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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 */
64 struct 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 */
78 static 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 */
108 static 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)))
188 static 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
222 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
223 {
224 assert_spin_locked(&current->sighand->siglock);
225
226 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
227 return false;
228
229 return true;
230 }
231
232 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
233
234 static 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. */
254 static 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 */
275 static inline pid_t seccomp_can_sync_threads(void)
276 {
277 struct task_struct *thread, *caller;
278
279 BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
280 assert_spin_locked(&current->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 */
316 static inline void seccomp_sync_threads(unsigned long flags)
317 {
318 struct task_struct *thread, *caller;
319
320 BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
321 assert_spin_locked(&current->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 */
368 static 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 */
413 static struct seccomp_filter *
414 seccomp_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);
431 out:
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 */
444 static 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(&current->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
486 static 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 */
493 void 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
501 static 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
509 static 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 */
520 void put_seccomp_filter(struct task_struct *tsk)
521 {
522 __put_seccomp_filter(tsk->seccomp.filter);
523 }
524
525 static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
526 {
527 memset(info, 0, sizeof(*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 */
543 static 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
560 static 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
567 static 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 */
615 static const int mode1_syscalls[] = {
616 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
617 0, /* null terminated */
618 };
619
620 static 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
640 void 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
658 static 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
769 skip:
770 seccomp_log(this_syscall, 0, action, match ? match->log : false);
771 return -1;
772 }
773 #else
774 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
775 const bool recheck_after_trace)
776 {
777 BUG();
778 }
779 #endif
780
781 int __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
805 long 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 */
817 static 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(&current->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
833 out:
834 spin_unlock_irq(&current->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 */
853 static 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(&current->signal->cred_guard_mutex))
875 goto out_free;
876
877 spin_lock_irq(&current->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);
889 out:
890 spin_unlock_irq(&current->sighand->siglock);
891 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
892 mutex_unlock(&current->signal->cred_guard_mutex);
893 out_free:
894 seccomp_filter_free(prepared);
895 return ret;
896 }
897 #else
898 static inline long seccomp_set_mode_filter(unsigned int flags,
899 const char __user *filter)
900 {
901 return -EINVAL;
902 }
903 #endif
904
905 static 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. */
929 static 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
949 SYSCALL_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 */
962 long 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)
990 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
991 void __user *data)
992 {
993 struct seccomp_filter *filter;
994 struct sock_fprog_kern *fprog;
995 long ret;
996 unsigned long count = 0;
997
998 if (!capable(CAP_SYS_ADMIN) ||
999 current->seccomp.mode != SECCOMP_MODE_DISABLED) {
1000 return -EACCES;
1001 }
1002
1003 spin_lock_irq(&task->sighand->siglock);
1004 if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
1005 ret = -EINVAL;
1006 goto out;
1007 }
1008
1009 filter = task->seccomp.filter;
1010 while (filter) {
1011 filter = filter->prev;
1012 count++;
1013 }
1014
1015 if (filter_off >= count) {
1016 ret = -ENOENT;
1017 goto out;
1018 }
1019 count -= filter_off;
1020
1021 filter = task->seccomp.filter;
1022 while (filter && count > 1) {
1023 filter = filter->prev;
1024 count--;
1025 }
1026
1027 if (WARN_ON(count != 1 || !filter)) {
1028 /* The filter tree shouldn't shrink while we're using it. */
1029 ret = -ENOENT;
1030 goto out;
1031 }
1032
1033 fprog = filter->prog->orig_prog;
1034 if (!fprog) {
1035 /* This must be a new non-cBPF filter, since we save
1036 * every cBPF filter's orig_prog above when
1037 * CONFIG_CHECKPOINT_RESTORE is enabled.
1038 */
1039 ret = -EMEDIUMTYPE;
1040 goto out;
1041 }
1042
1043 ret = fprog->len;
1044 if (!data)
1045 goto out;
1046
1047 __get_seccomp_filter(filter);
1048 spin_unlock_irq(&task->sighand->siglock);
1049
1050 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
1051 ret = -EFAULT;
1052
1053 __put_seccomp_filter(filter);
1054 return ret;
1055
1056 out:
1057 spin_unlock_irq(&task->sighand->siglock);
1058 return ret;
1059 }
1060 #endif
1061
1062 #ifdef CONFIG_SYSCTL
1063
1064 /* Human readable action names for friendly sysctl interaction */
1065 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
1066 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
1067 #define SECCOMP_RET_TRAP_NAME "trap"
1068 #define SECCOMP_RET_ERRNO_NAME "errno"
1069 #define SECCOMP_RET_TRACE_NAME "trace"
1070 #define SECCOMP_RET_LOG_NAME "log"
1071 #define SECCOMP_RET_ALLOW_NAME "allow"
1072
1073 static const char seccomp_actions_avail[] =
1074 SECCOMP_RET_KILL_PROCESS_NAME " "
1075 SECCOMP_RET_KILL_THREAD_NAME " "
1076 SECCOMP_RET_TRAP_NAME " "
1077 SECCOMP_RET_ERRNO_NAME " "
1078 SECCOMP_RET_TRACE_NAME " "
1079 SECCOMP_RET_LOG_NAME " "
1080 SECCOMP_RET_ALLOW_NAME;
1081
1082 struct seccomp_log_name {
1083 u32 log;
1084 const char *name;
1085 };
1086
1087 static const struct seccomp_log_name seccomp_log_names[] = {
1088 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
1089 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
1090 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
1091 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
1092 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
1093 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
1094 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
1095 { }
1096 };
1097
1098 static bool seccomp_names_from_actions_logged(char *names, size_t size,
1099 u32 actions_logged)
1100 {
1101 const struct seccomp_log_name *cur;
1102 bool append_space = false;
1103
1104 for (cur = seccomp_log_names; cur->name && size; cur++) {
1105 ssize_t ret;
1106
1107 if (!(actions_logged & cur->log))
1108 continue;
1109
1110 if (append_space) {
1111 ret = strscpy(names, " ", size);
1112 if (ret < 0)
1113 return false;
1114
1115 names += ret;
1116 size -= ret;
1117 } else
1118 append_space = true;
1119
1120 ret = strscpy(names, cur->name, size);
1121 if (ret < 0)
1122 return false;
1123
1124 names += ret;
1125 size -= ret;
1126 }
1127
1128 return true;
1129 }
1130
1131 static bool seccomp_action_logged_from_name(u32 *action_logged,
1132 const char *name)
1133 {
1134 const struct seccomp_log_name *cur;
1135
1136 for (cur = seccomp_log_names; cur->name; cur++) {
1137 if (!strcmp(cur->name, name)) {
1138 *action_logged = cur->log;
1139 return true;
1140 }
1141 }
1142
1143 return false;
1144 }
1145
1146 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
1147 {
1148 char *name;
1149
1150 *actions_logged = 0;
1151 while ((name = strsep(&names, " ")) && *name) {
1152 u32 action_logged = 0;
1153
1154 if (!seccomp_action_logged_from_name(&action_logged, name))
1155 return false;
1156
1157 *actions_logged |= action_logged;
1158 }
1159
1160 return true;
1161 }
1162
1163 static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
1164 void __user *buffer, size_t *lenp,
1165 loff_t *ppos)
1166 {
1167 char names[sizeof(seccomp_actions_avail)];
1168 struct ctl_table table;
1169 int ret;
1170
1171 if (write && !capable(CAP_SYS_ADMIN))
1172 return -EPERM;
1173
1174 memset(names, 0, sizeof(names));
1175
1176 if (!write) {
1177 if (!seccomp_names_from_actions_logged(names, sizeof(names),
1178 seccomp_actions_logged))
1179 return -EINVAL;
1180 }
1181
1182 table = *ro_table;
1183 table.data = names;
1184 table.maxlen = sizeof(names);
1185 ret = proc_dostring(&table, write, buffer, lenp, ppos);
1186 if (ret)
1187 return ret;
1188
1189 if (write) {
1190 u32 actions_logged;
1191
1192 if (!seccomp_actions_logged_from_names(&actions_logged,
1193 table.data))
1194 return -EINVAL;
1195
1196 if (actions_logged & SECCOMP_LOG_ALLOW)
1197 return -EINVAL;
1198
1199 seccomp_actions_logged = actions_logged;
1200 }
1201
1202 return 0;
1203 }
1204
1205 static struct ctl_path seccomp_sysctl_path[] = {
1206 { .procname = "kernel", },
1207 { .procname = "seccomp", },
1208 { }
1209 };
1210
1211 static struct ctl_table seccomp_sysctl_table[] = {
1212 {
1213 .procname = "actions_avail",
1214 .data = (void *) &seccomp_actions_avail,
1215 .maxlen = sizeof(seccomp_actions_avail),
1216 .mode = 0444,
1217 .proc_handler = proc_dostring,
1218 },
1219 {
1220 .procname = "actions_logged",
1221 .mode = 0644,
1222 .proc_handler = seccomp_actions_logged_handler,
1223 },
1224 { }
1225 };
1226
1227 static int __init seccomp_sysctl_init(void)
1228 {
1229 struct ctl_table_header *hdr;
1230
1231 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
1232 if (!hdr)
1233 pr_warn("seccomp: sysctl registration failed\n");
1234 else
1235 kmemleak_not_leak(hdr);
1236
1237 return 0;
1238 }
1239
1240 device_initcall(seccomp_sysctl_init)
1241
1242 #endif /* CONFIG_SYSCTL */