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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#define pr_fmt(fmt) "seccomp: " fmt
17
18#include <linux/refcount.h>
19#include <linux/audit.h>
20#include <linux/compat.h>
21#include <linux/coredump.h>
22#include <linux/kmemleak.h>
23#include <linux/nospec.h>
24#include <linux/prctl.h>
25#include <linux/sched.h>
26#include <linux/sched/task_stack.h>
27#include <linux/seccomp.h>
28#include <linux/slab.h>
29#include <linux/syscalls.h>
30#include <linux/sysctl.h>
31
32/* Not exposed in headers: strictly internal use only. */
33#define SECCOMP_MODE_DEAD (SECCOMP_MODE_FILTER + 1)
34
35#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
36#include <asm/syscall.h>
37#endif
38
39#ifdef CONFIG_SECCOMP_FILTER
40#include <linux/file.h>
41#include <linux/filter.h>
42#include <linux/pid.h>
43#include <linux/ptrace.h>
44#include <linux/capability.h>
45#include <linux/uaccess.h>
46#include <linux/anon_inodes.h>
47#include <linux/lockdep.h>
48
49/*
50 * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the
51 * wrong direction flag in the ioctl number. This is the broken one,
52 * which the kernel needs to keep supporting until all userspaces stop
53 * using the wrong command number.
54 */
55#define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR SECCOMP_IOR(2, __u64)
56
57enum notify_state {
58 SECCOMP_NOTIFY_INIT,
59 SECCOMP_NOTIFY_SENT,
60 SECCOMP_NOTIFY_REPLIED,
61};
62
63struct seccomp_knotif {
64 /* The struct pid of the task whose filter triggered the notification */
65 struct task_struct *task;
66
67 /* The "cookie" for this request; this is unique for this filter. */
68 u64 id;
69
70 /*
71 * The seccomp data. This pointer is valid the entire time this
72 * notification is active, since it comes from __seccomp_filter which
73 * eclipses the entire lifecycle here.
74 */
75 const struct seccomp_data *data;
76
77 /*
78 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
79 * struct seccomp_knotif is created and starts out in INIT. Once the
80 * handler reads the notification off of an FD, it transitions to SENT.
81 * If a signal is received the state transitions back to INIT and
82 * another message is sent. When the userspace handler replies, state
83 * transitions to REPLIED.
84 */
85 enum notify_state state;
86
87 /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
88 int error;
89 long val;
90 u32 flags;
91
92 /*
93 * Signals when this has changed states, such as the listener
94 * dying, a new seccomp addfd message, or changing to REPLIED
95 */
96 struct completion ready;
97
98 struct list_head list;
99
100 /* outstanding addfd requests */
101 struct list_head addfd;
102};
103
104/**
105 * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages
106 *
107 * @file: A reference to the file to install in the other task
108 * @fd: The fd number to install it at. If the fd number is -1, it means the
109 * installing process should allocate the fd as normal.
110 * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC
111 * is allowed.
112 * @ioctl_flags: The flags used for the seccomp_addfd ioctl.
113 * @setfd: whether or not SECCOMP_ADDFD_FLAG_SETFD was set during notify_addfd
114 * @ret: The return value of the installing process. It is set to the fd num
115 * upon success (>= 0).
116 * @completion: Indicates that the installing process has completed fd
117 * installation, or gone away (either due to successful
118 * reply, or signal)
119 * @list: list_head for chaining seccomp_kaddfd together.
120 *
121 */
122struct seccomp_kaddfd {
123 struct file *file;
124 int fd;
125 unsigned int flags;
126 __u32 ioctl_flags;
127
128 union {
129 bool setfd;
130 /* To only be set on reply */
131 int ret;
132 };
133 struct completion completion;
134 struct list_head list;
135};
136
137/**
138 * struct notification - container for seccomp userspace notifications. Since
139 * most seccomp filters will not have notification listeners attached and this
140 * structure is fairly large, we store the notification-specific stuff in a
141 * separate structure.
142 *
143 * @requests: A semaphore that users of this notification can wait on for
144 * changes. Actual reads and writes are still controlled with
145 * filter->notify_lock.
146 * @flags: A set of SECCOMP_USER_NOTIF_FD_* flags.
147 * @next_id: The id of the next request.
148 * @notifications: A list of struct seccomp_knotif elements.
149 */
150
151struct notification {
152 atomic_t requests;
153 u32 flags;
154 u64 next_id;
155 struct list_head notifications;
156};
157
158#ifdef SECCOMP_ARCH_NATIVE
159/**
160 * struct action_cache - per-filter cache of seccomp actions per
161 * arch/syscall pair
162 *
163 * @allow_native: A bitmap where each bit represents whether the
164 * filter will always allow the syscall, for the
165 * native architecture.
166 * @allow_compat: A bitmap where each bit represents whether the
167 * filter will always allow the syscall, for the
168 * compat architecture.
169 */
170struct action_cache {
171 DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR);
172#ifdef SECCOMP_ARCH_COMPAT
173 DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR);
174#endif
175};
176#else
177struct action_cache { };
178
179static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
180 const struct seccomp_data *sd)
181{
182 return false;
183}
184
185static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
186{
187}
188#endif /* SECCOMP_ARCH_NATIVE */
189
190/**
191 * struct seccomp_filter - container for seccomp BPF programs
192 *
193 * @refs: Reference count to manage the object lifetime.
194 * A filter's reference count is incremented for each directly
195 * attached task, once for the dependent filter, and if
196 * requested for the user notifier. When @refs reaches zero,
197 * the filter can be freed.
198 * @users: A filter's @users count is incremented for each directly
199 * attached task (filter installation, fork(), thread_sync),
200 * and once for the dependent filter (tracked in filter->prev).
201 * When it reaches zero it indicates that no direct or indirect
202 * users of that filter exist. No new tasks can get associated with
203 * this filter after reaching 0. The @users count is always smaller
204 * or equal to @refs. Hence, reaching 0 for @users does not mean
205 * the filter can be freed.
206 * @cache: cache of arch/syscall mappings to actions
207 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
208 * @wait_killable_recv: Put notifying process in killable state once the
209 * notification is received by the userspace listener.
210 * @prev: points to a previously installed, or inherited, filter
211 * @prog: the BPF program to evaluate
212 * @notif: the struct that holds all notification related information
213 * @notify_lock: A lock for all notification-related accesses.
214 * @wqh: A wait queue for poll if a notifier is in use.
215 *
216 * seccomp_filter objects are organized in a tree linked via the @prev
217 * pointer. For any task, it appears to be a singly-linked list starting
218 * with current->seccomp.filter, the most recently attached or inherited filter.
219 * However, multiple filters may share a @prev node, by way of fork(), which
220 * results in a unidirectional tree existing in memory. This is similar to
221 * how namespaces work.
222 *
223 * seccomp_filter objects should never be modified after being attached
224 * to a task_struct (other than @refs).
225 */
226struct seccomp_filter {
227 refcount_t refs;
228 refcount_t users;
229 bool log;
230 bool wait_killable_recv;
231 struct action_cache cache;
232 struct seccomp_filter *prev;
233 struct bpf_prog *prog;
234 struct notification *notif;
235 struct mutex notify_lock;
236 wait_queue_head_t wqh;
237};
238
239/* Limit any path through the tree to 256KB worth of instructions. */
240#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
241
242/*
243 * Endianness is explicitly ignored and left for BPF program authors to manage
244 * as per the specific architecture.
245 */
246static void populate_seccomp_data(struct seccomp_data *sd)
247{
248 /*
249 * Instead of using current_pt_reg(), we're already doing the work
250 * to safely fetch "current", so just use "task" everywhere below.
251 */
252 struct task_struct *task = current;
253 struct pt_regs *regs = task_pt_regs(task);
254 unsigned long args[6];
255
256 sd->nr = syscall_get_nr(task, regs);
257 sd->arch = syscall_get_arch(task);
258 syscall_get_arguments(task, regs, args);
259 sd->args[0] = args[0];
260 sd->args[1] = args[1];
261 sd->args[2] = args[2];
262 sd->args[3] = args[3];
263 sd->args[4] = args[4];
264 sd->args[5] = args[5];
265 sd->instruction_pointer = KSTK_EIP(task);
266}
267
268/**
269 * seccomp_check_filter - verify seccomp filter code
270 * @filter: filter to verify
271 * @flen: length of filter
272 *
273 * Takes a previously checked filter (by bpf_check_classic) and
274 * redirects all filter code that loads struct sk_buff data
275 * and related data through seccomp_bpf_load. It also
276 * enforces length and alignment checking of those loads.
277 *
278 * Returns 0 if the rule set is legal or -EINVAL if not.
279 */
280static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
281{
282 int pc;
283 for (pc = 0; pc < flen; pc++) {
284 struct sock_filter *ftest = &filter[pc];
285 u16 code = ftest->code;
286 u32 k = ftest->k;
287
288 switch (code) {
289 case BPF_LD | BPF_W | BPF_ABS:
290 ftest->code = BPF_LDX | BPF_W | BPF_ABS;
291 /* 32-bit aligned and not out of bounds. */
292 if (k >= sizeof(struct seccomp_data) || k & 3)
293 return -EINVAL;
294 continue;
295 case BPF_LD | BPF_W | BPF_LEN:
296 ftest->code = BPF_LD | BPF_IMM;
297 ftest->k = sizeof(struct seccomp_data);
298 continue;
299 case BPF_LDX | BPF_W | BPF_LEN:
300 ftest->code = BPF_LDX | BPF_IMM;
301 ftest->k = sizeof(struct seccomp_data);
302 continue;
303 /* Explicitly include allowed calls. */
304 case BPF_RET | BPF_K:
305 case BPF_RET | BPF_A:
306 case BPF_ALU | BPF_ADD | BPF_K:
307 case BPF_ALU | BPF_ADD | BPF_X:
308 case BPF_ALU | BPF_SUB | BPF_K:
309 case BPF_ALU | BPF_SUB | BPF_X:
310 case BPF_ALU | BPF_MUL | BPF_K:
311 case BPF_ALU | BPF_MUL | BPF_X:
312 case BPF_ALU | BPF_DIV | BPF_K:
313 case BPF_ALU | BPF_DIV | BPF_X:
314 case BPF_ALU | BPF_AND | BPF_K:
315 case BPF_ALU | BPF_AND | BPF_X:
316 case BPF_ALU | BPF_OR | BPF_K:
317 case BPF_ALU | BPF_OR | BPF_X:
318 case BPF_ALU | BPF_XOR | BPF_K:
319 case BPF_ALU | BPF_XOR | BPF_X:
320 case BPF_ALU | BPF_LSH | BPF_K:
321 case BPF_ALU | BPF_LSH | BPF_X:
322 case BPF_ALU | BPF_RSH | BPF_K:
323 case BPF_ALU | BPF_RSH | BPF_X:
324 case BPF_ALU | BPF_NEG:
325 case BPF_LD | BPF_IMM:
326 case BPF_LDX | BPF_IMM:
327 case BPF_MISC | BPF_TAX:
328 case BPF_MISC | BPF_TXA:
329 case BPF_LD | BPF_MEM:
330 case BPF_LDX | BPF_MEM:
331 case BPF_ST:
332 case BPF_STX:
333 case BPF_JMP | BPF_JA:
334 case BPF_JMP | BPF_JEQ | BPF_K:
335 case BPF_JMP | BPF_JEQ | BPF_X:
336 case BPF_JMP | BPF_JGE | BPF_K:
337 case BPF_JMP | BPF_JGE | BPF_X:
338 case BPF_JMP | BPF_JGT | BPF_K:
339 case BPF_JMP | BPF_JGT | BPF_X:
340 case BPF_JMP | BPF_JSET | BPF_K:
341 case BPF_JMP | BPF_JSET | BPF_X:
342 continue;
343 default:
344 return -EINVAL;
345 }
346 }
347 return 0;
348}
349
350#ifdef SECCOMP_ARCH_NATIVE
351static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap,
352 size_t bitmap_size,
353 int syscall_nr)
354{
355 if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size))
356 return false;
357 syscall_nr = array_index_nospec(syscall_nr, bitmap_size);
358
359 return test_bit(syscall_nr, bitmap);
360}
361
362/**
363 * seccomp_cache_check_allow - lookup seccomp cache
364 * @sfilter: The seccomp filter
365 * @sd: The seccomp data to lookup the cache with
366 *
367 * Returns true if the seccomp_data is cached and allowed.
368 */
369static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
370 const struct seccomp_data *sd)
371{
372 int syscall_nr = sd->nr;
373 const struct action_cache *cache = &sfilter->cache;
374
375#ifndef SECCOMP_ARCH_COMPAT
376 /* A native-only architecture doesn't need to check sd->arch. */
377 return seccomp_cache_check_allow_bitmap(cache->allow_native,
378 SECCOMP_ARCH_NATIVE_NR,
379 syscall_nr);
380#else
381 if (likely(sd->arch == SECCOMP_ARCH_NATIVE))
382 return seccomp_cache_check_allow_bitmap(cache->allow_native,
383 SECCOMP_ARCH_NATIVE_NR,
384 syscall_nr);
385 if (likely(sd->arch == SECCOMP_ARCH_COMPAT))
386 return seccomp_cache_check_allow_bitmap(cache->allow_compat,
387 SECCOMP_ARCH_COMPAT_NR,
388 syscall_nr);
389#endif /* SECCOMP_ARCH_COMPAT */
390
391 WARN_ON_ONCE(true);
392 return false;
393}
394#endif /* SECCOMP_ARCH_NATIVE */
395
396#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
397/**
398 * seccomp_run_filters - evaluates all seccomp filters against @sd
399 * @sd: optional seccomp data to be passed to filters
400 * @match: stores struct seccomp_filter that resulted in the return value,
401 * unless filter returned SECCOMP_RET_ALLOW, in which case it will
402 * be unchanged.
403 *
404 * Returns valid seccomp BPF response codes.
405 */
406static u32 seccomp_run_filters(const struct seccomp_data *sd,
407 struct seccomp_filter **match)
408{
409 u32 ret = SECCOMP_RET_ALLOW;
410 /* Make sure cross-thread synced filter points somewhere sane. */
411 struct seccomp_filter *f =
412 READ_ONCE(current->seccomp.filter);
413
414 /* Ensure unexpected behavior doesn't result in failing open. */
415 if (WARN_ON(f == NULL))
416 return SECCOMP_RET_KILL_PROCESS;
417
418 if (seccomp_cache_check_allow(f, sd))
419 return SECCOMP_RET_ALLOW;
420
421 /*
422 * All filters in the list are evaluated and the lowest BPF return
423 * value always takes priority (ignoring the DATA).
424 */
425 for (; f; f = f->prev) {
426 u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd);
427
428 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
429 ret = cur_ret;
430 *match = f;
431 }
432 }
433 return ret;
434}
435#endif /* CONFIG_SECCOMP_FILTER */
436
437static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
438{
439 assert_spin_locked(¤t->sighand->siglock);
440
441 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
442 return false;
443
444 return true;
445}
446
447void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
448
449static inline void seccomp_assign_mode(struct task_struct *task,
450 unsigned long seccomp_mode,
451 unsigned long flags)
452{
453 assert_spin_locked(&task->sighand->siglock);
454
455 task->seccomp.mode = seccomp_mode;
456 /*
457 * Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and
458 * filter) is set.
459 */
460 smp_mb__before_atomic();
461 /* Assume default seccomp processes want spec flaw mitigation. */
462 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
463 arch_seccomp_spec_mitigate(task);
464 set_task_syscall_work(task, SECCOMP);
465}
466
467#ifdef CONFIG_SECCOMP_FILTER
468/* Returns 1 if the parent is an ancestor of the child. */
469static int is_ancestor(struct seccomp_filter *parent,
470 struct seccomp_filter *child)
471{
472 /* NULL is the root ancestor. */
473 if (parent == NULL)
474 return 1;
475 for (; child; child = child->prev)
476 if (child == parent)
477 return 1;
478 return 0;
479}
480
481/**
482 * seccomp_can_sync_threads: checks if all threads can be synchronized
483 *
484 * Expects sighand and cred_guard_mutex locks to be held.
485 *
486 * Returns 0 on success, -ve on error, or the pid of a thread which was
487 * either not in the correct seccomp mode or did not have an ancestral
488 * seccomp filter.
489 */
490static inline pid_t seccomp_can_sync_threads(void)
491{
492 struct task_struct *thread, *caller;
493
494 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
495 assert_spin_locked(¤t->sighand->siglock);
496
497 /* Validate all threads being eligible for synchronization. */
498 caller = current;
499 for_each_thread(caller, thread) {
500 pid_t failed;
501
502 /* Skip current, since it is initiating the sync. */
503 if (thread == caller)
504 continue;
505 /* Skip exited threads. */
506 if (thread->flags & PF_EXITING)
507 continue;
508
509 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
510 (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
511 is_ancestor(thread->seccomp.filter,
512 caller->seccomp.filter)))
513 continue;
514
515 /* Return the first thread that cannot be synchronized. */
516 failed = task_pid_vnr(thread);
517 /* If the pid cannot be resolved, then return -ESRCH */
518 if (WARN_ON(failed == 0))
519 failed = -ESRCH;
520 return failed;
521 }
522
523 return 0;
524}
525
526static inline void seccomp_filter_free(struct seccomp_filter *filter)
527{
528 if (filter) {
529 bpf_prog_destroy(filter->prog);
530 kfree(filter);
531 }
532}
533
534static void __seccomp_filter_orphan(struct seccomp_filter *orig)
535{
536 while (orig && refcount_dec_and_test(&orig->users)) {
537 if (waitqueue_active(&orig->wqh))
538 wake_up_poll(&orig->wqh, EPOLLHUP);
539 orig = orig->prev;
540 }
541}
542
543static void __put_seccomp_filter(struct seccomp_filter *orig)
544{
545 /* Clean up single-reference branches iteratively. */
546 while (orig && refcount_dec_and_test(&orig->refs)) {
547 struct seccomp_filter *freeme = orig;
548 orig = orig->prev;
549 seccomp_filter_free(freeme);
550 }
551}
552
553static void __seccomp_filter_release(struct seccomp_filter *orig)
554{
555 /* Notify about any unused filters in the task's former filter tree. */
556 __seccomp_filter_orphan(orig);
557 /* Finally drop all references to the task's former tree. */
558 __put_seccomp_filter(orig);
559}
560
561/**
562 * seccomp_filter_release - Detach the task from its filter tree,
563 * drop its reference count, and notify
564 * about unused filters
565 *
566 * @tsk: task the filter should be released from.
567 *
568 * This function should only be called when the task is exiting as
569 * it detaches it from its filter tree. PF_EXITING has to be set
570 * for the task.
571 */
572void seccomp_filter_release(struct task_struct *tsk)
573{
574 struct seccomp_filter *orig;
575
576 if (WARN_ON((tsk->flags & PF_EXITING) == 0))
577 return;
578
579 spin_lock_irq(&tsk->sighand->siglock);
580 orig = tsk->seccomp.filter;
581 /* Detach task from its filter tree. */
582 tsk->seccomp.filter = NULL;
583 spin_unlock_irq(&tsk->sighand->siglock);
584 __seccomp_filter_release(orig);
585}
586
587/**
588 * seccomp_sync_threads: sets all threads to use current's filter
589 *
590 * @flags: SECCOMP_FILTER_FLAG_* flags to set during sync.
591 *
592 * Expects sighand and cred_guard_mutex locks to be held, and for
593 * seccomp_can_sync_threads() to have returned success already
594 * without dropping the locks.
595 *
596 */
597static inline void seccomp_sync_threads(unsigned long flags)
598{
599 struct task_struct *thread, *caller;
600
601 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
602 assert_spin_locked(¤t->sighand->siglock);
603
604 /* Synchronize all threads. */
605 caller = current;
606 for_each_thread(caller, thread) {
607 /* Skip current, since it needs no changes. */
608 if (thread == caller)
609 continue;
610
611 /*
612 * Skip exited threads. seccomp_filter_release could have
613 * been already called for this task.
614 */
615 if (thread->flags & PF_EXITING)
616 continue;
617
618 /* Get a task reference for the new leaf node. */
619 get_seccomp_filter(caller);
620
621 /*
622 * Drop the task reference to the shared ancestor since
623 * current's path will hold a reference. (This also
624 * allows a put before the assignment.)
625 */
626 __seccomp_filter_release(thread->seccomp.filter);
627
628 /* Make our new filter tree visible. */
629 smp_store_release(&thread->seccomp.filter,
630 caller->seccomp.filter);
631 atomic_set(&thread->seccomp.filter_count,
632 atomic_read(&caller->seccomp.filter_count));
633
634 /*
635 * Don't let an unprivileged task work around
636 * the no_new_privs restriction by creating
637 * a thread that sets it up, enters seccomp,
638 * then dies.
639 */
640 if (task_no_new_privs(caller))
641 task_set_no_new_privs(thread);
642
643 /*
644 * Opt the other thread into seccomp if needed.
645 * As threads are considered to be trust-realm
646 * equivalent (see ptrace_may_access), it is safe to
647 * allow one thread to transition the other.
648 */
649 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
650 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
651 flags);
652 }
653}
654
655/**
656 * seccomp_prepare_filter: Prepares a seccomp filter for use.
657 * @fprog: BPF program to install
658 *
659 * Returns filter on success or an ERR_PTR on failure.
660 */
661static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
662{
663 struct seccomp_filter *sfilter;
664 int ret;
665 const bool save_orig =
666#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE)
667 true;
668#else
669 false;
670#endif
671
672 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
673 return ERR_PTR(-EINVAL);
674
675 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
676
677 /*
678 * Installing a seccomp filter requires that the task has
679 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
680 * This avoids scenarios where unprivileged tasks can affect the
681 * behavior of privileged children.
682 */
683 if (!task_no_new_privs(current) &&
684 !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
685 return ERR_PTR(-EACCES);
686
687 /* Allocate a new seccomp_filter */
688 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
689 if (!sfilter)
690 return ERR_PTR(-ENOMEM);
691
692 mutex_init(&sfilter->notify_lock);
693 ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
694 seccomp_check_filter, save_orig);
695 if (ret < 0) {
696 kfree(sfilter);
697 return ERR_PTR(ret);
698 }
699
700 refcount_set(&sfilter->refs, 1);
701 refcount_set(&sfilter->users, 1);
702 init_waitqueue_head(&sfilter->wqh);
703
704 return sfilter;
705}
706
707/**
708 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
709 * @user_filter: pointer to the user data containing a sock_fprog.
710 *
711 * Returns 0 on success and non-zero otherwise.
712 */
713static struct seccomp_filter *
714seccomp_prepare_user_filter(const char __user *user_filter)
715{
716 struct sock_fprog fprog;
717 struct seccomp_filter *filter = ERR_PTR(-EFAULT);
718
719#ifdef CONFIG_COMPAT
720 if (in_compat_syscall()) {
721 struct compat_sock_fprog fprog32;
722 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
723 goto out;
724 fprog.len = fprog32.len;
725 fprog.filter = compat_ptr(fprog32.filter);
726 } else /* falls through to the if below. */
727#endif
728 if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
729 goto out;
730 filter = seccomp_prepare_filter(&fprog);
731out:
732 return filter;
733}
734
735#ifdef SECCOMP_ARCH_NATIVE
736/**
737 * seccomp_is_const_allow - check if filter is constant allow with given data
738 * @fprog: The BPF programs
739 * @sd: The seccomp data to check against, only syscall number and arch
740 * number are considered constant.
741 */
742static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog,
743 struct seccomp_data *sd)
744{
745 unsigned int reg_value = 0;
746 unsigned int pc;
747 bool op_res;
748
749 if (WARN_ON_ONCE(!fprog))
750 return false;
751
752 /* Our single exception to filtering. */
753#ifdef __NR_uretprobe
754#ifdef SECCOMP_ARCH_COMPAT
755 if (sd->arch == SECCOMP_ARCH_NATIVE)
756#endif
757 if (sd->nr == __NR_uretprobe)
758 return true;
759#endif
760
761 for (pc = 0; pc < fprog->len; pc++) {
762 struct sock_filter *insn = &fprog->filter[pc];
763 u16 code = insn->code;
764 u32 k = insn->k;
765
766 switch (code) {
767 case BPF_LD | BPF_W | BPF_ABS:
768 switch (k) {
769 case offsetof(struct seccomp_data, nr):
770 reg_value = sd->nr;
771 break;
772 case offsetof(struct seccomp_data, arch):
773 reg_value = sd->arch;
774 break;
775 default:
776 /* can't optimize (non-constant value load) */
777 return false;
778 }
779 break;
780 case BPF_RET | BPF_K:
781 /* reached return with constant values only, check allow */
782 return k == SECCOMP_RET_ALLOW;
783 case BPF_JMP | BPF_JA:
784 pc += insn->k;
785 break;
786 case BPF_JMP | BPF_JEQ | BPF_K:
787 case BPF_JMP | BPF_JGE | BPF_K:
788 case BPF_JMP | BPF_JGT | BPF_K:
789 case BPF_JMP | BPF_JSET | BPF_K:
790 switch (BPF_OP(code)) {
791 case BPF_JEQ:
792 op_res = reg_value == k;
793 break;
794 case BPF_JGE:
795 op_res = reg_value >= k;
796 break;
797 case BPF_JGT:
798 op_res = reg_value > k;
799 break;
800 case BPF_JSET:
801 op_res = !!(reg_value & k);
802 break;
803 default:
804 /* can't optimize (unknown jump) */
805 return false;
806 }
807
808 pc += op_res ? insn->jt : insn->jf;
809 break;
810 case BPF_ALU | BPF_AND | BPF_K:
811 reg_value &= k;
812 break;
813 default:
814 /* can't optimize (unknown insn) */
815 return false;
816 }
817 }
818
819 /* ran off the end of the filter?! */
820 WARN_ON(1);
821 return false;
822}
823
824static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter,
825 void *bitmap, const void *bitmap_prev,
826 size_t bitmap_size, int arch)
827{
828 struct sock_fprog_kern *fprog = sfilter->prog->orig_prog;
829 struct seccomp_data sd;
830 int nr;
831
832 if (bitmap_prev) {
833 /* The new filter must be as restrictive as the last. */
834 bitmap_copy(bitmap, bitmap_prev, bitmap_size);
835 } else {
836 /* Before any filters, all syscalls are always allowed. */
837 bitmap_fill(bitmap, bitmap_size);
838 }
839
840 for (nr = 0; nr < bitmap_size; nr++) {
841 /* No bitmap change: not a cacheable action. */
842 if (!test_bit(nr, bitmap))
843 continue;
844
845 sd.nr = nr;
846 sd.arch = arch;
847
848 /* No bitmap change: continue to always allow. */
849 if (seccomp_is_const_allow(fprog, &sd))
850 continue;
851
852 /*
853 * Not a cacheable action: always run filters.
854 * atomic clear_bit() not needed, filter not visible yet.
855 */
856 __clear_bit(nr, bitmap);
857 }
858}
859
860/**
861 * seccomp_cache_prepare - emulate the filter to find cacheable syscalls
862 * @sfilter: The seccomp filter
863 *
864 * Returns 0 if successful or -errno if error occurred.
865 */
866static void seccomp_cache_prepare(struct seccomp_filter *sfilter)
867{
868 struct action_cache *cache = &sfilter->cache;
869 const struct action_cache *cache_prev =
870 sfilter->prev ? &sfilter->prev->cache : NULL;
871
872 seccomp_cache_prepare_bitmap(sfilter, cache->allow_native,
873 cache_prev ? cache_prev->allow_native : NULL,
874 SECCOMP_ARCH_NATIVE_NR,
875 SECCOMP_ARCH_NATIVE);
876
877#ifdef SECCOMP_ARCH_COMPAT
878 seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat,
879 cache_prev ? cache_prev->allow_compat : NULL,
880 SECCOMP_ARCH_COMPAT_NR,
881 SECCOMP_ARCH_COMPAT);
882#endif /* SECCOMP_ARCH_COMPAT */
883}
884#endif /* SECCOMP_ARCH_NATIVE */
885
886/**
887 * seccomp_attach_filter: validate and attach filter
888 * @flags: flags to change filter behavior
889 * @filter: seccomp filter to add to the current process
890 *
891 * Caller must be holding current->sighand->siglock lock.
892 *
893 * Returns 0 on success, -ve on error, or
894 * - in TSYNC mode: the pid of a thread which was either not in the correct
895 * seccomp mode or did not have an ancestral seccomp filter
896 * - in NEW_LISTENER mode: the fd of the new listener
897 */
898static long seccomp_attach_filter(unsigned int flags,
899 struct seccomp_filter *filter)
900{
901 unsigned long total_insns;
902 struct seccomp_filter *walker;
903
904 assert_spin_locked(¤t->sighand->siglock);
905
906 /* Validate resulting filter length. */
907 total_insns = filter->prog->len;
908 for (walker = current->seccomp.filter; walker; walker = walker->prev)
909 total_insns += walker->prog->len + 4; /* 4 instr penalty */
910 if (total_insns > MAX_INSNS_PER_PATH)
911 return -ENOMEM;
912
913 /* If thread sync has been requested, check that it is possible. */
914 if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
915 int ret;
916
917 ret = seccomp_can_sync_threads();
918 if (ret) {
919 if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH)
920 return -ESRCH;
921 else
922 return ret;
923 }
924 }
925
926 /* Set log flag, if present. */
927 if (flags & SECCOMP_FILTER_FLAG_LOG)
928 filter->log = true;
929
930 /* Set wait killable flag, if present. */
931 if (flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV)
932 filter->wait_killable_recv = true;
933
934 /*
935 * If there is an existing filter, make it the prev and don't drop its
936 * task reference.
937 */
938 filter->prev = current->seccomp.filter;
939 seccomp_cache_prepare(filter);
940 current->seccomp.filter = filter;
941 atomic_inc(¤t->seccomp.filter_count);
942
943 /* Now that the new filter is in place, synchronize to all threads. */
944 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
945 seccomp_sync_threads(flags);
946
947 return 0;
948}
949
950static void __get_seccomp_filter(struct seccomp_filter *filter)
951{
952 refcount_inc(&filter->refs);
953}
954
955/* get_seccomp_filter - increments the reference count of the filter on @tsk */
956void get_seccomp_filter(struct task_struct *tsk)
957{
958 struct seccomp_filter *orig = tsk->seccomp.filter;
959 if (!orig)
960 return;
961 __get_seccomp_filter(orig);
962 refcount_inc(&orig->users);
963}
964
965#endif /* CONFIG_SECCOMP_FILTER */
966
967/* For use with seccomp_actions_logged */
968#define SECCOMP_LOG_KILL_PROCESS (1 << 0)
969#define SECCOMP_LOG_KILL_THREAD (1 << 1)
970#define SECCOMP_LOG_TRAP (1 << 2)
971#define SECCOMP_LOG_ERRNO (1 << 3)
972#define SECCOMP_LOG_TRACE (1 << 4)
973#define SECCOMP_LOG_LOG (1 << 5)
974#define SECCOMP_LOG_ALLOW (1 << 6)
975#define SECCOMP_LOG_USER_NOTIF (1 << 7)
976
977static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
978 SECCOMP_LOG_KILL_THREAD |
979 SECCOMP_LOG_TRAP |
980 SECCOMP_LOG_ERRNO |
981 SECCOMP_LOG_USER_NOTIF |
982 SECCOMP_LOG_TRACE |
983 SECCOMP_LOG_LOG;
984
985static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
986 bool requested)
987{
988 bool log = false;
989
990 switch (action) {
991 case SECCOMP_RET_ALLOW:
992 break;
993 case SECCOMP_RET_TRAP:
994 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
995 break;
996 case SECCOMP_RET_ERRNO:
997 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
998 break;
999 case SECCOMP_RET_TRACE:
1000 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
1001 break;
1002 case SECCOMP_RET_USER_NOTIF:
1003 log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
1004 break;
1005 case SECCOMP_RET_LOG:
1006 log = seccomp_actions_logged & SECCOMP_LOG_LOG;
1007 break;
1008 case SECCOMP_RET_KILL_THREAD:
1009 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
1010 break;
1011 case SECCOMP_RET_KILL_PROCESS:
1012 default:
1013 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
1014 }
1015
1016 /*
1017 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
1018 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
1019 * any action from being logged by removing the action name from the
1020 * seccomp_actions_logged sysctl.
1021 */
1022 if (!log)
1023 return;
1024
1025 audit_seccomp(syscall, signr, action);
1026}
1027
1028/*
1029 * Secure computing mode 1 allows only read/write/exit/sigreturn.
1030 * To be fully secure this must be combined with rlimit
1031 * to limit the stack allocations too.
1032 */
1033static const int mode1_syscalls[] = {
1034 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
1035#ifdef __NR_uretprobe
1036 __NR_uretprobe,
1037#endif
1038 -1, /* negative terminated */
1039};
1040
1041static void __secure_computing_strict(int this_syscall)
1042{
1043 const int *allowed_syscalls = mode1_syscalls;
1044#ifdef CONFIG_COMPAT
1045 if (in_compat_syscall())
1046 allowed_syscalls = get_compat_mode1_syscalls();
1047#endif
1048 do {
1049 if (*allowed_syscalls == this_syscall)
1050 return;
1051 } while (*++allowed_syscalls != -1);
1052
1053#ifdef SECCOMP_DEBUG
1054 dump_stack();
1055#endif
1056 current->seccomp.mode = SECCOMP_MODE_DEAD;
1057 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
1058 do_exit(SIGKILL);
1059}
1060
1061#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
1062void secure_computing_strict(int this_syscall)
1063{
1064 int mode = current->seccomp.mode;
1065
1066 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1067 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1068 return;
1069
1070 if (mode == SECCOMP_MODE_DISABLED)
1071 return;
1072 else if (mode == SECCOMP_MODE_STRICT)
1073 __secure_computing_strict(this_syscall);
1074 else
1075 BUG();
1076}
1077#else
1078
1079#ifdef CONFIG_SECCOMP_FILTER
1080static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
1081{
1082 /*
1083 * Note: overflow is ok here, the id just needs to be unique per
1084 * filter.
1085 */
1086 lockdep_assert_held(&filter->notify_lock);
1087 return filter->notif->next_id++;
1088}
1089
1090static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n)
1091{
1092 int fd;
1093
1094 /*
1095 * Remove the notification, and reset the list pointers, indicating
1096 * that it has been handled.
1097 */
1098 list_del_init(&addfd->list);
1099 if (!addfd->setfd)
1100 fd = receive_fd(addfd->file, NULL, addfd->flags);
1101 else
1102 fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags);
1103 addfd->ret = fd;
1104
1105 if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) {
1106 /* If we fail reset and return an error to the notifier */
1107 if (fd < 0) {
1108 n->state = SECCOMP_NOTIFY_SENT;
1109 } else {
1110 /* Return the FD we just added */
1111 n->flags = 0;
1112 n->error = 0;
1113 n->val = fd;
1114 }
1115 }
1116
1117 /*
1118 * Mark the notification as completed. From this point, addfd mem
1119 * might be invalidated and we can't safely read it anymore.
1120 */
1121 complete(&addfd->completion);
1122}
1123
1124static bool should_sleep_killable(struct seccomp_filter *match,
1125 struct seccomp_knotif *n)
1126{
1127 return match->wait_killable_recv && n->state == SECCOMP_NOTIFY_SENT;
1128}
1129
1130static int seccomp_do_user_notification(int this_syscall,
1131 struct seccomp_filter *match,
1132 const struct seccomp_data *sd)
1133{
1134 int err;
1135 u32 flags = 0;
1136 long ret = 0;
1137 struct seccomp_knotif n = {};
1138 struct seccomp_kaddfd *addfd, *tmp;
1139
1140 mutex_lock(&match->notify_lock);
1141 err = -ENOSYS;
1142 if (!match->notif)
1143 goto out;
1144
1145 n.task = current;
1146 n.state = SECCOMP_NOTIFY_INIT;
1147 n.data = sd;
1148 n.id = seccomp_next_notify_id(match);
1149 init_completion(&n.ready);
1150 list_add_tail(&n.list, &match->notif->notifications);
1151 INIT_LIST_HEAD(&n.addfd);
1152
1153 atomic_inc(&match->notif->requests);
1154 if (match->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1155 wake_up_poll_on_current_cpu(&match->wqh, EPOLLIN | EPOLLRDNORM);
1156 else
1157 wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
1158
1159 /*
1160 * This is where we wait for a reply from userspace.
1161 */
1162 do {
1163 bool wait_killable = should_sleep_killable(match, &n);
1164
1165 mutex_unlock(&match->notify_lock);
1166 if (wait_killable)
1167 err = wait_for_completion_killable(&n.ready);
1168 else
1169 err = wait_for_completion_interruptible(&n.ready);
1170 mutex_lock(&match->notify_lock);
1171
1172 if (err != 0) {
1173 /*
1174 * Check to see if the notifcation got picked up and
1175 * whether we should switch to wait killable.
1176 */
1177 if (!wait_killable && should_sleep_killable(match, &n))
1178 continue;
1179
1180 goto interrupted;
1181 }
1182
1183 addfd = list_first_entry_or_null(&n.addfd,
1184 struct seccomp_kaddfd, list);
1185 /* Check if we were woken up by a addfd message */
1186 if (addfd)
1187 seccomp_handle_addfd(addfd, &n);
1188
1189 } while (n.state != SECCOMP_NOTIFY_REPLIED);
1190
1191 ret = n.val;
1192 err = n.error;
1193 flags = n.flags;
1194
1195interrupted:
1196 /* If there were any pending addfd calls, clear them out */
1197 list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
1198 /* The process went away before we got a chance to handle it */
1199 addfd->ret = -ESRCH;
1200 list_del_init(&addfd->list);
1201 complete(&addfd->completion);
1202 }
1203
1204 /*
1205 * Note that it's possible the listener died in between the time when
1206 * we were notified of a response (or a signal) and when we were able to
1207 * re-acquire the lock, so only delete from the list if the
1208 * notification actually exists.
1209 *
1210 * Also note that this test is only valid because there's no way to
1211 * *reattach* to a notifier right now. If one is added, we'll need to
1212 * keep track of the notif itself and make sure they match here.
1213 */
1214 if (match->notif)
1215 list_del(&n.list);
1216out:
1217 mutex_unlock(&match->notify_lock);
1218
1219 /* Userspace requests to continue the syscall. */
1220 if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1221 return 0;
1222
1223 syscall_set_return_value(current, current_pt_regs(),
1224 err, ret);
1225 return -1;
1226}
1227
1228static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
1229 const bool recheck_after_trace)
1230{
1231 u32 filter_ret, action;
1232 struct seccomp_filter *match = NULL;
1233 int data;
1234 struct seccomp_data sd_local;
1235
1236 /*
1237 * Make sure that any changes to mode from another thread have
1238 * been seen after SYSCALL_WORK_SECCOMP was seen.
1239 */
1240 smp_rmb();
1241
1242 if (!sd) {
1243 populate_seccomp_data(&sd_local);
1244 sd = &sd_local;
1245 }
1246
1247 filter_ret = seccomp_run_filters(sd, &match);
1248 data = filter_ret & SECCOMP_RET_DATA;
1249 action = filter_ret & SECCOMP_RET_ACTION_FULL;
1250
1251 switch (action) {
1252 case SECCOMP_RET_ERRNO:
1253 /* Set low-order bits as an errno, capped at MAX_ERRNO. */
1254 if (data > MAX_ERRNO)
1255 data = MAX_ERRNO;
1256 syscall_set_return_value(current, current_pt_regs(),
1257 -data, 0);
1258 goto skip;
1259
1260 case SECCOMP_RET_TRAP:
1261 /* Show the handler the original registers. */
1262 syscall_rollback(current, current_pt_regs());
1263 /* Let the filter pass back 16 bits of data. */
1264 force_sig_seccomp(this_syscall, data, false);
1265 goto skip;
1266
1267 case SECCOMP_RET_TRACE:
1268 /* We've been put in this state by the ptracer already. */
1269 if (recheck_after_trace)
1270 return 0;
1271
1272 /* ENOSYS these calls if there is no tracer attached. */
1273 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
1274 syscall_set_return_value(current,
1275 current_pt_regs(),
1276 -ENOSYS, 0);
1277 goto skip;
1278 }
1279
1280 /* Allow the BPF to provide the event message */
1281 ptrace_event(PTRACE_EVENT_SECCOMP, data);
1282 /*
1283 * The delivery of a fatal signal during event
1284 * notification may silently skip tracer notification,
1285 * which could leave us with a potentially unmodified
1286 * syscall that the tracer would have liked to have
1287 * changed. Since the process is about to die, we just
1288 * force the syscall to be skipped and let the signal
1289 * kill the process and correctly handle any tracer exit
1290 * notifications.
1291 */
1292 if (fatal_signal_pending(current))
1293 goto skip;
1294 /* Check if the tracer forced the syscall to be skipped. */
1295 this_syscall = syscall_get_nr(current, current_pt_regs());
1296 if (this_syscall < 0)
1297 goto skip;
1298
1299 /*
1300 * Recheck the syscall, since it may have changed. This
1301 * intentionally uses a NULL struct seccomp_data to force
1302 * a reload of all registers. This does not goto skip since
1303 * a skip would have already been reported.
1304 */
1305 if (__seccomp_filter(this_syscall, NULL, true))
1306 return -1;
1307
1308 return 0;
1309
1310 case SECCOMP_RET_USER_NOTIF:
1311 if (seccomp_do_user_notification(this_syscall, match, sd))
1312 goto skip;
1313
1314 return 0;
1315
1316 case SECCOMP_RET_LOG:
1317 seccomp_log(this_syscall, 0, action, true);
1318 return 0;
1319
1320 case SECCOMP_RET_ALLOW:
1321 /*
1322 * Note that the "match" filter will always be NULL for
1323 * this action since SECCOMP_RET_ALLOW is the starting
1324 * state in seccomp_run_filters().
1325 */
1326 return 0;
1327
1328 case SECCOMP_RET_KILL_THREAD:
1329 case SECCOMP_RET_KILL_PROCESS:
1330 default:
1331 current->seccomp.mode = SECCOMP_MODE_DEAD;
1332 seccomp_log(this_syscall, SIGSYS, action, true);
1333 /* Dump core only if this is the last remaining thread. */
1334 if (action != SECCOMP_RET_KILL_THREAD ||
1335 (atomic_read(¤t->signal->live) == 1)) {
1336 /* Show the original registers in the dump. */
1337 syscall_rollback(current, current_pt_regs());
1338 /* Trigger a coredump with SIGSYS */
1339 force_sig_seccomp(this_syscall, data, true);
1340 } else {
1341 do_exit(SIGSYS);
1342 }
1343 return -1; /* skip the syscall go directly to signal handling */
1344 }
1345
1346 unreachable();
1347
1348skip:
1349 seccomp_log(this_syscall, 0, action, match ? match->log : false);
1350 return -1;
1351}
1352#else
1353static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
1354 const bool recheck_after_trace)
1355{
1356 BUG();
1357
1358 return -1;
1359}
1360#endif
1361
1362int __secure_computing(const struct seccomp_data *sd)
1363{
1364 int mode = current->seccomp.mode;
1365 int this_syscall;
1366
1367 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1368 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1369 return 0;
1370
1371 this_syscall = sd ? sd->nr :
1372 syscall_get_nr(current, current_pt_regs());
1373
1374 switch (mode) {
1375 case SECCOMP_MODE_STRICT:
1376 __secure_computing_strict(this_syscall); /* may call do_exit */
1377 return 0;
1378 case SECCOMP_MODE_FILTER:
1379 return __seccomp_filter(this_syscall, sd, false);
1380 /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */
1381 case SECCOMP_MODE_DEAD:
1382 WARN_ON_ONCE(1);
1383 do_exit(SIGKILL);
1384 return -1;
1385 default:
1386 BUG();
1387 }
1388}
1389#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
1390
1391long prctl_get_seccomp(void)
1392{
1393 return current->seccomp.mode;
1394}
1395
1396/**
1397 * seccomp_set_mode_strict: internal function for setting strict seccomp
1398 *
1399 * Once current->seccomp.mode is non-zero, it may not be changed.
1400 *
1401 * Returns 0 on success or -EINVAL on failure.
1402 */
1403static long seccomp_set_mode_strict(void)
1404{
1405 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
1406 long ret = -EINVAL;
1407
1408 spin_lock_irq(¤t->sighand->siglock);
1409
1410 if (!seccomp_may_assign_mode(seccomp_mode))
1411 goto out;
1412
1413#ifdef TIF_NOTSC
1414 disable_TSC();
1415#endif
1416 seccomp_assign_mode(current, seccomp_mode, 0);
1417 ret = 0;
1418
1419out:
1420 spin_unlock_irq(¤t->sighand->siglock);
1421
1422 return ret;
1423}
1424
1425#ifdef CONFIG_SECCOMP_FILTER
1426static void seccomp_notify_free(struct seccomp_filter *filter)
1427{
1428 kfree(filter->notif);
1429 filter->notif = NULL;
1430}
1431
1432static void seccomp_notify_detach(struct seccomp_filter *filter)
1433{
1434 struct seccomp_knotif *knotif;
1435
1436 if (!filter)
1437 return;
1438
1439 mutex_lock(&filter->notify_lock);
1440
1441 /*
1442 * If this file is being closed because e.g. the task who owned it
1443 * died, let's wake everyone up who was waiting on us.
1444 */
1445 list_for_each_entry(knotif, &filter->notif->notifications, list) {
1446 if (knotif->state == SECCOMP_NOTIFY_REPLIED)
1447 continue;
1448
1449 knotif->state = SECCOMP_NOTIFY_REPLIED;
1450 knotif->error = -ENOSYS;
1451 knotif->val = 0;
1452
1453 /*
1454 * We do not need to wake up any pending addfd messages, as
1455 * the notifier will do that for us, as this just looks
1456 * like a standard reply.
1457 */
1458 complete(&knotif->ready);
1459 }
1460
1461 seccomp_notify_free(filter);
1462 mutex_unlock(&filter->notify_lock);
1463}
1464
1465static int seccomp_notify_release(struct inode *inode, struct file *file)
1466{
1467 struct seccomp_filter *filter = file->private_data;
1468
1469 seccomp_notify_detach(filter);
1470 __put_seccomp_filter(filter);
1471 return 0;
1472}
1473
1474/* must be called with notif_lock held */
1475static inline struct seccomp_knotif *
1476find_notification(struct seccomp_filter *filter, u64 id)
1477{
1478 struct seccomp_knotif *cur;
1479
1480 lockdep_assert_held(&filter->notify_lock);
1481
1482 list_for_each_entry(cur, &filter->notif->notifications, list) {
1483 if (cur->id == id)
1484 return cur;
1485 }
1486
1487 return NULL;
1488}
1489
1490static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync,
1491 void *key)
1492{
1493 /* Avoid a wakeup if event not interesting for us. */
1494 if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP)))
1495 return 0;
1496 return autoremove_wake_function(wait, mode, sync, key);
1497}
1498
1499static int recv_wait_event(struct seccomp_filter *filter)
1500{
1501 DEFINE_WAIT_FUNC(wait, recv_wake_function);
1502 int ret;
1503
1504 if (refcount_read(&filter->users) == 0)
1505 return 0;
1506
1507 if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
1508 return 0;
1509
1510 for (;;) {
1511 ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE);
1512
1513 if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
1514 break;
1515 if (refcount_read(&filter->users) == 0)
1516 break;
1517
1518 if (ret)
1519 return ret;
1520
1521 schedule();
1522 }
1523 finish_wait(&filter->wqh, &wait);
1524 return 0;
1525}
1526
1527static long seccomp_notify_recv(struct seccomp_filter *filter,
1528 void __user *buf)
1529{
1530 struct seccomp_knotif *knotif = NULL, *cur;
1531 struct seccomp_notif unotif;
1532 ssize_t ret;
1533
1534 /* Verify that we're not given garbage to keep struct extensible. */
1535 ret = check_zeroed_user(buf, sizeof(unotif));
1536 if (ret < 0)
1537 return ret;
1538 if (!ret)
1539 return -EINVAL;
1540
1541 memset(&unotif, 0, sizeof(unotif));
1542
1543 ret = recv_wait_event(filter);
1544 if (ret < 0)
1545 return ret;
1546
1547 mutex_lock(&filter->notify_lock);
1548 list_for_each_entry(cur, &filter->notif->notifications, list) {
1549 if (cur->state == SECCOMP_NOTIFY_INIT) {
1550 knotif = cur;
1551 break;
1552 }
1553 }
1554
1555 /*
1556 * If we didn't find a notification, it could be that the task was
1557 * interrupted by a fatal signal between the time we were woken and
1558 * when we were able to acquire the rw lock.
1559 */
1560 if (!knotif) {
1561 ret = -ENOENT;
1562 goto out;
1563 }
1564
1565 unotif.id = knotif->id;
1566 unotif.pid = task_pid_vnr(knotif->task);
1567 unotif.data = *(knotif->data);
1568
1569 knotif->state = SECCOMP_NOTIFY_SENT;
1570 wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM);
1571 ret = 0;
1572out:
1573 mutex_unlock(&filter->notify_lock);
1574
1575 if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
1576 ret = -EFAULT;
1577
1578 /*
1579 * Userspace screwed up. To make sure that we keep this
1580 * notification alive, let's reset it back to INIT. It
1581 * may have died when we released the lock, so we need to make
1582 * sure it's still around.
1583 */
1584 mutex_lock(&filter->notify_lock);
1585 knotif = find_notification(filter, unotif.id);
1586 if (knotif) {
1587 /* Reset the process to make sure it's not stuck */
1588 if (should_sleep_killable(filter, knotif))
1589 complete(&knotif->ready);
1590 knotif->state = SECCOMP_NOTIFY_INIT;
1591 atomic_inc(&filter->notif->requests);
1592 wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM);
1593 }
1594 mutex_unlock(&filter->notify_lock);
1595 }
1596
1597 return ret;
1598}
1599
1600static long seccomp_notify_send(struct seccomp_filter *filter,
1601 void __user *buf)
1602{
1603 struct seccomp_notif_resp resp = {};
1604 struct seccomp_knotif *knotif;
1605 long ret;
1606
1607 if (copy_from_user(&resp, buf, sizeof(resp)))
1608 return -EFAULT;
1609
1610 if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1611 return -EINVAL;
1612
1613 if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) &&
1614 (resp.error || resp.val))
1615 return -EINVAL;
1616
1617 ret = mutex_lock_interruptible(&filter->notify_lock);
1618 if (ret < 0)
1619 return ret;
1620
1621 knotif = find_notification(filter, resp.id);
1622 if (!knotif) {
1623 ret = -ENOENT;
1624 goto out;
1625 }
1626
1627 /* Allow exactly one reply. */
1628 if (knotif->state != SECCOMP_NOTIFY_SENT) {
1629 ret = -EINPROGRESS;
1630 goto out;
1631 }
1632
1633 ret = 0;
1634 knotif->state = SECCOMP_NOTIFY_REPLIED;
1635 knotif->error = resp.error;
1636 knotif->val = resp.val;
1637 knotif->flags = resp.flags;
1638 if (filter->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1639 complete_on_current_cpu(&knotif->ready);
1640 else
1641 complete(&knotif->ready);
1642out:
1643 mutex_unlock(&filter->notify_lock);
1644 return ret;
1645}
1646
1647static long seccomp_notify_id_valid(struct seccomp_filter *filter,
1648 void __user *buf)
1649{
1650 struct seccomp_knotif *knotif;
1651 u64 id;
1652 long ret;
1653
1654 if (copy_from_user(&id, buf, sizeof(id)))
1655 return -EFAULT;
1656
1657 ret = mutex_lock_interruptible(&filter->notify_lock);
1658 if (ret < 0)
1659 return ret;
1660
1661 knotif = find_notification(filter, id);
1662 if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
1663 ret = 0;
1664 else
1665 ret = -ENOENT;
1666
1667 mutex_unlock(&filter->notify_lock);
1668 return ret;
1669}
1670
1671static long seccomp_notify_set_flags(struct seccomp_filter *filter,
1672 unsigned long flags)
1673{
1674 long ret;
1675
1676 if (flags & ~SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1677 return -EINVAL;
1678
1679 ret = mutex_lock_interruptible(&filter->notify_lock);
1680 if (ret < 0)
1681 return ret;
1682 filter->notif->flags = flags;
1683 mutex_unlock(&filter->notify_lock);
1684 return 0;
1685}
1686
1687static long seccomp_notify_addfd(struct seccomp_filter *filter,
1688 struct seccomp_notif_addfd __user *uaddfd,
1689 unsigned int size)
1690{
1691 struct seccomp_notif_addfd addfd;
1692 struct seccomp_knotif *knotif;
1693 struct seccomp_kaddfd kaddfd;
1694 int ret;
1695
1696 BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0);
1697 BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST);
1698
1699 if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE)
1700 return -EINVAL;
1701
1702 ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size);
1703 if (ret)
1704 return ret;
1705
1706 if (addfd.newfd_flags & ~O_CLOEXEC)
1707 return -EINVAL;
1708
1709 if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND))
1710 return -EINVAL;
1711
1712 if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
1713 return -EINVAL;
1714
1715 kaddfd.file = fget(addfd.srcfd);
1716 if (!kaddfd.file)
1717 return -EBADF;
1718
1719 kaddfd.ioctl_flags = addfd.flags;
1720 kaddfd.flags = addfd.newfd_flags;
1721 kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD;
1722 kaddfd.fd = addfd.newfd;
1723 init_completion(&kaddfd.completion);
1724
1725 ret = mutex_lock_interruptible(&filter->notify_lock);
1726 if (ret < 0)
1727 goto out;
1728
1729 knotif = find_notification(filter, addfd.id);
1730 if (!knotif) {
1731 ret = -ENOENT;
1732 goto out_unlock;
1733 }
1734
1735 /*
1736 * We do not want to allow for FD injection to occur before the
1737 * notification has been picked up by a userspace handler, or after
1738 * the notification has been replied to.
1739 */
1740 if (knotif->state != SECCOMP_NOTIFY_SENT) {
1741 ret = -EINPROGRESS;
1742 goto out_unlock;
1743 }
1744
1745 if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) {
1746 /*
1747 * Disallow queuing an atomic addfd + send reply while there are
1748 * some addfd requests still to process.
1749 *
1750 * There is no clear reason to support it and allows us to keep
1751 * the loop on the other side straight-forward.
1752 */
1753 if (!list_empty(&knotif->addfd)) {
1754 ret = -EBUSY;
1755 goto out_unlock;
1756 }
1757
1758 /* Allow exactly only one reply */
1759 knotif->state = SECCOMP_NOTIFY_REPLIED;
1760 }
1761
1762 list_add(&kaddfd.list, &knotif->addfd);
1763 complete(&knotif->ready);
1764 mutex_unlock(&filter->notify_lock);
1765
1766 /* Now we wait for it to be processed or be interrupted */
1767 ret = wait_for_completion_interruptible(&kaddfd.completion);
1768 if (ret == 0) {
1769 /*
1770 * We had a successful completion. The other side has already
1771 * removed us from the addfd queue, and
1772 * wait_for_completion_interruptible has a memory barrier upon
1773 * success that lets us read this value directly without
1774 * locking.
1775 */
1776 ret = kaddfd.ret;
1777 goto out;
1778 }
1779
1780 mutex_lock(&filter->notify_lock);
1781 /*
1782 * Even though we were woken up by a signal and not a successful
1783 * completion, a completion may have happened in the mean time.
1784 *
1785 * We need to check again if the addfd request has been handled,
1786 * and if not, we will remove it from the queue.
1787 */
1788 if (list_empty(&kaddfd.list))
1789 ret = kaddfd.ret;
1790 else
1791 list_del(&kaddfd.list);
1792
1793out_unlock:
1794 mutex_unlock(&filter->notify_lock);
1795out:
1796 fput(kaddfd.file);
1797
1798 return ret;
1799}
1800
1801static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
1802 unsigned long arg)
1803{
1804 struct seccomp_filter *filter = file->private_data;
1805 void __user *buf = (void __user *)arg;
1806
1807 /* Fixed-size ioctls */
1808 switch (cmd) {
1809 case SECCOMP_IOCTL_NOTIF_RECV:
1810 return seccomp_notify_recv(filter, buf);
1811 case SECCOMP_IOCTL_NOTIF_SEND:
1812 return seccomp_notify_send(filter, buf);
1813 case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
1814 case SECCOMP_IOCTL_NOTIF_ID_VALID:
1815 return seccomp_notify_id_valid(filter, buf);
1816 case SECCOMP_IOCTL_NOTIF_SET_FLAGS:
1817 return seccomp_notify_set_flags(filter, arg);
1818 }
1819
1820 /* Extensible Argument ioctls */
1821#define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
1822 switch (EA_IOCTL(cmd)) {
1823 case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
1824 return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
1825 default:
1826 return -EINVAL;
1827 }
1828}
1829
1830static __poll_t seccomp_notify_poll(struct file *file,
1831 struct poll_table_struct *poll_tab)
1832{
1833 struct seccomp_filter *filter = file->private_data;
1834 __poll_t ret = 0;
1835 struct seccomp_knotif *cur;
1836
1837 poll_wait(file, &filter->wqh, poll_tab);
1838
1839 if (mutex_lock_interruptible(&filter->notify_lock) < 0)
1840 return EPOLLERR;
1841
1842 list_for_each_entry(cur, &filter->notif->notifications, list) {
1843 if (cur->state == SECCOMP_NOTIFY_INIT)
1844 ret |= EPOLLIN | EPOLLRDNORM;
1845 if (cur->state == SECCOMP_NOTIFY_SENT)
1846 ret |= EPOLLOUT | EPOLLWRNORM;
1847 if ((ret & EPOLLIN) && (ret & EPOLLOUT))
1848 break;
1849 }
1850
1851 mutex_unlock(&filter->notify_lock);
1852
1853 if (refcount_read(&filter->users) == 0)
1854 ret |= EPOLLHUP;
1855
1856 return ret;
1857}
1858
1859static const struct file_operations seccomp_notify_ops = {
1860 .poll = seccomp_notify_poll,
1861 .release = seccomp_notify_release,
1862 .unlocked_ioctl = seccomp_notify_ioctl,
1863 .compat_ioctl = seccomp_notify_ioctl,
1864};
1865
1866static struct file *init_listener(struct seccomp_filter *filter)
1867{
1868 struct file *ret;
1869
1870 ret = ERR_PTR(-ENOMEM);
1871 filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
1872 if (!filter->notif)
1873 goto out;
1874
1875 filter->notif->next_id = get_random_u64();
1876 INIT_LIST_HEAD(&filter->notif->notifications);
1877
1878 ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
1879 filter, O_RDWR);
1880 if (IS_ERR(ret))
1881 goto out_notif;
1882
1883 /* The file has a reference to it now */
1884 __get_seccomp_filter(filter);
1885
1886out_notif:
1887 if (IS_ERR(ret))
1888 seccomp_notify_free(filter);
1889out:
1890 return ret;
1891}
1892
1893/*
1894 * Does @new_child have a listener while an ancestor also has a listener?
1895 * If so, we'll want to reject this filter.
1896 * This only has to be tested for the current process, even in the TSYNC case,
1897 * because TSYNC installs @child with the same parent on all threads.
1898 * Note that @new_child is not hooked up to its parent at this point yet, so
1899 * we use current->seccomp.filter.
1900 */
1901static bool has_duplicate_listener(struct seccomp_filter *new_child)
1902{
1903 struct seccomp_filter *cur;
1904
1905 /* must be protected against concurrent TSYNC */
1906 lockdep_assert_held(¤t->sighand->siglock);
1907
1908 if (!new_child->notif)
1909 return false;
1910 for (cur = current->seccomp.filter; cur; cur = cur->prev) {
1911 if (cur->notif)
1912 return true;
1913 }
1914
1915 return false;
1916}
1917
1918/**
1919 * seccomp_set_mode_filter: internal function for setting seccomp filter
1920 * @flags: flags to change filter behavior
1921 * @filter: struct sock_fprog containing filter
1922 *
1923 * This function may be called repeatedly to install additional filters.
1924 * Every filter successfully installed will be evaluated (in reverse order)
1925 * for each system call the task makes.
1926 *
1927 * Once current->seccomp.mode is non-zero, it may not be changed.
1928 *
1929 * Returns 0 on success or -EINVAL on failure.
1930 */
1931static long seccomp_set_mode_filter(unsigned int flags,
1932 const char __user *filter)
1933{
1934 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
1935 struct seccomp_filter *prepared = NULL;
1936 long ret = -EINVAL;
1937 int listener = -1;
1938 struct file *listener_f = NULL;
1939
1940 /* Validate flags. */
1941 if (flags & ~SECCOMP_FILTER_FLAG_MASK)
1942 return -EINVAL;
1943
1944 /*
1945 * In the successful case, NEW_LISTENER returns the new listener fd.
1946 * But in the failure case, TSYNC returns the thread that died. If you
1947 * combine these two flags, there's no way to tell whether something
1948 * succeeded or failed. So, let's disallow this combination if the user
1949 * has not explicitly requested no errors from TSYNC.
1950 */
1951 if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
1952 (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) &&
1953 ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0))
1954 return -EINVAL;
1955
1956 /*
1957 * The SECCOMP_FILTER_FLAG_WAIT_KILLABLE_SENT flag doesn't make sense
1958 * without the SECCOMP_FILTER_FLAG_NEW_LISTENER flag.
1959 */
1960 if ((flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) &&
1961 ((flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) == 0))
1962 return -EINVAL;
1963
1964 /* Prepare the new filter before holding any locks. */
1965 prepared = seccomp_prepare_user_filter(filter);
1966 if (IS_ERR(prepared))
1967 return PTR_ERR(prepared);
1968
1969 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1970 listener = get_unused_fd_flags(O_CLOEXEC);
1971 if (listener < 0) {
1972 ret = listener;
1973 goto out_free;
1974 }
1975
1976 listener_f = init_listener(prepared);
1977 if (IS_ERR(listener_f)) {
1978 put_unused_fd(listener);
1979 ret = PTR_ERR(listener_f);
1980 goto out_free;
1981 }
1982 }
1983
1984 /*
1985 * Make sure we cannot change seccomp or nnp state via TSYNC
1986 * while another thread is in the middle of calling exec.
1987 */
1988 if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
1989 mutex_lock_killable(¤t->signal->cred_guard_mutex))
1990 goto out_put_fd;
1991
1992 spin_lock_irq(¤t->sighand->siglock);
1993
1994 if (!seccomp_may_assign_mode(seccomp_mode))
1995 goto out;
1996
1997 if (has_duplicate_listener(prepared)) {
1998 ret = -EBUSY;
1999 goto out;
2000 }
2001
2002 ret = seccomp_attach_filter(flags, prepared);
2003 if (ret)
2004 goto out;
2005 /* Do not free the successfully attached filter. */
2006 prepared = NULL;
2007
2008 seccomp_assign_mode(current, seccomp_mode, flags);
2009out:
2010 spin_unlock_irq(¤t->sighand->siglock);
2011 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
2012 mutex_unlock(¤t->signal->cred_guard_mutex);
2013out_put_fd:
2014 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
2015 if (ret) {
2016 listener_f->private_data = NULL;
2017 fput(listener_f);
2018 put_unused_fd(listener);
2019 seccomp_notify_detach(prepared);
2020 } else {
2021 fd_install(listener, listener_f);
2022 ret = listener;
2023 }
2024 }
2025out_free:
2026 seccomp_filter_free(prepared);
2027 return ret;
2028}
2029#else
2030static inline long seccomp_set_mode_filter(unsigned int flags,
2031 const char __user *filter)
2032{
2033 return -EINVAL;
2034}
2035#endif
2036
2037static long seccomp_get_action_avail(const char __user *uaction)
2038{
2039 u32 action;
2040
2041 if (copy_from_user(&action, uaction, sizeof(action)))
2042 return -EFAULT;
2043
2044 switch (action) {
2045 case SECCOMP_RET_KILL_PROCESS:
2046 case SECCOMP_RET_KILL_THREAD:
2047 case SECCOMP_RET_TRAP:
2048 case SECCOMP_RET_ERRNO:
2049 case SECCOMP_RET_USER_NOTIF:
2050 case SECCOMP_RET_TRACE:
2051 case SECCOMP_RET_LOG:
2052 case SECCOMP_RET_ALLOW:
2053 break;
2054 default:
2055 return -EOPNOTSUPP;
2056 }
2057
2058 return 0;
2059}
2060
2061static long seccomp_get_notif_sizes(void __user *usizes)
2062{
2063 struct seccomp_notif_sizes sizes = {
2064 .seccomp_notif = sizeof(struct seccomp_notif),
2065 .seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
2066 .seccomp_data = sizeof(struct seccomp_data),
2067 };
2068
2069 if (copy_to_user(usizes, &sizes, sizeof(sizes)))
2070 return -EFAULT;
2071
2072 return 0;
2073}
2074
2075/* Common entry point for both prctl and syscall. */
2076static long do_seccomp(unsigned int op, unsigned int flags,
2077 void __user *uargs)
2078{
2079 switch (op) {
2080 case SECCOMP_SET_MODE_STRICT:
2081 if (flags != 0 || uargs != NULL)
2082 return -EINVAL;
2083 return seccomp_set_mode_strict();
2084 case SECCOMP_SET_MODE_FILTER:
2085 return seccomp_set_mode_filter(flags, uargs);
2086 case SECCOMP_GET_ACTION_AVAIL:
2087 if (flags != 0)
2088 return -EINVAL;
2089
2090 return seccomp_get_action_avail(uargs);
2091 case SECCOMP_GET_NOTIF_SIZES:
2092 if (flags != 0)
2093 return -EINVAL;
2094
2095 return seccomp_get_notif_sizes(uargs);
2096 default:
2097 return -EINVAL;
2098 }
2099}
2100
2101SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
2102 void __user *, uargs)
2103{
2104 return do_seccomp(op, flags, uargs);
2105}
2106
2107/**
2108 * prctl_set_seccomp: configures current->seccomp.mode
2109 * @seccomp_mode: requested mode to use
2110 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
2111 *
2112 * Returns 0 on success or -EINVAL on failure.
2113 */
2114long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
2115{
2116 unsigned int op;
2117 void __user *uargs;
2118
2119 switch (seccomp_mode) {
2120 case SECCOMP_MODE_STRICT:
2121 op = SECCOMP_SET_MODE_STRICT;
2122 /*
2123 * Setting strict mode through prctl always ignored filter,
2124 * so make sure it is always NULL here to pass the internal
2125 * check in do_seccomp().
2126 */
2127 uargs = NULL;
2128 break;
2129 case SECCOMP_MODE_FILTER:
2130 op = SECCOMP_SET_MODE_FILTER;
2131 uargs = filter;
2132 break;
2133 default:
2134 return -EINVAL;
2135 }
2136
2137 /* prctl interface doesn't have flags, so they are always zero. */
2138 return do_seccomp(op, 0, uargs);
2139}
2140
2141#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
2142static struct seccomp_filter *get_nth_filter(struct task_struct *task,
2143 unsigned long filter_off)
2144{
2145 struct seccomp_filter *orig, *filter;
2146 unsigned long count;
2147
2148 /*
2149 * Note: this is only correct because the caller should be the (ptrace)
2150 * tracer of the task, otherwise lock_task_sighand is needed.
2151 */
2152 spin_lock_irq(&task->sighand->siglock);
2153
2154 if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
2155 spin_unlock_irq(&task->sighand->siglock);
2156 return ERR_PTR(-EINVAL);
2157 }
2158
2159 orig = task->seccomp.filter;
2160 __get_seccomp_filter(orig);
2161 spin_unlock_irq(&task->sighand->siglock);
2162
2163 count = 0;
2164 for (filter = orig; filter; filter = filter->prev)
2165 count++;
2166
2167 if (filter_off >= count) {
2168 filter = ERR_PTR(-ENOENT);
2169 goto out;
2170 }
2171
2172 count -= filter_off;
2173 for (filter = orig; filter && count > 1; filter = filter->prev)
2174 count--;
2175
2176 if (WARN_ON(count != 1 || !filter)) {
2177 filter = ERR_PTR(-ENOENT);
2178 goto out;
2179 }
2180
2181 __get_seccomp_filter(filter);
2182
2183out:
2184 __put_seccomp_filter(orig);
2185 return filter;
2186}
2187
2188long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
2189 void __user *data)
2190{
2191 struct seccomp_filter *filter;
2192 struct sock_fprog_kern *fprog;
2193 long ret;
2194
2195 if (!capable(CAP_SYS_ADMIN) ||
2196 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2197 return -EACCES;
2198 }
2199
2200 filter = get_nth_filter(task, filter_off);
2201 if (IS_ERR(filter))
2202 return PTR_ERR(filter);
2203
2204 fprog = filter->prog->orig_prog;
2205 if (!fprog) {
2206 /* This must be a new non-cBPF filter, since we save
2207 * every cBPF filter's orig_prog above when
2208 * CONFIG_CHECKPOINT_RESTORE is enabled.
2209 */
2210 ret = -EMEDIUMTYPE;
2211 goto out;
2212 }
2213
2214 ret = fprog->len;
2215 if (!data)
2216 goto out;
2217
2218 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
2219 ret = -EFAULT;
2220
2221out:
2222 __put_seccomp_filter(filter);
2223 return ret;
2224}
2225
2226long seccomp_get_metadata(struct task_struct *task,
2227 unsigned long size, void __user *data)
2228{
2229 long ret;
2230 struct seccomp_filter *filter;
2231 struct seccomp_metadata kmd = {};
2232
2233 if (!capable(CAP_SYS_ADMIN) ||
2234 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2235 return -EACCES;
2236 }
2237
2238 size = min_t(unsigned long, size, sizeof(kmd));
2239
2240 if (size < sizeof(kmd.filter_off))
2241 return -EINVAL;
2242
2243 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
2244 return -EFAULT;
2245
2246 filter = get_nth_filter(task, kmd.filter_off);
2247 if (IS_ERR(filter))
2248 return PTR_ERR(filter);
2249
2250 if (filter->log)
2251 kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
2252
2253 ret = size;
2254 if (copy_to_user(data, &kmd, size))
2255 ret = -EFAULT;
2256
2257 __put_seccomp_filter(filter);
2258 return ret;
2259}
2260#endif
2261
2262#ifdef CONFIG_SYSCTL
2263
2264/* Human readable action names for friendly sysctl interaction */
2265#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
2266#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
2267#define SECCOMP_RET_TRAP_NAME "trap"
2268#define SECCOMP_RET_ERRNO_NAME "errno"
2269#define SECCOMP_RET_USER_NOTIF_NAME "user_notif"
2270#define SECCOMP_RET_TRACE_NAME "trace"
2271#define SECCOMP_RET_LOG_NAME "log"
2272#define SECCOMP_RET_ALLOW_NAME "allow"
2273
2274static const char seccomp_actions_avail[] =
2275 SECCOMP_RET_KILL_PROCESS_NAME " "
2276 SECCOMP_RET_KILL_THREAD_NAME " "
2277 SECCOMP_RET_TRAP_NAME " "
2278 SECCOMP_RET_ERRNO_NAME " "
2279 SECCOMP_RET_USER_NOTIF_NAME " "
2280 SECCOMP_RET_TRACE_NAME " "
2281 SECCOMP_RET_LOG_NAME " "
2282 SECCOMP_RET_ALLOW_NAME;
2283
2284struct seccomp_log_name {
2285 u32 log;
2286 const char *name;
2287};
2288
2289static const struct seccomp_log_name seccomp_log_names[] = {
2290 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
2291 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
2292 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
2293 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
2294 { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
2295 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
2296 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
2297 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
2298 { }
2299};
2300
2301static bool seccomp_names_from_actions_logged(char *names, size_t size,
2302 u32 actions_logged,
2303 const char *sep)
2304{
2305 const struct seccomp_log_name *cur;
2306 bool append_sep = false;
2307
2308 for (cur = seccomp_log_names; cur->name && size; cur++) {
2309 ssize_t ret;
2310
2311 if (!(actions_logged & cur->log))
2312 continue;
2313
2314 if (append_sep) {
2315 ret = strscpy(names, sep, size);
2316 if (ret < 0)
2317 return false;
2318
2319 names += ret;
2320 size -= ret;
2321 } else
2322 append_sep = true;
2323
2324 ret = strscpy(names, cur->name, size);
2325 if (ret < 0)
2326 return false;
2327
2328 names += ret;
2329 size -= ret;
2330 }
2331
2332 return true;
2333}
2334
2335static bool seccomp_action_logged_from_name(u32 *action_logged,
2336 const char *name)
2337{
2338 const struct seccomp_log_name *cur;
2339
2340 for (cur = seccomp_log_names; cur->name; cur++) {
2341 if (!strcmp(cur->name, name)) {
2342 *action_logged = cur->log;
2343 return true;
2344 }
2345 }
2346
2347 return false;
2348}
2349
2350static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
2351{
2352 char *name;
2353
2354 *actions_logged = 0;
2355 while ((name = strsep(&names, " ")) && *name) {
2356 u32 action_logged = 0;
2357
2358 if (!seccomp_action_logged_from_name(&action_logged, name))
2359 return false;
2360
2361 *actions_logged |= action_logged;
2362 }
2363
2364 return true;
2365}
2366
2367static int read_actions_logged(const struct ctl_table *ro_table, void *buffer,
2368 size_t *lenp, loff_t *ppos)
2369{
2370 char names[sizeof(seccomp_actions_avail)];
2371 struct ctl_table table;
2372
2373 memset(names, 0, sizeof(names));
2374
2375 if (!seccomp_names_from_actions_logged(names, sizeof(names),
2376 seccomp_actions_logged, " "))
2377 return -EINVAL;
2378
2379 table = *ro_table;
2380 table.data = names;
2381 table.maxlen = sizeof(names);
2382 return proc_dostring(&table, 0, buffer, lenp, ppos);
2383}
2384
2385static int write_actions_logged(const struct ctl_table *ro_table, void *buffer,
2386 size_t *lenp, loff_t *ppos, u32 *actions_logged)
2387{
2388 char names[sizeof(seccomp_actions_avail)];
2389 struct ctl_table table;
2390 int ret;
2391
2392 if (!capable(CAP_SYS_ADMIN))
2393 return -EPERM;
2394
2395 memset(names, 0, sizeof(names));
2396
2397 table = *ro_table;
2398 table.data = names;
2399 table.maxlen = sizeof(names);
2400 ret = proc_dostring(&table, 1, buffer, lenp, ppos);
2401 if (ret)
2402 return ret;
2403
2404 if (!seccomp_actions_logged_from_names(actions_logged, table.data))
2405 return -EINVAL;
2406
2407 if (*actions_logged & SECCOMP_LOG_ALLOW)
2408 return -EINVAL;
2409
2410 seccomp_actions_logged = *actions_logged;
2411 return 0;
2412}
2413
2414static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
2415 int ret)
2416{
2417 char names[sizeof(seccomp_actions_avail)];
2418 char old_names[sizeof(seccomp_actions_avail)];
2419 const char *new = names;
2420 const char *old = old_names;
2421
2422 if (!audit_enabled)
2423 return;
2424
2425 memset(names, 0, sizeof(names));
2426 memset(old_names, 0, sizeof(old_names));
2427
2428 if (ret)
2429 new = "?";
2430 else if (!actions_logged)
2431 new = "(none)";
2432 else if (!seccomp_names_from_actions_logged(names, sizeof(names),
2433 actions_logged, ","))
2434 new = "?";
2435
2436 if (!old_actions_logged)
2437 old = "(none)";
2438 else if (!seccomp_names_from_actions_logged(old_names,
2439 sizeof(old_names),
2440 old_actions_logged, ","))
2441 old = "?";
2442
2443 return audit_seccomp_actions_logged(new, old, !ret);
2444}
2445
2446static int seccomp_actions_logged_handler(const struct ctl_table *ro_table, int write,
2447 void *buffer, size_t *lenp,
2448 loff_t *ppos)
2449{
2450 int ret;
2451
2452 if (write) {
2453 u32 actions_logged = 0;
2454 u32 old_actions_logged = seccomp_actions_logged;
2455
2456 ret = write_actions_logged(ro_table, buffer, lenp, ppos,
2457 &actions_logged);
2458 audit_actions_logged(actions_logged, old_actions_logged, ret);
2459 } else
2460 ret = read_actions_logged(ro_table, buffer, lenp, ppos);
2461
2462 return ret;
2463}
2464
2465static struct ctl_table seccomp_sysctl_table[] = {
2466 {
2467 .procname = "actions_avail",
2468 .data = (void *) &seccomp_actions_avail,
2469 .maxlen = sizeof(seccomp_actions_avail),
2470 .mode = 0444,
2471 .proc_handler = proc_dostring,
2472 },
2473 {
2474 .procname = "actions_logged",
2475 .mode = 0644,
2476 .proc_handler = seccomp_actions_logged_handler,
2477 },
2478};
2479
2480static int __init seccomp_sysctl_init(void)
2481{
2482 register_sysctl_init("kernel/seccomp", seccomp_sysctl_table);
2483 return 0;
2484}
2485
2486device_initcall(seccomp_sysctl_init)
2487
2488#endif /* CONFIG_SYSCTL */
2489
2490#ifdef CONFIG_SECCOMP_CACHE_DEBUG
2491/* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */
2492static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name,
2493 const void *bitmap, size_t bitmap_size)
2494{
2495 int nr;
2496
2497 for (nr = 0; nr < bitmap_size; nr++) {
2498 bool cached = test_bit(nr, bitmap);
2499 char *status = cached ? "ALLOW" : "FILTER";
2500
2501 seq_printf(m, "%s %d %s\n", name, nr, status);
2502 }
2503}
2504
2505int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns,
2506 struct pid *pid, struct task_struct *task)
2507{
2508 struct seccomp_filter *f;
2509 unsigned long flags;
2510
2511 /*
2512 * We don't want some sandboxed process to know what their seccomp
2513 * filters consist of.
2514 */
2515 if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
2516 return -EACCES;
2517
2518 if (!lock_task_sighand(task, &flags))
2519 return -ESRCH;
2520
2521 f = READ_ONCE(task->seccomp.filter);
2522 if (!f) {
2523 unlock_task_sighand(task, &flags);
2524 return 0;
2525 }
2526
2527 /* prevent filter from being freed while we are printing it */
2528 __get_seccomp_filter(f);
2529 unlock_task_sighand(task, &flags);
2530
2531 proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME,
2532 f->cache.allow_native,
2533 SECCOMP_ARCH_NATIVE_NR);
2534
2535#ifdef SECCOMP_ARCH_COMPAT
2536 proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME,
2537 f->cache.allow_compat,
2538 SECCOMP_ARCH_COMPAT_NR);
2539#endif /* SECCOMP_ARCH_COMPAT */
2540
2541 __put_seccomp_filter(f);
2542 return 0;
2543}
2544#endif /* CONFIG_SECCOMP_CACHE_DEBUG */