)))
301 failed = -ESRCH;
302 return failed;
303 }
304
305 return 0;
306}
307
308/**
309 * seccomp_sync_threads: sets all threads to use current's filter
310 *
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.
314 *
315 */
316static inline void seccomp_sync_threads(unsigned long flags)
317{
318 struct task_struct *thread, *caller;
319
320 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
321 assert_spin_locked(¤t->sighand->siglock);
322
323 /* Synchronize all threads. */
324 caller = current;
325 for_each_thread(caller, thread) {
326 /* Skip current, since it needs no changes. */
327 if (thread == caller)
328 continue;
329
330 /* Get a task reference for the new leaf node. */
331 get_seccomp_filter(caller);
332 /*
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.)
336 */
337 put_seccomp_filter(thread);
338 smp_store_release(&thread->seccomp.filter,
339 caller->seccomp.filter);
340
341 /*
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,
345 * then dies.
346 */
347 if (task_no_new_privs(caller))
348 task_set_no_new_privs(thread);
349
350 /*
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.
355 */
356 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
357 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
358 flags);
359 }
360}
361
362/**
363 * seccomp_prepare_filter: Prepares a seccomp filter for use.
364 * @fprog: BPF program to install
365 *
366 * Returns filter on success or an ERR_PTR on failure.
367 */
368static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
369{
370 struct seccomp_filter *sfilter;
371 int ret;
372 const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE);
373
374 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
375 return ERR_PTR(-EINVAL);
376
377 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
378
379 /*
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.
384 */
385 if (!task_no_new_privs(current) &&
386 security_capable_noaudit(current_cred(), current_user_ns(),
387 CAP_SYS_ADMIN) != 0)
388 return ERR_PTR(-EACCES);
389
390 /* Allocate a new seccomp_filter */
391 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
392 if (!sfilter)
393 return ERR_PTR(-ENOMEM);
394
395 ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
396 seccomp_check_filter, save_orig);
397 if (ret < 0) {
398 kfree(sfilter);
399 return ERR_PTR(ret);
400 }
401
402 refcount_set(&sfilter->usage, 1);
403
404 return sfilter;
405}
406
407/**
408 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
409 * @user_filter: pointer to the user data containing a sock_fprog.
410 *
411 * Returns 0 on success and non-zero otherwise.
412 */
413static struct seccomp_filter *
414seccomp_prepare_user_filter(const char __user *user_filter)
415{
416 struct sock_fprog fprog;
417 struct seccomp_filter *filter = ERR_PTR(-EFAULT);
418
419#ifdef CONFIG_COMPAT
420 if (in_compat_syscall()) {
421 struct compat_sock_fprog fprog32;
422 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
423 goto out;
424 fprog.len = fprog32.len;
425 fprog.filter = compat_ptr(fprog32.filter);
426 } else /* falls through to the if below. */
427#endif
428 if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
429 goto out;
430 filter = seccomp_prepare_filter(&fprog);
431out:
432 return filter;
433}
434
435/**
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
439 *
440 * Caller must be holding current->sighand->siglock lock.
441 *
442 * Returns 0 on success, -ve on error.
443 */
444static long seccomp_attach_filter(unsigned int flags,
445 struct seccomp_filter *filter)
446{
447 unsigned long total_insns;
448 struct seccomp_filter *walker;
449
450 assert_spin_locked(¤t->sighand->siglock);
451
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)
457 return -ENOMEM;
458
459 /* If thread sync has been requested, check that it is possible. */
460 if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
461 int ret;
462
463 ret = seccomp_can_sync_threads();
464 if (ret)
465 return ret;
466 }
467
468 /* Set log flag, if present. */
469 if (flags & SECCOMP_FILTER_FLAG_LOG)
470 filter->log = true;
471
472 /*
473 * If there is an existing filter, make it the prev and don't drop its
474 * task reference.
475 */
476 filter->prev = current->seccomp.filter;
477 current->seccomp.filter = filter;
478
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);
482
483 return 0;
484}
485
486static void __get_seccomp_filter(struct seccomp_filter *filter)
487{
488 /* Reference count is bounded by the number of total processes. */
489 refcount_inc(&filter->usage);
490}
491
492/* get_seccomp_filter - increments the reference count of the filter on @tsk */
493void get_seccomp_filter(struct task_struct *tsk)
494{
495 struct seccomp_filter *orig = tsk->seccomp.filter;
496 if (!orig)
497 return;
498 __get_seccomp_filter(orig);
499}
500
501static inline void seccomp_filter_free(struct seccomp_filter *filter)
502{
503 if (filter) {
504 bpf_prog_destroy(filter->prog);
505 kfree(filter);
506 }
507}
508
509static void __put_seccomp_filter(struct seccomp_filter *orig)
510{
511 /* Clean up single-reference branches iteratively. */
512 while (orig && refcount_dec_and_test(&orig->usage)) {
513 struct seccomp_filter *freeme = orig;
514 orig = orig->prev;
515 seccomp_filter_free(freeme);
516 }
517}
518
519/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
520void put_seccomp_filter(struct task_struct *tsk)
521{
522 __put_seccomp_filter(tsk->seccomp.filter);
523}
524
525static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
526{
527 clear_siginfo(info);
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;
534}
535
536/**
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)
540 *
541 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
542 */
543static void seccomp_send_sigsys(int syscall, int reason)
544{
545 struct siginfo info;
546 seccomp_init_siginfo(&info, syscall, reason);
547 force_sig_info(SIGSYS, &info, current);
548}
549#endif /* CONFIG_SECCOMP_FILTER */
550
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)
559
560static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
561 SECCOMP_LOG_KILL_THREAD |
562 SECCOMP_LOG_TRAP |
563 SECCOMP_LOG_ERRNO |
564 SECCOMP_LOG_TRACE |
565 SECCOMP_LOG_LOG;
566
567static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
568 bool requested)
569{
570 bool log = false;
571
572 switch (action) {
573 case SECCOMP_RET_ALLOW:
574 break;
575 case SECCOMP_RET_TRAP:
576 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
577 break;
578 case SECCOMP_RET_ERRNO:
579 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
580 break;
581 case SECCOMP_RET_TRACE:
582 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
583 break;
584 case SECCOMP_RET_LOG:
585 log = seccomp_actions_logged & SECCOMP_LOG_LOG;
586 break;
587 case SECCOMP_RET_KILL_THREAD:
588 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
589 break;
590 case SECCOMP_RET_KILL_PROCESS:
591 default:
592 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
593 }
594
595 /*
596 * Force an audit message to be emitted when the action is RET_KILL_*,
597 * RET_LOG, or the FILTER_FLAG_LOG bit was set and the action is
598 * allowed to be logged by the admin.
599 */
600 if (log)
601 return __audit_seccomp(syscall, signr, action);
602
603 /*
604 * Let the audit subsystem decide if the action should be audited based
605 * on whether the current task itself is being audited.
606 */
607 return audit_seccomp(syscall, signr, action);
608}
609
610/*
611 * Secure computing mode 1 allows only read/write/exit/sigreturn.
612 * To be fully secure this must be combined with rlimit
613 * to limit the stack allocations too.
614 */
615static const int mode1_syscalls[] = {
616 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
617 0, /* null terminated */
618};
619
620static void __secure_computing_strict(int this_syscall)
621{
622 const int *syscall_whitelist = mode1_syscalls;
623#ifdef CONFIG_COMPAT
624 if (in_compat_syscall())
625 syscall_whitelist = get_compat_mode1_syscalls();
626#endif
627 do {
628 if (*syscall_whitelist == this_syscall)
629 return;
630 } while (*++syscall_whitelist);
631
632#ifdef SECCOMP_DEBUG
633 dump_stack();
634#endif
635 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
636 do_exit(SIGKILL);
637}
638
639#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
640void secure_computing_strict(int this_syscall)
641{
642 int mode = current->seccomp.mode;
643
644 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
645 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
646 return;
647
648 if (mode == SECCOMP_MODE_DISABLED)
649 return;
650 else if (mode == SECCOMP_MODE_STRICT)
651 __secure_computing_strict(this_syscall);
652 else
653 BUG();
654}
655#else
656
657#ifdef CONFIG_SECCOMP_FILTER
658static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
659 const bool recheck_after_trace)
660{
661 u32 filter_ret, action;
662 struct seccomp_filter *match = NULL;
663 int data;
664
665 /*
666 * Make sure that any changes to mode from another thread have
667 * been seen after TIF_SECCOMP was seen.
668 */
669 rmb();
670
671 filter_ret = seccomp_run_filters(sd, &match);
672 data = filter_ret & SECCOMP_RET_DATA;
673 action = filter_ret & SECCOMP_RET_ACTION_FULL;
674
675 switch (action) {
676 case SECCOMP_RET_ERRNO:
677 /* Set low-order bits as an errno, capped at MAX_ERRNO. */
678 if (data > MAX_ERRNO)
679 data = MAX_ERRNO;
680 syscall_set_return_value(current, task_pt_regs(current),
681 -data, 0);
682 goto skip;
683
684 case SECCOMP_RET_TRAP:
685 /* Show the handler the original registers. */
686 syscall_rollback(current, task_pt_regs(current));
687 /* Let the filter pass back 16 bits of data. */
688 seccomp_send_sigsys(this_syscall, data);
689 goto skip;
690
691 case SECCOMP_RET_TRACE:
692 /* We've been put in this state by the ptracer already. */
693 if (recheck_after_trace)
694 return 0;
695
696 /* ENOSYS these calls if there is no tracer attached. */
697 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
698 syscall_set_return_value(current,
699 task_pt_regs(current),
700 -ENOSYS, 0);
701 goto skip;
702 }
703
704 /* Allow the BPF to provide the event message */
705 ptrace_event(PTRACE_EVENT_SECCOMP, data);
706 /*
707 * The delivery of a fatal signal during event
708 * notification may silently skip tracer notification,
709 * which could leave us with a potentially unmodified
710 * syscall that the tracer would have liked to have
711 * changed. Since the process is about to die, we just
712 * force the syscall to be skipped and let the signal
713 * kill the process and correctly handle any tracer exit
714 * notifications.
715 */
716 if (fatal_signal_pending(current))
717 goto skip;
718 /* Check if the tracer forced the syscall to be skipped. */
719 this_syscall = syscall_get_nr(current, task_pt_regs(current));
720 if (this_syscall < 0)
721 goto skip;
722
723 /*
724 * Recheck the syscall, since it may have changed. This
725 * intentionally uses a NULL struct seccomp_data to force
726 * a reload of all registers. This does not goto skip since
727 * a skip would have already been reported.
728 */
729 if (__seccomp_filter(this_syscall, NULL, true))
730 return -1;
731
732 return 0;
733
734 case SECCOMP_RET_LOG:
735 seccomp_log(this_syscall, 0, action, true);
736 return 0;
737
738 case SECCOMP_RET_ALLOW:
739 /*
740 * Note that the "match" filter will always be NULL for
741 * this action since SECCOMP_RET_ALLOW is the starting
742 * state in seccomp_run_filters().
743 */
744 return 0;
745
746 case SECCOMP_RET_KILL_THREAD:
747 case SECCOMP_RET_KILL_PROCESS:
748 default:
749 seccomp_log(this_syscall, SIGSYS, action, true);
750 /* Dump core only if this is the last remaining thread. */
751 if (action == SECCOMP_RET_KILL_PROCESS ||
752 get_nr_threads(current) == 1) {
753 siginfo_t info;
754
755 /* Show the original registers in the dump. */
756 syscall_rollback(current, task_pt_regs(current));
757 /* Trigger a manual coredump since do_exit skips it. */
758 seccomp_init_siginfo(&info, this_syscall, data);
759 do_coredump(&info);
760 }
761 if (action == SECCOMP_RET_KILL_PROCESS)
762 do_group_exit(SIGSYS);
763 else
764 do_exit(SIGSYS);
765 }
766
767 unreachable();
768
769skip:
770 seccomp_log(this_syscall, 0, action, match ? match->log : false);
771 return -1;
772}
773#else
774static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
775 const bool recheck_after_trace)
776{
777 BUG();
778}
779#endif
780
781int __secure_computing(const struct seccomp_data *sd)
782{
783 int mode = current->seccomp.mode;
784 int this_syscall;
785
786 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
787 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
788 return 0;
789
790 this_syscall = sd ? sd->nr :
791 syscall_get_nr(current, task_pt_regs(current));
792
793 switch (mode) {
794 case SECCOMP_MODE_STRICT:
795 __secure_computing_strict(this_syscall); /* may call do_exit */
796 return 0;
797 case SECCOMP_MODE_FILTER:
798 return __seccomp_filter(this_syscall, sd, false);
799 default:
800 BUG();
801 }
802}
803#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
804
805long prctl_get_seccomp(void)
806{
807 return current->seccomp.mode;
808}
809
810/**
811 * seccomp_set_mode_strict: internal function for setting strict seccomp
812 *
813 * Once current->seccomp.mode is non-zero, it may not be changed.
814 *
815 * Returns 0 on success or -EINVAL on failure.
816 */
817static long seccomp_set_mode_strict(void)
818{
819 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
820 long ret = -EINVAL;
821
822 spin_lock_irq(¤t->sighand->siglock);
823
824 if (!seccomp_may_assign_mode(seccomp_mode))
825 goto out;
826
827#ifdef TIF_NOTSC
828 disable_TSC();
829#endif
830 seccomp_assign_mode(current, seccomp_mode, 0);
831 ret = 0;
832
833out:
834 spin_unlock_irq(¤t->sighand->siglock);
835
836 return ret;
837}
838
839#ifdef CONFIG_SECCOMP_FILTER
840/**
841 * seccomp_set_mode_filter: internal function for setting seccomp filter
842 * @flags: flags to change filter behavior
843 * @filter: struct sock_fprog containing filter
844 *
845 * This function may be called repeatedly to install additional filters.
846 * Every filter successfully installed will be evaluated (in reverse order)
847 * for each system call the task makes.
848 *
849 * Once current->seccomp.mode is non-zero, it may not be changed.
850 *
851 * Returns 0 on success or -EINVAL on failure.
852 */
853static long seccomp_set_mode_filter(unsigned int flags,
854 const char __user *filter)
855{
856 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
857 struct seccomp_filter *prepared = NULL;
858 long ret = -EINVAL;
859
860 /* Validate flags. */
861 if (flags & ~SECCOMP_FILTER_FLAG_MASK)
862 return -EINVAL;
863
864 /* Prepare the new filter before holding any locks. */
865 prepared = seccomp_prepare_user_filter(filter);
866 if (IS_ERR(prepared))
867 return PTR_ERR(prepared);
868
869 /*
870 * Make sure we cannot change seccomp or nnp state via TSYNC
871 * while another thread is in the middle of calling exec.
872 */
873 if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
874 mutex_lock_killable(¤t->signal->cred_guard_mutex))
875 goto out_free;
876
877 spin_lock_irq(¤t->sighand->siglock);
878
879 if (!seccomp_may_assign_mode(seccomp_mode))
880 goto out;
881
882 ret = seccomp_attach_filter(flags, prepared);
883 if (ret)
884 goto out;
885 /* Do not free the successfully attached filter. */
886 prepared = NULL;
887
888 seccomp_assign_mode(current, seccomp_mode, flags);
889out:
890 spin_unlock_irq(¤t->sighand->siglock);
891 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
892 mutex_unlock(¤t->signal->cred_guard_mutex);
893out_free:
894 seccomp_filter_free(prepared);
895 return ret;
896}
897#else
898static inline long seccomp_set_mode_filter(unsigned int flags,
899 const char __user *filter)
900{
901 return -EINVAL;
902}
903#endif
904
905static long seccomp_get_action_avail(const char __user *uaction)
906{
907 u32 action;
908
909 if (copy_from_user(&action, uaction, sizeof(action)))
910 return -EFAULT;
911
912 switch (action) {
913 case SECCOMP_RET_KILL_PROCESS:
914 case SECCOMP_RET_KILL_THREAD:
915 case SECCOMP_RET_TRAP:
916 case SECCOMP_RET_ERRNO:
917 case SECCOMP_RET_TRACE:
918 case SECCOMP_RET_LOG:
919 case SECCOMP_RET_ALLOW:
920 break;
921 default:
922 return -EOPNOTSUPP;
923 }
924
925 return 0;
926}
927
928/* Common entry point for both prctl and syscall. */
929static long do_seccomp(unsigned int op, unsigned int flags,
930 const char __user *uargs)
931{
932 switch (op) {
933 case SECCOMP_SET_MODE_STRICT:
934 if (flags != 0 || uargs != NULL)
935 return -EINVAL;
936 return seccomp_set_mode_strict();
937 case SECCOMP_SET_MODE_FILTER:
938 return seccomp_set_mode_filter(flags, uargs);
939 case SECCOMP_GET_ACTION_AVAIL:
940 if (flags != 0)
941 return -EINVAL;
942
943 return seccomp_get_action_avail(uargs);
944 default:
945 return -EINVAL;
946 }
947}
948
949SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
950 const char __user *, uargs)
951{
952 return do_seccomp(op, flags, uargs);
953}
954
955/**
956 * prctl_set_seccomp: configures current->seccomp.mode
957 * @seccomp_mode: requested mode to use
958 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
959 *
960 * Returns 0 on success or -EINVAL on failure.
961 */
962long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
963{
964 unsigned int op;
965 char __user *uargs;
966
967 switch (seccomp_mode) {
968 case SECCOMP_MODE_STRICT:
969 op = SECCOMP_SET_MODE_STRICT;
970 /*
971 * Setting strict mode through prctl always ignored filter,
972 * so make sure it is always NULL here to pass the internal
973 * check in do_seccomp().
974 */
975 uargs = NULL;
976 break;
977 case SECCOMP_MODE_FILTER:
978 op = SECCOMP_SET_MODE_FILTER;
979 uargs = filter;
980 break;
981 default:
982 return -EINVAL;
983 }
984
985 /* prctl interface doesn't have flags, so they are always zero. */
986 return do_seccomp(op, 0, uargs);
987}
988
989#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
990static struct seccomp_filter *get_nth_filter(struct task_struct *task,
991 unsigned long filter_off)
992{
993 struct seccomp_filter *orig, *filter;
994 unsigned long count;
995
996 /*
997 * Note: this is only correct because the caller should be the (ptrace)
998 * tracer of the task, otherwise lock_task_sighand is needed.
999 */
1000 spin_lock_irq(&task->sighand->siglock);
1001
1002 if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
1003 spin_unlock_irq(&task->sighand->siglock);
1004 return ERR_PTR(-EINVAL);
1005 }
1006
1007 orig = task->seccomp.filter;
1008 __get_seccomp_filter(orig);
1009 spin_unlock_irq(&task->sighand->siglock);
1010
1011 count = 0;
1012 for (filter = orig; filter; filter = filter->prev)
1013 count++;
1014
1015 if (filter_off >= count) {
1016 filter = ERR_PTR(-ENOENT);
1017 goto out;
1018 }
1019
1020 count -= filter_off;
1021 for (filter = orig; filter && count > 1; filter = filter->prev)
1022 count--;
1023
1024 if (WARN_ON(count != 1 || !filter)) {
1025 filter = ERR_PTR(-ENOENT);
1026 goto out;
1027 }
1028
1029 __get_seccomp_filter(filter);
1030
1031out:
1032 __put_seccomp_filter(orig);
1033 return filter;
1034}
1035
1036long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
1037 void __user *data)
1038{
1039 struct seccomp_filter *filter;
1040 struct sock_fprog_kern *fprog;
1041 long ret;
1042
1043 if (!capable(CAP_SYS_ADMIN) ||
1044 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1045 return -EACCES;
1046 }
1047
1048 filter = get_nth_filter(task, filter_off);
1049 if (IS_ERR(filter))
1050 return PTR_ERR(filter);
1051
1052 fprog = filter->prog->orig_prog;
1053 if (!fprog) {
1054 /* This must be a new non-cBPF filter, since we save
1055 * every cBPF filter's orig_prog above when
1056 * CONFIG_CHECKPOINT_RESTORE is enabled.
1057 */
1058 ret = -EMEDIUMTYPE;
1059 goto out;
1060 }
1061
1062 ret = fprog->len;
1063 if (!data)
1064 goto out;
1065
1066 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
1067 ret = -EFAULT;
1068
1069out:
1070 __put_seccomp_filter(filter);
1071 return ret;
1072}
1073
1074long seccomp_get_metadata(struct task_struct *task,
1075 unsigned long size, void __user *data)
1076{
1077 long ret;
1078 struct seccomp_filter *filter;
1079 struct seccomp_metadata kmd = {};
1080
1081 if (!capable(CAP_SYS_ADMIN) ||
1082 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1083 return -EACCES;
1084 }
1085
1086 size = min_t(unsigned long, size, sizeof(kmd));
1087
1088 if (size < sizeof(kmd.filter_off))
1089 return -EINVAL;
1090
1091 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
1092 return -EFAULT;
1093
1094 filter = get_nth_filter(task, kmd.filter_off);
1095 if (IS_ERR(filter))
1096 return PTR_ERR(filter);
1097
1098 if (filter->log)
1099 kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
1100
1101 ret = size;
1102 if (copy_to_user(data, &kmd, size))
1103 ret = -EFAULT;
1104
1105 __put_seccomp_filter(filter);
1106 return ret;
1107}
1108#endif
1109
1110#ifdef CONFIG_SYSCTL
1111
1112/* Human readable action names for friendly sysctl interaction */
1113#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
1114#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
1115#define SECCOMP_RET_TRAP_NAME "trap"
1116#define SECCOMP_RET_ERRNO_NAME "errno"
1117#define SECCOMP_RET_TRACE_NAME "trace"
1118#define SECCOMP_RET_LOG_NAME "log"
1119#define SECCOMP_RET_ALLOW_NAME "allow"
1120
1121static const char seccomp_actions_avail[] =
1122 SECCOMP_RET_KILL_PROCESS_NAME " "
1123 SECCOMP_RET_KILL_THREAD_NAME " "
1124 SECCOMP_RET_TRAP_NAME " "
1125 SECCOMP_RET_ERRNO_NAME " "
1126 SECCOMP_RET_TRACE_NAME " "
1127 SECCOMP_RET_LOG_NAME " "
1128 SECCOMP_RET_ALLOW_NAME;
1129
1130struct seccomp_log_name {
1131 u32 log;
1132 const char *name;
1133};
1134
1135static const struct seccomp_log_name seccomp_log_names[] = {
1136 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
1137 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
1138 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
1139 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
1140 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
1141 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
1142 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
1143 { }
1144};
1145
1146static bool seccomp_names_from_actions_logged(char *names, size_t size,
1147 u32 actions_logged)
1148{
1149 const struct seccomp_log_name *cur;
1150 bool append_space = false;
1151
1152 for (cur = seccomp_log_names; cur->name && size; cur++) {
1153 ssize_t ret;
1154
1155 if (!(actions_logged & cur->log))
1156 continue;
1157
1158 if (append_space) {
1159 ret = strscpy(names, " ", size);
1160 if (ret < 0)
1161 return false;
1162
1163 names += ret;
1164 size -= ret;
1165 } else
1166 append_space = true;
1167
1168 ret = strscpy(names, cur->name, size);
1169 if (ret < 0)
1170 return false;
1171
1172 names += ret;
1173 size -= ret;
1174 }
1175
1176 return true;
1177}
1178
1179static bool seccomp_action_logged_from_name(u32 *action_logged,
1180 const char *name)
1181{
1182 const struct seccomp_log_name *cur;
1183
1184 for (cur = seccomp_log_names; cur->name; cur++) {
1185 if (!strcmp(cur->name, name)) {
1186 *action_logged = cur->log;
1187 return true;
1188 }
1189 }
1190
1191 return false;
1192}
1193
1194static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
1195{
1196 char *name;
1197
1198 *actions_logged = 0;
1199 while ((name = strsep(&names, " ")) && *name) {
1200 u32 action_logged = 0;
1201
1202 if (!seccomp_action_logged_from_name(&action_logged, name))
1203 return false;
1204
1205 *actions_logged |= action_logged;
1206 }
1207
1208 return true;
1209}
1210
1211static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
1212 void __user *buffer, size_t *lenp,
1213 loff_t *ppos)
1214{
1215 char names[sizeof(seccomp_actions_avail)];
1216 struct ctl_table table;
1217 int ret;
1218
1219 if (write && !capable(CAP_SYS_ADMIN))
1220 return -EPERM;
1221
1222 memset(names, 0, sizeof(names));
1223
1224 if (!write) {
1225 if (!seccomp_names_from_actions_logged(names, sizeof(names),
1226 seccomp_actions_logged))
1227 return -EINVAL;
1228 }
1229
1230 table = *ro_table;
1231 table.data = names;
1232 table.maxlen = sizeof(names);
1233 ret = proc_dostring(&table, write, buffer, lenp, ppos);
1234 if (ret)
1235 return ret;
1236
1237 if (write) {
1238 u32 actions_logged;
1239
1240 if (!seccomp_actions_logged_from_names(&actions_logged,
1241 table.data))
1242 return -EINVAL;
1243
1244 if (actions_logged & SECCOMP_LOG_ALLOW)
1245 return -EINVAL;
1246
1247 seccomp_actions_logged = actions_logged;
1248 }
1249
1250 return 0;
1251}
1252
1253static struct ctl_path seccomp_sysctl_path[] = {
1254 { .procname = "kernel", },
1255 { .procname = "seccomp", },
1256 { }
1257};
1258
1259static struct ctl_table seccomp_sysctl_table[] = {
1260 {
1261 .procname = "actions_avail",
1262 .data = (void *) &seccomp_actions_avail,
1263 .maxlen = sizeof(seccomp_actions_avail),
1264 .mode = 0444,
1265 .proc_handler = proc_dostring,
1266 },
1267 {
1268 .procname = "actions_logged",
1269 .mode = 0644,
1270 .proc_handler = seccomp_actions_logged_handler,
1271 },
1272 { }
1273};
1274
1275static int __init seccomp_sysctl_init(void)
1276{
1277 struct ctl_table_header *hdr;
1278
1279 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
1280 if (!hdr)
1281 pr_warn("seccomp: sysctl registration failed\n");
1282 else
1283 kmemleak_not_leak(hdr);
1284
1285 return 0;
1286}
1287
1288device_initcall(seccomp_sysctl_init)
1289
1290#endif /* CONFIG_SYSCTL */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/kernel/seccomp.c
4 *
5 * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
6 *
7 * Copyright (C) 2012 Google, Inc.
8 * Will Drewry <wad@chromium.org>
9 *
10 * This defines a simple but solid secure-computing facility.
11 *
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.
15 */
16
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>
30
31#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
32#include <asm/syscall.h>
33#endif
34
35#ifdef CONFIG_SECCOMP_FILTER
36#include <linux/file.h>
37#include <linux/filter.h>
38#include <linux/pid.h>
39#include <linux/ptrace.h>
40#include <linux/security.h>
41#include <linux/tracehook.h>
42#include <linux/uaccess.h>
43#include <linux/anon_inodes.h>
44
45enum notify_state {
46 SECCOMP_NOTIFY_INIT,
47 SECCOMP_NOTIFY_SENT,
48 SECCOMP_NOTIFY_REPLIED,
49};
50
51struct seccomp_knotif {
52 /* The struct pid of the task whose filter triggered the notification */
53 struct task_struct *task;
54
55 /* The "cookie" for this request; this is unique for this filter. */
56 u64 id;
57
58 /*
59 * The seccomp data. This pointer is valid the entire time this
60 * notification is active, since it comes from __seccomp_filter which
61 * eclipses the entire lifecycle here.
62 */
63 const struct seccomp_data *data;
64
65 /*
66 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
67 * struct seccomp_knotif is created and starts out in INIT. Once the
68 * handler reads the notification off of an FD, it transitions to SENT.
69 * If a signal is received the state transitions back to INIT and
70 * another message is sent. When the userspace handler replies, state
71 * transitions to REPLIED.
72 */
73 enum notify_state state;
74
75 /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
76 int error;
77 long val;
78
79 /* Signals when this has entered SECCOMP_NOTIFY_REPLIED */
80 struct completion ready;
81
82 struct list_head list;
83};
84
85/**
86 * struct notification - container for seccomp userspace notifications. Since
87 * most seccomp filters will not have notification listeners attached and this
88 * structure is fairly large, we store the notification-specific stuff in a
89 * separate structure.
90 *
91 * @request: A semaphore that users of this notification can wait on for
92 * changes. Actual reads and writes are still controlled with
93 * filter->notify_lock.
94 * @next_id: The id of the next request.
95 * @notifications: A list of struct seccomp_knotif elements.
96 * @wqh: A wait queue for poll.
97 */
98struct notification {
99 struct semaphore request;
100 u64 next_id;
101 struct list_head notifications;
102 wait_queue_head_t wqh;
103};
104
105/**
106 * struct seccomp_filter - container for seccomp BPF programs
107 *
108 * @usage: reference count to manage the object lifetime.
109 * get/put helpers should be used when accessing an instance
110 * outside of a lifetime-guarded section. In general, this
111 * is only needed for handling filters shared across tasks.
112 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
113 * @prev: points to a previously installed, or inherited, filter
114 * @prog: the BPF program to evaluate
115 * @notif: the struct that holds all notification related information
116 * @notify_lock: A lock for all notification-related accesses.
117 *
118 * seccomp_filter objects are organized in a tree linked via the @prev
119 * pointer. For any task, it appears to be a singly-linked list starting
120 * with current->seccomp.filter, the most recently attached or inherited filter.
121 * However, multiple filters may share a @prev node, by way of fork(), which
122 * results in a unidirectional tree existing in memory. This is similar to
123 * how namespaces work.
124 *
125 * seccomp_filter objects should never be modified after being attached
126 * to a task_struct (other than @usage).
127 */
128struct seccomp_filter {
129 refcount_t usage;
130 bool log;
131 struct seccomp_filter *prev;
132 struct bpf_prog *prog;
133 struct notification *notif;
134 struct mutex notify_lock;
135};
136
137/* Limit any path through the tree to 256KB worth of instructions. */
138#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
139
140/*
141 * Endianness is explicitly ignored and left for BPF program authors to manage
142 * as per the specific architecture.
143 */
144static void populate_seccomp_data(struct seccomp_data *sd)
145{
146 struct task_struct *task = current;
147 struct pt_regs *regs = task_pt_regs(task);
148 unsigned long args[6];
149
150 sd->nr = syscall_get_nr(task, regs);
151 sd->arch = syscall_get_arch(task);
152 syscall_get_arguments(task, regs, args);
153 sd->args[0] = args[0];
154 sd->args[1] = args[1];
155 sd->args[2] = args[2];
156 sd->args[3] = args[3];
157 sd->args[4] = args[4];
158 sd->args[5] = args[5];
159 sd->instruction_pointer = KSTK_EIP(task);
160}
161
162/**
163 * seccomp_check_filter - verify seccomp filter code
164 * @filter: filter to verify
165 * @flen: length of filter
166 *
167 * Takes a previously checked filter (by bpf_check_classic) and
168 * redirects all filter code that loads struct sk_buff data
169 * and related data through seccomp_bpf_load. It also
170 * enforces length and alignment checking of those loads.
171 *
172 * Returns 0 if the rule set is legal or -EINVAL if not.
173 */
174static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
175{
176 int pc;
177 for (pc = 0; pc < flen; pc++) {
178 struct sock_filter *ftest = &filter[pc];
179 u16 code = ftest->code;
180 u32 k = ftest->k;
181
182 switch (code) {
183 case BPF_LD | BPF_W | BPF_ABS:
184 ftest->code = BPF_LDX | BPF_W | BPF_ABS;
185 /* 32-bit aligned and not out of bounds. */
186 if (k >= sizeof(struct seccomp_data) || k & 3)
187 return -EINVAL;
188 continue;
189 case BPF_LD | BPF_W | BPF_LEN:
190 ftest->code = BPF_LD | BPF_IMM;
191 ftest->k = sizeof(struct seccomp_data);
192 continue;
193 case BPF_LDX | BPF_W | BPF_LEN:
194 ftest->code = BPF_LDX | BPF_IMM;
195 ftest->k = sizeof(struct seccomp_data);
196 continue;
197 /* Explicitly include allowed calls. */
198 case BPF_RET | BPF_K:
199 case BPF_RET | BPF_A:
200 case BPF_ALU | BPF_ADD | BPF_K:
201 case BPF_ALU | BPF_ADD | BPF_X:
202 case BPF_ALU | BPF_SUB | BPF_K:
203 case BPF_ALU | BPF_SUB | BPF_X:
204 case BPF_ALU | BPF_MUL | BPF_K:
205 case BPF_ALU | BPF_MUL | BPF_X:
206 case BPF_ALU | BPF_DIV | BPF_K:
207 case BPF_ALU | BPF_DIV | BPF_X:
208 case BPF_ALU | BPF_AND | BPF_K:
209 case BPF_ALU | BPF_AND | BPF_X:
210 case BPF_ALU | BPF_OR | BPF_K:
211 case BPF_ALU | BPF_OR | BPF_X:
212 case BPF_ALU | BPF_XOR | BPF_K:
213 case BPF_ALU | BPF_XOR | BPF_X:
214 case BPF_ALU | BPF_LSH | BPF_K:
215 case BPF_ALU | BPF_LSH | BPF_X:
216 case BPF_ALU | BPF_RSH | BPF_K:
217 case BPF_ALU | BPF_RSH | BPF_X:
218 case BPF_ALU | BPF_NEG:
219 case BPF_LD | BPF_IMM:
220 case BPF_LDX | BPF_IMM:
221 case BPF_MISC | BPF_TAX:
222 case BPF_MISC | BPF_TXA:
223 case BPF_LD | BPF_MEM:
224 case BPF_LDX | BPF_MEM:
225 case BPF_ST:
226 case BPF_STX:
227 case BPF_JMP | BPF_JA:
228 case BPF_JMP | BPF_JEQ | BPF_K:
229 case BPF_JMP | BPF_JEQ | BPF_X:
230 case BPF_JMP | BPF_JGE | BPF_K:
231 case BPF_JMP | BPF_JGE | BPF_X:
232 case BPF_JMP | BPF_JGT | BPF_K:
233 case BPF_JMP | BPF_JGT | BPF_X:
234 case BPF_JMP | BPF_JSET | BPF_K:
235 case BPF_JMP | BPF_JSET | BPF_X:
236 continue;
237 default:
238 return -EINVAL;
239 }
240 }
241 return 0;
242}
243
244/**
245 * seccomp_run_filters - evaluates all seccomp filters against @sd
246 * @sd: optional seccomp data to be passed to filters
247 * @match: stores struct seccomp_filter that resulted in the return value,
248 * unless filter returned SECCOMP_RET_ALLOW, in which case it will
249 * be unchanged.
250 *
251 * Returns valid seccomp BPF response codes.
252 */
253#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
254static u32 seccomp_run_filters(const struct seccomp_data *sd,
255 struct seccomp_filter **match)
256{
257 u32 ret = SECCOMP_RET_ALLOW;
258 /* Make sure cross-thread synced filter points somewhere sane. */
259 struct seccomp_filter *f =
260 READ_ONCE(current->seccomp.filter);
261
262 /* Ensure unexpected behavior doesn't result in failing open. */
263 if (WARN_ON(f == NULL))
264 return SECCOMP_RET_KILL_PROCESS;
265
266 /*
267 * All filters in the list are evaluated and the lowest BPF return
268 * value always takes priority (ignoring the DATA).
269 */
270 preempt_disable();
271 for (; f; f = f->prev) {
272 u32 cur_ret = BPF_PROG_RUN(f->prog, sd);
273
274 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
275 ret = cur_ret;
276 *match = f;
277 }
278 }
279 preempt_enable();
280 return ret;
281}
282#endif /* CONFIG_SECCOMP_FILTER */
283
284static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
285{
286 assert_spin_locked(¤t->sighand->siglock);
287
288 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
289 return false;
290
291 return true;
292}
293
294void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
295
296static inline void seccomp_assign_mode(struct task_struct *task,
297 unsigned long seccomp_mode,
298 unsigned long flags)
299{
300 assert_spin_locked(&task->sighand->siglock);
301
302 task->seccomp.mode = seccomp_mode;
303 /*
304 * Make sure TIF_SECCOMP cannot be set before the mode (and
305 * filter) is set.
306 */
307 smp_mb__before_atomic();
308 /* Assume default seccomp processes want spec flaw mitigation. */
309 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
310 arch_seccomp_spec_mitigate(task);
311 set_tsk_thread_flag(task, TIF_SECCOMP);
312}
313
314#ifdef CONFIG_SECCOMP_FILTER
315/* Returns 1 if the parent is an ancestor of the child. */
316static int is_ancestor(struct seccomp_filter *parent,
317 struct seccomp_filter *child)
318{
319 /* NULL is the root ancestor. */
320 if (parent == NULL)
321 return 1;
322 for (; child; child = child->prev)
323 if (child == parent)
324 return 1;
325 return 0;
326}
327
328/**
329 * seccomp_can_sync_threads: checks if all threads can be synchronized
330 *
331 * Expects sighand and cred_guard_mutex locks to be held.
332 *
333 * Returns 0 on success, -ve on error, or the pid of a thread which was
334 * either not in the correct seccomp mode or did not have an ancestral
335 * seccomp filter.
336 */
337static inline pid_t seccomp_can_sync_threads(void)
338{
339 struct task_struct *thread, *caller;
340
341 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
342 assert_spin_locked(¤t->sighand->siglock);
343
344 /* Validate all threads being eligible for synchronization. */
345 caller = current;
346 for_each_thread(caller, thread) {
347 pid_t failed;
348
349 /* Skip current, since it is initiating the sync. */
350 if (thread == caller)
351 continue;
352
353 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
354 (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
355 is_ancestor(thread->seccomp.filter,
356 caller->seccomp.filter)))
357 continue;
358
359 /* Return the first thread that cannot be synchronized. */
360 failed = task_pid_vnr(thread);
361 /* If the pid cannot be resolved, then return -ESRCH */
362 if (WARN_ON(failed == 0))
363 failed = -ESRCH;
364 return failed;
365 }
366
367 return 0;
368}
369
370/**
371 * seccomp_sync_threads: sets all threads to use current's filter
372 *
373 * Expects sighand and cred_guard_mutex locks to be held, and for
374 * seccomp_can_sync_threads() to have returned success already
375 * without dropping the locks.
376 *
377 */
378static inline void seccomp_sync_threads(unsigned long flags)
379{
380 struct task_struct *thread, *caller;
381
382 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
383 assert_spin_locked(¤t->sighand->siglock);
384
385 /* Synchronize all threads. */
386 caller = current;
387 for_each_thread(caller, thread) {
388 /* Skip current, since it needs no changes. */
389 if (thread == caller)
390 continue;
391
392 /* Get a task reference for the new leaf node. */
393 get_seccomp_filter(caller);
394 /*
395 * Drop the task reference to the shared ancestor since
396 * current's path will hold a reference. (This also
397 * allows a put before the assignment.)
398 */
399 put_seccomp_filter(thread);
400 smp_store_release(&thread->seccomp.filter,
401 caller->seccomp.filter);
402
403 /*
404 * Don't let an unprivileged task work around
405 * the no_new_privs restriction by creating
406 * a thread that sets it up, enters seccomp,
407 * then dies.
408 */
409 if (task_no_new_privs(caller))
410 task_set_no_new_privs(thread);
411
412 /*
413 * Opt the other thread into seccomp if needed.
414 * As threads are considered to be trust-realm
415 * equivalent (see ptrace_may_access), it is safe to
416 * allow one thread to transition the other.
417 */
418 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
419 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
420 flags);
421 }
422}
423
424/**
425 * seccomp_prepare_filter: Prepares a seccomp filter for use.
426 * @fprog: BPF program to install
427 *
428 * Returns filter on success or an ERR_PTR on failure.
429 */
430static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
431{
432 struct seccomp_filter *sfilter;
433 int ret;
434 const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE);
435
436 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
437 return ERR_PTR(-EINVAL);
438
439 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
440
441 /*
442 * Installing a seccomp filter requires that the task has
443 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
444 * This avoids scenarios where unprivileged tasks can affect the
445 * behavior of privileged children.
446 */
447 if (!task_no_new_privs(current) &&
448 security_capable(current_cred(), current_user_ns(),
449 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0)
450 return ERR_PTR(-EACCES);
451
452 /* Allocate a new seccomp_filter */
453 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
454 if (!sfilter)
455 return ERR_PTR(-ENOMEM);
456
457 mutex_init(&sfilter->notify_lock);
458 ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
459 seccomp_check_filter, save_orig);
460 if (ret < 0) {
461 kfree(sfilter);
462 return ERR_PTR(ret);
463 }
464
465 refcount_set(&sfilter->usage, 1);
466
467 return sfilter;
468}
469
470/**
471 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
472 * @user_filter: pointer to the user data containing a sock_fprog.
473 *
474 * Returns 0 on success and non-zero otherwise.
475 */
476static struct seccomp_filter *
477seccomp_prepare_user_filter(const char __user *user_filter)
478{
479 struct sock_fprog fprog;
480 struct seccomp_filter *filter = ERR_PTR(-EFAULT);
481
482#ifdef CONFIG_COMPAT
483 if (in_compat_syscall()) {
484 struct compat_sock_fprog fprog32;
485 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
486 goto out;
487 fprog.len = fprog32.len;
488 fprog.filter = compat_ptr(fprog32.filter);
489 } else /* falls through to the if below. */
490#endif
491 if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
492 goto out;
493 filter = seccomp_prepare_filter(&fprog);
494out:
495 return filter;
496}
497
498/**
499 * seccomp_attach_filter: validate and attach filter
500 * @flags: flags to change filter behavior
501 * @filter: seccomp filter to add to the current process
502 *
503 * Caller must be holding current->sighand->siglock lock.
504 *
505 * Returns 0 on success, -ve on error, or
506 * - in TSYNC mode: the pid of a thread which was either not in the correct
507 * seccomp mode or did not have an ancestral seccomp filter
508 * - in NEW_LISTENER mode: the fd of the new listener
509 */
510static long seccomp_attach_filter(unsigned int flags,
511 struct seccomp_filter *filter)
512{
513 unsigned long total_insns;
514 struct seccomp_filter *walker;
515
516 assert_spin_locked(¤t->sighand->siglock);
517
518 /* Validate resulting filter length. */
519 total_insns = filter->prog->len;
520 for (walker = current->seccomp.filter; walker; walker = walker->prev)
521 total_insns += walker->prog->len + 4; /* 4 instr penalty */
522 if (total_insns > MAX_INSNS_PER_PATH)
523 return -ENOMEM;
524
525 /* If thread sync has been requested, check that it is possible. */
526 if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
527 int ret;
528
529 ret = seccomp_can_sync_threads();
530 if (ret)
531 return ret;
532 }
533
534 /* Set log flag, if present. */
535 if (flags & SECCOMP_FILTER_FLAG_LOG)
536 filter->log = true;
537
538 /*
539 * If there is an existing filter, make it the prev and don't drop its
540 * task reference.
541 */
542 filter->prev = current->seccomp.filter;
543 current->seccomp.filter = filter;
544
545 /* Now that the new filter is in place, synchronize to all threads. */
546 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
547 seccomp_sync_threads(flags);
548
549 return 0;
550}
551
552static void __get_seccomp_filter(struct seccomp_filter *filter)
553{
554 refcount_inc(&filter->usage);
555}
556
557/* get_seccomp_filter - increments the reference count of the filter on @tsk */
558void get_seccomp_filter(struct task_struct *tsk)
559{
560 struct seccomp_filter *orig = tsk->seccomp.filter;
561 if (!orig)
562 return;
563 __get_seccomp_filter(orig);
564}
565
566static inline void seccomp_filter_free(struct seccomp_filter *filter)
567{
568 if (filter) {
569 bpf_prog_destroy(filter->prog);
570 kfree(filter);
571 }
572}
573
574static void __put_seccomp_filter(struct seccomp_filter *orig)
575{
576 /* Clean up single-reference branches iteratively. */
577 while (orig && refcount_dec_and_test(&orig->usage)) {
578 struct seccomp_filter *freeme = orig;
579 orig = orig->prev;
580 seccomp_filter_free(freeme);
581 }
582}
583
584/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
585void put_seccomp_filter(struct task_struct *tsk)
586{
587 __put_seccomp_filter(tsk->seccomp.filter);
588}
589
590static void seccomp_init_siginfo(kernel_siginfo_t *info, int syscall, int reason)
591{
592 clear_siginfo(info);
593 info->si_signo = SIGSYS;
594 info->si_code = SYS_SECCOMP;
595 info->si_call_addr = (void __user *)KSTK_EIP(current);
596 info->si_errno = reason;
597 info->si_arch = syscall_get_arch(current);
598 info->si_syscall = syscall;
599}
600
601/**
602 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
603 * @syscall: syscall number to send to userland
604 * @reason: filter-supplied reason code to send to userland (via si_errno)
605 *
606 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
607 */
608static void seccomp_send_sigsys(int syscall, int reason)
609{
610 struct kernel_siginfo info;
611 seccomp_init_siginfo(&info, syscall, reason);
612 force_sig_info(&info);
613}
614#endif /* CONFIG_SECCOMP_FILTER */
615
616/* For use with seccomp_actions_logged */
617#define SECCOMP_LOG_KILL_PROCESS (1 << 0)
618#define SECCOMP_LOG_KILL_THREAD (1 << 1)
619#define SECCOMP_LOG_TRAP (1 << 2)
620#define SECCOMP_LOG_ERRNO (1 << 3)
621#define SECCOMP_LOG_TRACE (1 << 4)
622#define SECCOMP_LOG_LOG (1 << 5)
623#define SECCOMP_LOG_ALLOW (1 << 6)
624#define SECCOMP_LOG_USER_NOTIF (1 << 7)
625
626static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
627 SECCOMP_LOG_KILL_THREAD |
628 SECCOMP_LOG_TRAP |
629 SECCOMP_LOG_ERRNO |
630 SECCOMP_LOG_USER_NOTIF |
631 SECCOMP_LOG_TRACE |
632 SECCOMP_LOG_LOG;
633
634static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
635 bool requested)
636{
637 bool log = false;
638
639 switch (action) {
640 case SECCOMP_RET_ALLOW:
641 break;
642 case SECCOMP_RET_TRAP:
643 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
644 break;
645 case SECCOMP_RET_ERRNO:
646 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
647 break;
648 case SECCOMP_RET_TRACE:
649 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
650 break;
651 case SECCOMP_RET_USER_NOTIF:
652 log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
653 break;
654 case SECCOMP_RET_LOG:
655 log = seccomp_actions_logged & SECCOMP_LOG_LOG;
656 break;
657 case SECCOMP_RET_KILL_THREAD:
658 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
659 break;
660 case SECCOMP_RET_KILL_PROCESS:
661 default:
662 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
663 }
664
665 /*
666 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
667 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
668 * any action from being logged by removing the action name from the
669 * seccomp_actions_logged sysctl.
670 */
671 if (!log)
672 return;
673
674 audit_seccomp(syscall, signr, action);
675}
676
677/*
678 * Secure computing mode 1 allows only read/write/exit/sigreturn.
679 * To be fully secure this must be combined with rlimit
680 * to limit the stack allocations too.
681 */
682static const int mode1_syscalls[] = {
683 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
684 0, /* null terminated */
685};
686
687static void __secure_computing_strict(int this_syscall)
688{
689 const int *syscall_whitelist = mode1_syscalls;
690#ifdef CONFIG_COMPAT
691 if (in_compat_syscall())
692 syscall_whitelist = get_compat_mode1_syscalls();
693#endif
694 do {
695 if (*syscall_whitelist == this_syscall)
696 return;
697 } while (*++syscall_whitelist);
698
699#ifdef SECCOMP_DEBUG
700 dump_stack();
701#endif
702 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
703 do_exit(SIGKILL);
704}
705
706#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
707void secure_computing_strict(int this_syscall)
708{
709 int mode = current->seccomp.mode;
710
711 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
712 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
713 return;
714
715 if (mode == SECCOMP_MODE_DISABLED)
716 return;
717 else if (mode == SECCOMP_MODE_STRICT)
718 __secure_computing_strict(this_syscall);
719 else
720 BUG();
721}
722#else
723
724#ifdef CONFIG_SECCOMP_FILTER
725static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
726{
727 /*
728 * Note: overflow is ok here, the id just needs to be unique per
729 * filter.
730 */
731 lockdep_assert_held(&filter->notify_lock);
732 return filter->notif->next_id++;
733}
734
735static void seccomp_do_user_notification(int this_syscall,
736 struct seccomp_filter *match,
737 const struct seccomp_data *sd)
738{
739 int err;
740 long ret = 0;
741 struct seccomp_knotif n = {};
742
743 mutex_lock(&match->notify_lock);
744 err = -ENOSYS;
745 if (!match->notif)
746 goto out;
747
748 n.task = current;
749 n.state = SECCOMP_NOTIFY_INIT;
750 n.data = sd;
751 n.id = seccomp_next_notify_id(match);
752 init_completion(&n.ready);
753 list_add(&n.list, &match->notif->notifications);
754
755 up(&match->notif->request);
756 wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM);
757 mutex_unlock(&match->notify_lock);
758
759 /*
760 * This is where we wait for a reply from userspace.
761 */
762 err = wait_for_completion_interruptible(&n.ready);
763 mutex_lock(&match->notify_lock);
764 if (err == 0) {
765 ret = n.val;
766 err = n.error;
767 }
768
769 /*
770 * Note that it's possible the listener died in between the time when
771 * we were notified of a respons (or a signal) and when we were able to
772 * re-acquire the lock, so only delete from the list if the
773 * notification actually exists.
774 *
775 * Also note that this test is only valid because there's no way to
776 * *reattach* to a notifier right now. If one is added, we'll need to
777 * keep track of the notif itself and make sure they match here.
778 */
779 if (match->notif)
780 list_del(&n.list);
781out:
782 mutex_unlock(&match->notify_lock);
783 syscall_set_return_value(current, task_pt_regs(current),
784 err, ret);
785}
786
787static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
788 const bool recheck_after_trace)
789{
790 u32 filter_ret, action;
791 struct seccomp_filter *match = NULL;
792 int data;
793 struct seccomp_data sd_local;
794
795 /*
796 * Make sure that any changes to mode from another thread have
797 * been seen after TIF_SECCOMP was seen.
798 */
799 rmb();
800
801 if (!sd) {
802 populate_seccomp_data(&sd_local);
803 sd = &sd_local;
804 }
805
806 filter_ret = seccomp_run_filters(sd, &match);
807 data = filter_ret & SECCOMP_RET_DATA;
808 action = filter_ret & SECCOMP_RET_ACTION_FULL;
809
810 switch (action) {
811 case SECCOMP_RET_ERRNO:
812 /* Set low-order bits as an errno, capped at MAX_ERRNO. */
813 if (data > MAX_ERRNO)
814 data = MAX_ERRNO;
815 syscall_set_return_value(current, task_pt_regs(current),
816 -data, 0);
817 goto skip;
818
819 case SECCOMP_RET_TRAP:
820 /* Show the handler the original registers. */
821 syscall_rollback(current, task_pt_regs(current));
822 /* Let the filter pass back 16 bits of data. */
823 seccomp_send_sigsys(this_syscall, data);
824 goto skip;
825
826 case SECCOMP_RET_TRACE:
827 /* We've been put in this state by the ptracer already. */
828 if (recheck_after_trace)
829 return 0;
830
831 /* ENOSYS these calls if there is no tracer attached. */
832 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
833 syscall_set_return_value(current,
834 task_pt_regs(current),
835 -ENOSYS, 0);
836 goto skip;
837 }
838
839 /* Allow the BPF to provide the event message */
840 ptrace_event(PTRACE_EVENT_SECCOMP, data);
841 /*
842 * The delivery of a fatal signal during event
843 * notification may silently skip tracer notification,
844 * which could leave us with a potentially unmodified
845 * syscall that the tracer would have liked to have
846 * changed. Since the process is about to die, we just
847 * force the syscall to be skipped and let the signal
848 * kill the process and correctly handle any tracer exit
849 * notifications.
850 */
851 if (fatal_signal_pending(current))
852 goto skip;
853 /* Check if the tracer forced the syscall to be skipped. */
854 this_syscall = syscall_get_nr(current, task_pt_regs(current));
855 if (this_syscall < 0)
856 goto skip;
857
858 /*
859 * Recheck the syscall, since it may have changed. This
860 * intentionally uses a NULL struct seccomp_data to force
861 * a reload of all registers. This does not goto skip since
862 * a skip would have already been reported.
863 */
864 if (__seccomp_filter(this_syscall, NULL, true))
865 return -1;
866
867 return 0;
868
869 case SECCOMP_RET_USER_NOTIF:
870 seccomp_do_user_notification(this_syscall, match, sd);
871 goto skip;
872
873 case SECCOMP_RET_LOG:
874 seccomp_log(this_syscall, 0, action, true);
875 return 0;
876
877 case SECCOMP_RET_ALLOW:
878 /*
879 * Note that the "match" filter will always be NULL for
880 * this action since SECCOMP_RET_ALLOW is the starting
881 * state in seccomp_run_filters().
882 */
883 return 0;
884
885 case SECCOMP_RET_KILL_THREAD:
886 case SECCOMP_RET_KILL_PROCESS:
887 default:
888 seccomp_log(this_syscall, SIGSYS, action, true);
889 /* Dump core only if this is the last remaining thread. */
890 if (action == SECCOMP_RET_KILL_PROCESS ||
891 get_nr_threads(current) == 1) {
892 kernel_siginfo_t info;
893
894 /* Show the original registers in the dump. */
895 syscall_rollback(current, task_pt_regs(current));
896 /* Trigger a manual coredump since do_exit skips it. */
897 seccomp_init_siginfo(&info, this_syscall, data);
898 do_coredump(&info);
899 }
900 if (action == SECCOMP_RET_KILL_PROCESS)
901 do_group_exit(SIGSYS);
902 else
903 do_exit(SIGSYS);
904 }
905
906 unreachable();
907
908skip:
909 seccomp_log(this_syscall, 0, action, match ? match->log : false);
910 return -1;
911}
912#else
913static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
914 const bool recheck_after_trace)
915{
916 BUG();
917}
918#endif
919
920int __secure_computing(const struct seccomp_data *sd)
921{
922 int mode = current->seccomp.mode;
923 int this_syscall;
924
925 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
926 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
927 return 0;
928
929 this_syscall = sd ? sd->nr :
930 syscall_get_nr(current, task_pt_regs(current));
931
932 switch (mode) {
933 case SECCOMP_MODE_STRICT:
934 __secure_computing_strict(this_syscall); /* may call do_exit */
935 return 0;
936 case SECCOMP_MODE_FILTER:
937 return __seccomp_filter(this_syscall, sd, false);
938 default:
939 BUG();
940 }
941}
942#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
943
944long prctl_get_seccomp(void)
945{
946 return current->seccomp.mode;
947}
948
949/**
950 * seccomp_set_mode_strict: internal function for setting strict seccomp
951 *
952 * Once current->seccomp.mode is non-zero, it may not be changed.
953 *
954 * Returns 0 on success or -EINVAL on failure.
955 */
956static long seccomp_set_mode_strict(void)
957{
958 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
959 long ret = -EINVAL;
960
961 spin_lock_irq(¤t->sighand->siglock);
962
963 if (!seccomp_may_assign_mode(seccomp_mode))
964 goto out;
965
966#ifdef TIF_NOTSC
967 disable_TSC();
968#endif
969 seccomp_assign_mode(current, seccomp_mode, 0);
970 ret = 0;
971
972out:
973 spin_unlock_irq(¤t->sighand->siglock);
974
975 return ret;
976}
977
978#ifdef CONFIG_SECCOMP_FILTER
979static int seccomp_notify_release(struct inode *inode, struct file *file)
980{
981 struct seccomp_filter *filter = file->private_data;
982 struct seccomp_knotif *knotif;
983
984 if (!filter)
985 return 0;
986
987 mutex_lock(&filter->notify_lock);
988
989 /*
990 * If this file is being closed because e.g. the task who owned it
991 * died, let's wake everyone up who was waiting on us.
992 */
993 list_for_each_entry(knotif, &filter->notif->notifications, list) {
994 if (knotif->state == SECCOMP_NOTIFY_REPLIED)
995 continue;
996
997 knotif->state = SECCOMP_NOTIFY_REPLIED;
998 knotif->error = -ENOSYS;
999 knotif->val = 0;
1000
1001 complete(&knotif->ready);
1002 }
1003
1004 kfree(filter->notif);
1005 filter->notif = NULL;
1006 mutex_unlock(&filter->notify_lock);
1007 __put_seccomp_filter(filter);
1008 return 0;
1009}
1010
1011static long seccomp_notify_recv(struct seccomp_filter *filter,
1012 void __user *buf)
1013{
1014 struct seccomp_knotif *knotif = NULL, *cur;
1015 struct seccomp_notif unotif;
1016 ssize_t ret;
1017
1018 memset(&unotif, 0, sizeof(unotif));
1019
1020 ret = down_interruptible(&filter->notif->request);
1021 if (ret < 0)
1022 return ret;
1023
1024 mutex_lock(&filter->notify_lock);
1025 list_for_each_entry(cur, &filter->notif->notifications, list) {
1026 if (cur->state == SECCOMP_NOTIFY_INIT) {
1027 knotif = cur;
1028 break;
1029 }
1030 }
1031
1032 /*
1033 * If we didn't find a notification, it could be that the task was
1034 * interrupted by a fatal signal between the time we were woken and
1035 * when we were able to acquire the rw lock.
1036 */
1037 if (!knotif) {
1038 ret = -ENOENT;
1039 goto out;
1040 }
1041
1042 unotif.id = knotif->id;
1043 unotif.pid = task_pid_vnr(knotif->task);
1044 unotif.data = *(knotif->data);
1045
1046 knotif->state = SECCOMP_NOTIFY_SENT;
1047 wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM);
1048 ret = 0;
1049out:
1050 mutex_unlock(&filter->notify_lock);
1051
1052 if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
1053 ret = -EFAULT;
1054
1055 /*
1056 * Userspace screwed up. To make sure that we keep this
1057 * notification alive, let's reset it back to INIT. It
1058 * may have died when we released the lock, so we need to make
1059 * sure it's still around.
1060 */
1061 knotif = NULL;
1062 mutex_lock(&filter->notify_lock);
1063 list_for_each_entry(cur, &filter->notif->notifications, list) {
1064 if (cur->id == unotif.id) {
1065 knotif = cur;
1066 break;
1067 }
1068 }
1069
1070 if (knotif) {
1071 knotif->state = SECCOMP_NOTIFY_INIT;
1072 up(&filter->notif->request);
1073 }
1074 mutex_unlock(&filter->notify_lock);
1075 }
1076
1077 return ret;
1078}
1079
1080static long seccomp_notify_send(struct seccomp_filter *filter,
1081 void __user *buf)
1082{
1083 struct seccomp_notif_resp resp = {};
1084 struct seccomp_knotif *knotif = NULL, *cur;
1085 long ret;
1086
1087 if (copy_from_user(&resp, buf, sizeof(resp)))
1088 return -EFAULT;
1089
1090 if (resp.flags)
1091 return -EINVAL;
1092
1093 ret = mutex_lock_interruptible(&filter->notify_lock);
1094 if (ret < 0)
1095 return ret;
1096
1097 list_for_each_entry(cur, &filter->notif->notifications, list) {
1098 if (cur->id == resp.id) {
1099 knotif = cur;
1100 break;
1101 }
1102 }
1103
1104 if (!knotif) {
1105 ret = -ENOENT;
1106 goto out;
1107 }
1108
1109 /* Allow exactly one reply. */
1110 if (knotif->state != SECCOMP_NOTIFY_SENT) {
1111 ret = -EINPROGRESS;
1112 goto out;
1113 }
1114
1115 ret = 0;
1116 knotif->state = SECCOMP_NOTIFY_REPLIED;
1117 knotif->error = resp.error;
1118 knotif->val = resp.val;
1119 complete(&knotif->ready);
1120out:
1121 mutex_unlock(&filter->notify_lock);
1122 return ret;
1123}
1124
1125static long seccomp_notify_id_valid(struct seccomp_filter *filter,
1126 void __user *buf)
1127{
1128 struct seccomp_knotif *knotif = NULL;
1129 u64 id;
1130 long ret;
1131
1132 if (copy_from_user(&id, buf, sizeof(id)))
1133 return -EFAULT;
1134
1135 ret = mutex_lock_interruptible(&filter->notify_lock);
1136 if (ret < 0)
1137 return ret;
1138
1139 ret = -ENOENT;
1140 list_for_each_entry(knotif, &filter->notif->notifications, list) {
1141 if (knotif->id == id) {
1142 if (knotif->state == SECCOMP_NOTIFY_SENT)
1143 ret = 0;
1144 goto out;
1145 }
1146 }
1147
1148out:
1149 mutex_unlock(&filter->notify_lock);
1150 return ret;
1151}
1152
1153static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
1154 unsigned long arg)
1155{
1156 struct seccomp_filter *filter = file->private_data;
1157 void __user *buf = (void __user *)arg;
1158
1159 switch (cmd) {
1160 case SECCOMP_IOCTL_NOTIF_RECV:
1161 return seccomp_notify_recv(filter, buf);
1162 case SECCOMP_IOCTL_NOTIF_SEND:
1163 return seccomp_notify_send(filter, buf);
1164 case SECCOMP_IOCTL_NOTIF_ID_VALID:
1165 return seccomp_notify_id_valid(filter, buf);
1166 default:
1167 return -EINVAL;
1168 }
1169}
1170
1171static __poll_t seccomp_notify_poll(struct file *file,
1172 struct poll_table_struct *poll_tab)
1173{
1174 struct seccomp_filter *filter = file->private_data;
1175 __poll_t ret = 0;
1176 struct seccomp_knotif *cur;
1177
1178 poll_wait(file, &filter->notif->wqh, poll_tab);
1179
1180 if (mutex_lock_interruptible(&filter->notify_lock) < 0)
1181 return EPOLLERR;
1182
1183 list_for_each_entry(cur, &filter->notif->notifications, list) {
1184 if (cur->state == SECCOMP_NOTIFY_INIT)
1185 ret |= EPOLLIN | EPOLLRDNORM;
1186 if (cur->state == SECCOMP_NOTIFY_SENT)
1187 ret |= EPOLLOUT | EPOLLWRNORM;
1188 if ((ret & EPOLLIN) && (ret & EPOLLOUT))
1189 break;
1190 }
1191
1192 mutex_unlock(&filter->notify_lock);
1193
1194 return ret;
1195}
1196
1197static const struct file_operations seccomp_notify_ops = {
1198 .poll = seccomp_notify_poll,
1199 .release = seccomp_notify_release,
1200 .unlocked_ioctl = seccomp_notify_ioctl,
1201};
1202
1203static struct file *init_listener(struct seccomp_filter *filter)
1204{
1205 struct file *ret = ERR_PTR(-EBUSY);
1206 struct seccomp_filter *cur;
1207
1208 for (cur = current->seccomp.filter; cur; cur = cur->prev) {
1209 if (cur->notif)
1210 goto out;
1211 }
1212
1213 ret = ERR_PTR(-ENOMEM);
1214 filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
1215 if (!filter->notif)
1216 goto out;
1217
1218 sema_init(&filter->notif->request, 0);
1219 filter->notif->next_id = get_random_u64();
1220 INIT_LIST_HEAD(&filter->notif->notifications);
1221 init_waitqueue_head(&filter->notif->wqh);
1222
1223 ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
1224 filter, O_RDWR);
1225 if (IS_ERR(ret))
1226 goto out_notif;
1227
1228 /* The file has a reference to it now */
1229 __get_seccomp_filter(filter);
1230
1231out_notif:
1232 if (IS_ERR(ret))
1233 kfree(filter->notif);
1234out:
1235 return ret;
1236}
1237
1238/**
1239 * seccomp_set_mode_filter: internal function for setting seccomp filter
1240 * @flags: flags to change filter behavior
1241 * @filter: struct sock_fprog containing filter
1242 *
1243 * This function may be called repeatedly to install additional filters.
1244 * Every filter successfully installed will be evaluated (in reverse order)
1245 * for each system call the task makes.
1246 *
1247 * Once current->seccomp.mode is non-zero, it may not be changed.
1248 *
1249 * Returns 0 on success or -EINVAL on failure.
1250 */
1251static long seccomp_set_mode_filter(unsigned int flags,
1252 const char __user *filter)
1253{
1254 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
1255 struct seccomp_filter *prepared = NULL;
1256 long ret = -EINVAL;
1257 int listener = -1;
1258 struct file *listener_f = NULL;
1259
1260 /* Validate flags. */
1261 if (flags & ~SECCOMP_FILTER_FLAG_MASK)
1262 return -EINVAL;
1263
1264 /*
1265 * In the successful case, NEW_LISTENER returns the new listener fd.
1266 * But in the failure case, TSYNC returns the thread that died. If you
1267 * combine these two flags, there's no way to tell whether something
1268 * succeeded or failed. So, let's disallow this combination.
1269 */
1270 if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
1271 (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER))
1272 return -EINVAL;
1273
1274 /* Prepare the new filter before holding any locks. */
1275 prepared = seccomp_prepare_user_filter(filter);
1276 if (IS_ERR(prepared))
1277 return PTR_ERR(prepared);
1278
1279 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1280 listener = get_unused_fd_flags(O_CLOEXEC);
1281 if (listener < 0) {
1282 ret = listener;
1283 goto out_free;
1284 }
1285
1286 listener_f = init_listener(prepared);
1287 if (IS_ERR(listener_f)) {
1288 put_unused_fd(listener);
1289 ret = PTR_ERR(listener_f);
1290 goto out_free;
1291 }
1292 }
1293
1294 /*
1295 * Make sure we cannot change seccomp or nnp state via TSYNC
1296 * while another thread is in the middle of calling exec.
1297 */
1298 if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
1299 mutex_lock_killable(¤t->signal->cred_guard_mutex))
1300 goto out_put_fd;
1301
1302 spin_lock_irq(¤t->sighand->siglock);
1303
1304 if (!seccomp_may_assign_mode(seccomp_mode))
1305 goto out;
1306
1307 ret = seccomp_attach_filter(flags, prepared);
1308 if (ret)
1309 goto out;
1310 /* Do not free the successfully attached filter. */
1311 prepared = NULL;
1312
1313 seccomp_assign_mode(current, seccomp_mode, flags);
1314out:
1315 spin_unlock_irq(¤t->sighand->siglock);
1316 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
1317 mutex_unlock(¤t->signal->cred_guard_mutex);
1318out_put_fd:
1319 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1320 if (ret) {
1321 listener_f->private_data = NULL;
1322 fput(listener_f);
1323 put_unused_fd(listener);
1324 } else {
1325 fd_install(listener, listener_f);
1326 ret = listener;
1327 }
1328 }
1329out_free:
1330 seccomp_filter_free(prepared);
1331 return ret;
1332}
1333#else
1334static inline long seccomp_set_mode_filter(unsigned int flags,
1335 const char __user *filter)
1336{
1337 return -EINVAL;
1338}
1339#endif
1340
1341static long seccomp_get_action_avail(const char __user *uaction)
1342{
1343 u32 action;
1344
1345 if (copy_from_user(&action, uaction, sizeof(action)))
1346 return -EFAULT;
1347
1348 switch (action) {
1349 case SECCOMP_RET_KILL_PROCESS:
1350 case SECCOMP_RET_KILL_THREAD:
1351 case SECCOMP_RET_TRAP:
1352 case SECCOMP_RET_ERRNO:
1353 case SECCOMP_RET_USER_NOTIF:
1354 case SECCOMP_RET_TRACE:
1355 case SECCOMP_RET_LOG:
1356 case SECCOMP_RET_ALLOW:
1357 break;
1358 default:
1359 return -EOPNOTSUPP;
1360 }
1361
1362 return 0;
1363}
1364
1365static long seccomp_get_notif_sizes(void __user *usizes)
1366{
1367 struct seccomp_notif_sizes sizes = {
1368 .seccomp_notif = sizeof(struct seccomp_notif),
1369 .seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
1370 .seccomp_data = sizeof(struct seccomp_data),
1371 };
1372
1373 if (copy_to_user(usizes, &sizes, sizeof(sizes)))
1374 return -EFAULT;
1375
1376 return 0;
1377}
1378
1379/* Common entry point for both prctl and syscall. */
1380static long do_seccomp(unsigned int op, unsigned int flags,
1381 void __user *uargs)
1382{
1383 switch (op) {
1384 case SECCOMP_SET_MODE_STRICT:
1385 if (flags != 0 || uargs != NULL)
1386 return -EINVAL;
1387 return seccomp_set_mode_strict();
1388 case SECCOMP_SET_MODE_FILTER:
1389 return seccomp_set_mode_filter(flags, uargs);
1390 case SECCOMP_GET_ACTION_AVAIL:
1391 if (flags != 0)
1392 return -EINVAL;
1393
1394 return seccomp_get_action_avail(uargs);
1395 case SECCOMP_GET_NOTIF_SIZES:
1396 if (flags != 0)
1397 return -EINVAL;
1398
1399 return seccomp_get_notif_sizes(uargs);
1400 default:
1401 return -EINVAL;
1402 }
1403}
1404
1405SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
1406 void __user *, uargs)
1407{
1408 return do_seccomp(op, flags, uargs);
1409}
1410
1411/**
1412 * prctl_set_seccomp: configures current->seccomp.mode
1413 * @seccomp_mode: requested mode to use
1414 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
1415 *
1416 * Returns 0 on success or -EINVAL on failure.
1417 */
1418long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
1419{
1420 unsigned int op;
1421 void __user *uargs;
1422
1423 switch (seccomp_mode) {
1424 case SECCOMP_MODE_STRICT:
1425 op = SECCOMP_SET_MODE_STRICT;
1426 /*
1427 * Setting strict mode through prctl always ignored filter,
1428 * so make sure it is always NULL here to pass the internal
1429 * check in do_seccomp().
1430 */
1431 uargs = NULL;
1432 break;
1433 case SECCOMP_MODE_FILTER:
1434 op = SECCOMP_SET_MODE_FILTER;
1435 uargs = filter;
1436 break;
1437 default:
1438 return -EINVAL;
1439 }
1440
1441 /* prctl interface doesn't have flags, so they are always zero. */
1442 return do_seccomp(op, 0, uargs);
1443}
1444
1445#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
1446static struct seccomp_filter *get_nth_filter(struct task_struct *task,
1447 unsigned long filter_off)
1448{
1449 struct seccomp_filter *orig, *filter;
1450 unsigned long count;
1451
1452 /*
1453 * Note: this is only correct because the caller should be the (ptrace)
1454 * tracer of the task, otherwise lock_task_sighand is needed.
1455 */
1456 spin_lock_irq(&task->sighand->siglock);
1457
1458 if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
1459 spin_unlock_irq(&task->sighand->siglock);
1460 return ERR_PTR(-EINVAL);
1461 }
1462
1463 orig = task->seccomp.filter;
1464 __get_seccomp_filter(orig);
1465 spin_unlock_irq(&task->sighand->siglock);
1466
1467 count = 0;
1468 for (filter = orig; filter; filter = filter->prev)
1469 count++;
1470
1471 if (filter_off >= count) {
1472 filter = ERR_PTR(-ENOENT);
1473 goto out;
1474 }
1475
1476 count -= filter_off;
1477 for (filter = orig; filter && count > 1; filter = filter->prev)
1478 count--;
1479
1480 if (WARN_ON(count != 1 || !filter)) {
1481 filter = ERR_PTR(-ENOENT);
1482 goto out;
1483 }
1484
1485 __get_seccomp_filter(filter);
1486
1487out:
1488 __put_seccomp_filter(orig);
1489 return filter;
1490}
1491
1492long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
1493 void __user *data)
1494{
1495 struct seccomp_filter *filter;
1496 struct sock_fprog_kern *fprog;
1497 long ret;
1498
1499 if (!capable(CAP_SYS_ADMIN) ||
1500 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1501 return -EACCES;
1502 }
1503
1504 filter = get_nth_filter(task, filter_off);
1505 if (IS_ERR(filter))
1506 return PTR_ERR(filter);
1507
1508 fprog = filter->prog->orig_prog;
1509 if (!fprog) {
1510 /* This must be a new non-cBPF filter, since we save
1511 * every cBPF filter's orig_prog above when
1512 * CONFIG_CHECKPOINT_RESTORE is enabled.
1513 */
1514 ret = -EMEDIUMTYPE;
1515 goto out;
1516 }
1517
1518 ret = fprog->len;
1519 if (!data)
1520 goto out;
1521
1522 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
1523 ret = -EFAULT;
1524
1525out:
1526 __put_seccomp_filter(filter);
1527 return ret;
1528}
1529
1530long seccomp_get_metadata(struct task_struct *task,
1531 unsigned long size, void __user *data)
1532{
1533 long ret;
1534 struct seccomp_filter *filter;
1535 struct seccomp_metadata kmd = {};
1536
1537 if (!capable(CAP_SYS_ADMIN) ||
1538 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1539 return -EACCES;
1540 }
1541
1542 size = min_t(unsigned long, size, sizeof(kmd));
1543
1544 if (size < sizeof(kmd.filter_off))
1545 return -EINVAL;
1546
1547 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
1548 return -EFAULT;
1549
1550 filter = get_nth_filter(task, kmd.filter_off);
1551 if (IS_ERR(filter))
1552 return PTR_ERR(filter);
1553
1554 if (filter->log)
1555 kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
1556
1557 ret = size;
1558 if (copy_to_user(data, &kmd, size))
1559 ret = -EFAULT;
1560
1561 __put_seccomp_filter(filter);
1562 return ret;
1563}
1564#endif
1565
1566#ifdef CONFIG_SYSCTL
1567
1568/* Human readable action names for friendly sysctl interaction */
1569#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
1570#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
1571#define SECCOMP_RET_TRAP_NAME "trap"
1572#define SECCOMP_RET_ERRNO_NAME "errno"
1573#define SECCOMP_RET_USER_NOTIF_NAME "user_notif"
1574#define SECCOMP_RET_TRACE_NAME "trace"
1575#define SECCOMP_RET_LOG_NAME "log"
1576#define SECCOMP_RET_ALLOW_NAME "allow"
1577
1578static const char seccomp_actions_avail[] =
1579 SECCOMP_RET_KILL_PROCESS_NAME " "
1580 SECCOMP_RET_KILL_THREAD_NAME " "
1581 SECCOMP_RET_TRAP_NAME " "
1582 SECCOMP_RET_ERRNO_NAME " "
1583 SECCOMP_RET_USER_NOTIF_NAME " "
1584 SECCOMP_RET_TRACE_NAME " "
1585 SECCOMP_RET_LOG_NAME " "
1586 SECCOMP_RET_ALLOW_NAME;
1587
1588struct seccomp_log_name {
1589 u32 log;
1590 const char *name;
1591};
1592
1593static const struct seccomp_log_name seccomp_log_names[] = {
1594 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
1595 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
1596 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
1597 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
1598 { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
1599 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
1600 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
1601 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
1602 { }
1603};
1604
1605static bool seccomp_names_from_actions_logged(char *names, size_t size,
1606 u32 actions_logged,
1607 const char *sep)
1608{
1609 const struct seccomp_log_name *cur;
1610 bool append_sep = false;
1611
1612 for (cur = seccomp_log_names; cur->name && size; cur++) {
1613 ssize_t ret;
1614
1615 if (!(actions_logged & cur->log))
1616 continue;
1617
1618 if (append_sep) {
1619 ret = strscpy(names, sep, size);
1620 if (ret < 0)
1621 return false;
1622
1623 names += ret;
1624 size -= ret;
1625 } else
1626 append_sep = true;
1627
1628 ret = strscpy(names, cur->name, size);
1629 if (ret < 0)
1630 return false;
1631
1632 names += ret;
1633 size -= ret;
1634 }
1635
1636 return true;
1637}
1638
1639static bool seccomp_action_logged_from_name(u32 *action_logged,
1640 const char *name)
1641{
1642 const struct seccomp_log_name *cur;
1643
1644 for (cur = seccomp_log_names; cur->name; cur++) {
1645 if (!strcmp(cur->name, name)) {
1646 *action_logged = cur->log;
1647 return true;
1648 }
1649 }
1650
1651 return false;
1652}
1653
1654static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
1655{
1656 char *name;
1657
1658 *actions_logged = 0;
1659 while ((name = strsep(&names, " ")) && *name) {
1660 u32 action_logged = 0;
1661
1662 if (!seccomp_action_logged_from_name(&action_logged, name))
1663 return false;
1664
1665 *actions_logged |= action_logged;
1666 }
1667
1668 return true;
1669}
1670
1671static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
1672 size_t *lenp, loff_t *ppos)
1673{
1674 char names[sizeof(seccomp_actions_avail)];
1675 struct ctl_table table;
1676
1677 memset(names, 0, sizeof(names));
1678
1679 if (!seccomp_names_from_actions_logged(names, sizeof(names),
1680 seccomp_actions_logged, " "))
1681 return -EINVAL;
1682
1683 table = *ro_table;
1684 table.data = names;
1685 table.maxlen = sizeof(names);
1686 return proc_dostring(&table, 0, buffer, lenp, ppos);
1687}
1688
1689static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
1690 size_t *lenp, loff_t *ppos, u32 *actions_logged)
1691{
1692 char names[sizeof(seccomp_actions_avail)];
1693 struct ctl_table table;
1694 int ret;
1695
1696 if (!capable(CAP_SYS_ADMIN))
1697 return -EPERM;
1698
1699 memset(names, 0, sizeof(names));
1700
1701 table = *ro_table;
1702 table.data = names;
1703 table.maxlen = sizeof(names);
1704 ret = proc_dostring(&table, 1, buffer, lenp, ppos);
1705 if (ret)
1706 return ret;
1707
1708 if (!seccomp_actions_logged_from_names(actions_logged, table.data))
1709 return -EINVAL;
1710
1711 if (*actions_logged & SECCOMP_LOG_ALLOW)
1712 return -EINVAL;
1713
1714 seccomp_actions_logged = *actions_logged;
1715 return 0;
1716}
1717
1718static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
1719 int ret)
1720{
1721 char names[sizeof(seccomp_actions_avail)];
1722 char old_names[sizeof(seccomp_actions_avail)];
1723 const char *new = names;
1724 const char *old = old_names;
1725
1726 if (!audit_enabled)
1727 return;
1728
1729 memset(names, 0, sizeof(names));
1730 memset(old_names, 0, sizeof(old_names));
1731
1732 if (ret)
1733 new = "?";
1734 else if (!actions_logged)
1735 new = "(none)";
1736 else if (!seccomp_names_from_actions_logged(names, sizeof(names),
1737 actions_logged, ","))
1738 new = "?";
1739
1740 if (!old_actions_logged)
1741 old = "(none)";
1742 else if (!seccomp_names_from_actions_logged(old_names,
1743 sizeof(old_names),
1744 old_actions_logged, ","))
1745 old = "?";
1746
1747 return audit_seccomp_actions_logged(new, old, !ret);
1748}
1749
1750static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
1751 void __user *buffer, size_t *lenp,
1752 loff_t *ppos)
1753{
1754 int ret;
1755
1756 if (write) {
1757 u32 actions_logged = 0;
1758 u32 old_actions_logged = seccomp_actions_logged;
1759
1760 ret = write_actions_logged(ro_table, buffer, lenp, ppos,
1761 &actions_logged);
1762 audit_actions_logged(actions_logged, old_actions_logged, ret);
1763 } else
1764 ret = read_actions_logged(ro_table, buffer, lenp, ppos);
1765
1766 return ret;
1767}
1768
1769static struct ctl_path seccomp_sysctl_path[] = {
1770 { .procname = "kernel", },
1771 { .procname = "seccomp", },
1772 { }
1773};
1774
1775static struct ctl_table seccomp_sysctl_table[] = {
1776 {
1777 .procname = "actions_avail",
1778 .data = (void *) &seccomp_actions_avail,
1779 .maxlen = sizeof(seccomp_actions_avail),
1780 .mode = 0444,
1781 .proc_handler = proc_dostring,
1782 },
1783 {
1784 .procname = "actions_logged",
1785 .mode = 0644,
1786 .proc_handler = seccomp_actions_logged_handler,
1787 },
1788 { }
1789};
1790
1791static int __init seccomp_sysctl_init(void)
1792{
1793 struct ctl_table_header *hdr;
1794
1795 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
1796 if (!hdr)
1797 pr_warn("seccomp: sysctl registration failed\n");
1798 else
1799 kmemleak_not_leak(hdr);
1800
1801 return 0;
1802}
1803
1804device_initcall(seccomp_sysctl_init)
1805
1806#endif /* CONFIG_SYSCTL */