projects/linux·blob v4.0-rc6 · refs

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1/*
2 * linux/kernel/seccomp.c
3 *
4 * Copyright 2004-2005 Andrea Arcangeli <[email protected]>
5 *
6 * Copyright (C) 2012 Google, Inc.
7 * Will Drewry <[email protected]>
8 *
9 * This defines a simple but solid secure-computing facility.
10 *
11 * Mode 1 uses a fixed list of allowed system calls.
12 * Mode 2 allows user-defined system call filters in the form
13 * of Berkeley Packet Filters/Linux Socket Filters.
14 */
15
16#include <linux/atomic.h>
17#include <linux/audit.h>
18#include <linux/compat.h>
19#include <linux/sched.h>
20#include <linux/seccomp.h>
21#include <linux/slab.h>
22#include <linux/syscalls.h>
23
24#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
25#include <asm/syscall.h>
26#endif
27
28#ifdef CONFIG_SECCOMP_FILTER
29#include <linux/filter.h>
30#include <linux/pid.h>
31#include <linux/ptrace.h>
32#include <linux/security.h>
33#include <linux/tracehook.h>
34#include <linux/uaccess.h>
35
36/**
37 * struct seccomp_filter - container for seccomp BPF programs
38 *
39 * @usage: reference count to manage the object lifetime.
40 * get/put helpers should be used when accessing an instance
41 * outside of a lifetime-guarded section. In general, this
42 * is only needed for handling filters shared across tasks.
43 * @prev: points to a previously installed, or inherited, filter
44 * @len: the number of instructions in the program
45 * @insnsi: the BPF program instructions to evaluate
46 *
47 * seccomp_filter objects are organized in a tree linked via the @prev
48 * pointer. For any task, it appears to be a singly-linked list starting
49 * with current->seccomp.filter, the most recently attached or inherited filter.
50 * However, multiple filters may share a @prev node, by way of fork(), which
51 * results in a unidirectional tree existing in memory. This is similar to
52 * how namespaces work.
53 *
54 * seccomp_filter objects should never be modified after being attached
55 * to a task_struct (other than @usage).
56 */
57struct seccomp_filter {
58 atomic_t usage;
59 struct seccomp_filter *prev;
60 struct bpf_prog *prog;
61};
62
63/* Limit any path through the tree to 256KB worth of instructions. */
64#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
65
66/*
67 * Endianness is explicitly ignored and left for BPF program authors to manage
68 * as per the specific architecture.
69 */
70static void populate_seccomp_data(struct seccomp_data *sd)
71{
72 struct task_struct *task = current;
73 struct pt_regs *regs = task_pt_regs(task);
74 unsigned long args[6];
75
76 sd->nr = syscall_get_nr(task, regs);
77 sd->arch = syscall_get_arch();
78 syscall_get_arguments(task, regs, 0, 6, args);
79 sd->args[0] = args[0];
80 sd->args[1] = args[1];
81 sd->args[2] = args[2];
82 sd->args[3] = args[3];
83 sd->args[4] = args[4];
84 sd->args[5] = args[5];
85 sd->instruction_pointer = KSTK_EIP(task);
86}
87
88/**
89 * seccomp_check_filter - verify seccomp filter code
90 * @filter: filter to verify
91 * @flen: length of filter
92 *
93 * Takes a previously checked filter (by bpf_check_classic) and
94 * redirects all filter code that loads struct sk_buff data
95 * and related data through seccomp_bpf_load. It also
96 * enforces length and alignment checking of those loads.
97 *
98 * Returns 0 if the rule set is legal or -EINVAL if not.
99 */
100static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
101{
102 int pc;
103 for (pc = 0; pc < flen; pc++) {
104 struct sock_filter *ftest = &filter[pc];
105 u16 code = ftest->code;
106 u32 k = ftest->k;
107
108 switch (code) {
109 case BPF_LD | BPF_W | BPF_ABS:
110 ftest->code = BPF_LDX | BPF_W | BPF_ABS;
111 /* 32-bit aligned and not out of bounds. */
112 if (k >= sizeof(struct seccomp_data) || k & 3)
113 return -EINVAL;
114 continue;
115 case BPF_LD | BPF_W | BPF_LEN:
116 ftest->code = BPF_LD | BPF_IMM;
117 ftest->k = sizeof(struct seccomp_data);
118 continue;
119 case BPF_LDX | BPF_W | BPF_LEN:
120 ftest->code = BPF_LDX | BPF_IMM;
121 ftest->k = sizeof(struct seccomp_data);
122 continue;
123 /* Explicitly include allowed calls. */
124 case BPF_RET | BPF_K:
125 case BPF_RET | BPF_A:
126 case BPF_ALU | BPF_ADD | BPF_K:
127 case BPF_ALU | BPF_ADD | BPF_X:
128 case BPF_ALU | BPF_SUB | BPF_K:
129 case BPF_ALU | BPF_SUB | BPF_X:
130 case BPF_ALU | BPF_MUL | BPF_K:
131 case BPF_ALU | BPF_MUL | BPF_X:
132 case BPF_ALU | BPF_DIV | BPF_K:
133 case BPF_ALU | BPF_DIV | BPF_X:
134 case BPF_ALU | BPF_AND | BPF_K:
135 case BPF_ALU | BPF_AND | BPF_X:
136 case BPF_ALU | BPF_OR | BPF_K:
137 case BPF_ALU | BPF_OR | BPF_X:
138 case BPF_ALU | BPF_XOR | BPF_K:
139 case BPF_ALU | BPF_XOR | BPF_X:
140 case BPF_ALU | BPF_LSH | BPF_K:
141 case BPF_ALU | BPF_LSH | BPF_X:
142 case BPF_ALU | BPF_RSH | BPF_K:
143 case BPF_ALU | BPF_RSH | BPF_X:
144 case BPF_ALU | BPF_NEG:
145 case BPF_LD | BPF_IMM:
146 case BPF_LDX | BPF_IMM:
147 case BPF_MISC | BPF_TAX:
148 case BPF_MISC | BPF_TXA:
149 case BPF_LD | BPF_MEM:
150 case BPF_LDX | BPF_MEM:
151 case BPF_ST:
152 case BPF_STX:
153 case BPF_JMP | BPF_JA:
154 case BPF_JMP | BPF_JEQ | BPF_K:
155 case BPF_JMP | BPF_JEQ | BPF_X:
156 case BPF_JMP | BPF_JGE | BPF_K:
157 case BPF_JMP | BPF_JGE | BPF_X:
158 case BPF_JMP | BPF_JGT | BPF_K:
159 case BPF_JMP | BPF_JGT | BPF_X:
160 case BPF_JMP | BPF_JSET | BPF_K:
161 case BPF_JMP | BPF_JSET | BPF_X:
162 continue;
163 default:
164 return -EINVAL;
165 }
166 }
167 return 0;
168}
169
170/**
171 * seccomp_run_filters - evaluates all seccomp filters against @syscall
172 * @syscall: number of the current system call
173 *
174 * Returns valid seccomp BPF response codes.
175 */
176static u32 seccomp_run_filters(struct seccomp_data *sd)
177{
178 struct seccomp_filter *f = ACCESS_ONCE(current->seccomp.filter);
179 struct seccomp_data sd_local;
180 u32 ret = SECCOMP_RET_ALLOW;
181
182 /* Ensure unexpected behavior doesn't result in failing open. */
183 if (unlikely(WARN_ON(f == NULL)))
184 return SECCOMP_RET_KILL;
185
186 /* Make sure cross-thread synced filter points somewhere sane. */
187 smp_read_barrier_depends();
188
189 if (!sd) {
190 populate_seccomp_data(&sd_local);
191 sd = &sd_local;
192 }
193
194 /*
195 * All filters in the list are evaluated and the lowest BPF return
196 * value always takes priority (ignoring the DATA).
197 */
198 for (; f; f = f->prev) {
199 u32 cur_ret = BPF_PROG_RUN(f->prog, (void *)sd);
200
201 if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
202 ret = cur_ret;
203 }
204 return ret;
205}
206#endif /* CONFIG_SECCOMP_FILTER */
207
208static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
209{
210 assert_spin_locked(&current->sighand->siglock);
211
212 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
213 return false;
214
215 return true;
216}
217
218static inline void seccomp_assign_mode(struct task_struct *task,
219 unsigned long seccomp_mode)
220{
221 assert_spin_locked(&task->sighand->siglock);
222
223 task->seccomp.mode = seccomp_mode;
224 /*
225 * Make sure TIF_SECCOMP cannot be set before the mode (and
226 * filter) is set.
227 */
228 smp_mb__before_atomic();
229 set_tsk_thread_flag(task, TIF_SECCOMP);
230}
231
232#ifdef CONFIG_SECCOMP_FILTER
233/* Returns 1 if the parent is an ancestor of the child. */
234static int is_ancestor(struct seccomp_filter *parent,
235 struct seccomp_filter *child)
236{
237 /* NULL is the root ancestor. */
238 if (parent == NULL)
239 return 1;
240 for (; child; child = child->prev)
241 if (child == parent)
242 return 1;
243 return 0;
244}
245
246/**
247 * seccomp_can_sync_threads: checks if all threads can be synchronized
248 *
249 * Expects sighand and cred_guard_mutex locks to be held.
250 *
251 * Returns 0 on success, -ve on error, or the pid of a thread which was
252 * either not in the correct seccomp mode or it did not have an ancestral
253 * seccomp filter.
254 */
255static inline pid_t seccomp_can_sync_threads(void)
256{
257 struct task_struct *thread, *caller;
258
259 BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
260 assert_spin_locked(&current->sighand->siglock);
261
262 /* Validate all threads being eligible for synchronization. */
263 caller = current;
264 for_each_thread(caller, thread) {
265 pid_t failed;
266
267 /* Skip current, since it is initiating the sync. */
268 if (thread == caller)
269 continue;
270
271 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
272 (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
273 is_ancestor(thread->seccomp.filter,
274 caller->seccomp.filter)))
275 continue;
276
277 /* Return the first thread that cannot be synchronized. */
278 failed = task_pid_vnr(thread);
279 /* If the pid cannot be resolved, then return -ESRCH */
280 if (unlikely(WARN_ON(failed == 0)))
281 failed = -ESRCH;
282 return failed;
283 }
284
285 return 0;
286}
287
288/**
289 * seccomp_sync_threads: sets all threads to use current's filter
290 *
291 * Expects sighand and cred_guard_mutex locks to be held, and for
292 * seccomp_can_sync_threads() to have returned success already
293 * without dropping the locks.
294 *
295 */
296static inline void seccomp_sync_threads(void)
297{
298 struct task_struct *thread, *caller;
299
300 BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
301 assert_spin_locked(&current->sighand->siglock);
302
303 /* Synchronize all threads. */
304 caller = current;
305 for_each_thread(caller, thread) {
306 /* Skip current, since it needs no changes. */
307 if (thread == caller)
308 continue;
309
310 /* Get a task reference for the new leaf node. */
311 get_seccomp_filter(caller);
312 /*
313 * Drop the task reference to the shared ancestor since
314 * current's path will hold a reference. (This also
315 * allows a put before the assignment.)
316 */
317 put_seccomp_filter(thread);
318 smp_store_release(&thread->seccomp.filter,
319 caller->seccomp.filter);
320 /*
321 * Opt the other thread into seccomp if needed.
322 * As threads are considered to be trust-realm
323 * equivalent (see ptrace_may_access), it is safe to
324 * allow one thread to transition the other.
325 */
326 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) {
327 /*
328 * Don't let an unprivileged task work around
329 * the no_new_privs restriction by creating
330 * a thread that sets it up, enters seccomp,
331 * then dies.
332 */
333 if (task_no_new_privs(caller))
334 task_set_no_new_privs(thread);
335
336 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
337 }
338 }
339}
340
341/**
342 * seccomp_prepare_filter: Prepares a seccomp filter for use.
343 * @fprog: BPF program to install
344 *
345 * Returns filter on success or an ERR_PTR on failure.
346 */
347static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
348{
349 struct seccomp_filter *filter;
350 unsigned long fp_size;
351 struct sock_filter *fp;
352 int new_len;
353 long ret;
354
355 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
356 return ERR_PTR(-EINVAL);
357 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
358 fp_size = fprog->len * sizeof(struct sock_filter);
359
360 /*
361 * Installing a seccomp filter requires that the task has
362 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
363 * This avoids scenarios where unprivileged tasks can affect the
364 * behavior of privileged children.
365 */
366 if (!task_no_new_privs(current) &&
367 security_capable_noaudit(current_cred(), current_user_ns(),
368 CAP_SYS_ADMIN) != 0)
369 return ERR_PTR(-EACCES);
370
371 fp = kzalloc(fp_size, GFP_KERNEL|__GFP_NOWARN);
372 if (!fp)
373 return ERR_PTR(-ENOMEM);
374
375 /* Copy the instructions from fprog. */
376 ret = -EFAULT;
377 if (copy_from_user(fp, fprog->filter, fp_size))
378 goto free_prog;
379
380 /* Check and rewrite the fprog via the skb checker */
381 ret = bpf_check_classic(fp, fprog->len);
382 if (ret)
383 goto free_prog;
384
385 /* Check and rewrite the fprog for seccomp use */
386 ret = seccomp_check_filter(fp, fprog->len);
387 if (ret)
388 goto free_prog;
389
390 /* Convert 'sock_filter' insns to 'bpf_insn' insns */
391 ret = bpf_convert_filter(fp, fprog->len, NULL, &new_len);
392 if (ret)
393 goto free_prog;
394
395 /* Allocate a new seccomp_filter */
396 ret = -ENOMEM;
397 filter = kzalloc(sizeof(struct seccomp_filter),
398 GFP_KERNEL|__GFP_NOWARN);
399 if (!filter)
400 goto free_prog;
401
402 filter->prog = bpf_prog_alloc(bpf_prog_size(new_len), __GFP_NOWARN);
403 if (!filter->prog)
404 goto free_filter;
405
406 ret = bpf_convert_filter(fp, fprog->len, filter->prog->insnsi, &new_len);
407 if (ret)
408 goto free_filter_prog;
409
410 kfree(fp);
411 atomic_set(&filter->usage, 1);
412 filter->prog->len = new_len;
413
414 bpf_prog_select_runtime(filter->prog);
415
416 return filter;
417
418free_filter_prog:
419 __bpf_prog_free(filter->prog);
420free_filter:
421 kfree(filter);
422free_prog:
423 kfree(fp);
424 return ERR_PTR(ret);
425}
426
427/**
428 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
429 * @user_filter: pointer to the user data containing a sock_fprog.
430 *
431 * Returns 0 on success and non-zero otherwise.
432 */
433static struct seccomp_filter *
434seccomp_prepare_user_filter(const char __user *user_filter)
435{
436 struct sock_fprog fprog;
437 struct seccomp_filter *filter = ERR_PTR(-EFAULT);
438
439#ifdef CONFIG_COMPAT
440 if (is_compat_task()) {
441 struct compat_sock_fprog fprog32;
442 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
443 goto out;
444 fprog.len = fprog32.len;
445 fprog.filter = compat_ptr(fprog32.filter);
446 } else /* falls through to the if below. */
447#endif
448 if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
449 goto out;
450 filter = seccomp_prepare_filter(&fprog);
451out:
452 return filter;
453}
454
455/**
456 * seccomp_attach_filter: validate and attach filter
457 * @flags: flags to change filter behavior
458 * @filter: seccomp filter to add to the current process
459 *
460 * Caller must be holding current->sighand->siglock lock.
461 *
462 * Returns 0 on success, -ve on error.
463 */
464static long seccomp_attach_filter(unsigned int flags,
465 struct seccomp_filter *filter)
466{
467 unsigned long total_insns;
468 struct seccomp_filter *walker;
469
470 assert_spin_locked(&current->sighand->siglock);
471
472 /* Validate resulting filter length. */
473 total_insns = filter->prog->len;
474 for (walker = current->seccomp.filter; walker; walker = walker->prev)
475 total_insns += walker->prog->len + 4; /* 4 instr penalty */
476 if (total_insns > MAX_INSNS_PER_PATH)
477 return -ENOMEM;
478
479 /* If thread sync has been requested, check that it is possible. */
480 if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
481 int ret;
482
483 ret = seccomp_can_sync_threads();
484 if (ret)
485 return ret;
486 }
487
488 /*
489 * If there is an existing filter, make it the prev and don't drop its
490 * task reference.
491 */
492 filter->prev = current->seccomp.filter;
493 current->seccomp.filter = filter;
494
495 /* Now that the new filter is in place, synchronize to all threads. */
496 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
497 seccomp_sync_threads();
498
499 return 0;
500}
501
502/* get_seccomp_filter - increments the reference count of the filter on @tsk */
503void get_seccomp_filter(struct task_struct *tsk)
504{
505 struct seccomp_filter *orig = tsk->seccomp.filter;
506 if (!orig)
507 return;
508 /* Reference count is bounded by the number of total processes. */
509 atomic_inc(&orig->usage);
510}
511
512static inline void seccomp_filter_free(struct seccomp_filter *filter)
513{
514 if (filter) {
515 bpf_prog_free(filter->prog);
516 kfree(filter);
517 }
518}
519
520/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
521void put_seccomp_filter(struct task_struct *tsk)
522{
523 struct seccomp_filter *orig = tsk->seccomp.filter;
524 /* Clean up single-reference branches iteratively. */
525 while (orig && atomic_dec_and_test(&orig->usage)) {
526 struct seccomp_filter *freeme = orig;
527 orig = orig->prev;
528 seccomp_filter_free(freeme);
529 }
530}
531
532/**
533 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
534 * @syscall: syscall number to send to userland
535 * @reason: filter-supplied reason code to send to userland (via si_errno)
536 *
537 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
538 */
539static void seccomp_send_sigsys(int syscall, int reason)
540{
541 struct siginfo info;
542 memset(&info, 0, sizeof(info));
543 info.si_signo = SIGSYS;
544 info.si_code = SYS_SECCOMP;
545 info.si_call_addr = (void __user *)KSTK_EIP(current);
546 info.si_errno = reason;
547 info.si_arch = syscall_get_arch();
548 info.si_syscall = syscall;
549 force_sig_info(SIGSYS, &info, current);
550}
551#endif /* CONFIG_SECCOMP_FILTER */
552
553/*
554 * Secure computing mode 1 allows only read/write/exit/sigreturn.
555 * To be fully secure this must be combined with rlimit
556 * to limit the stack allocations too.
557 */
558static int mode1_syscalls[] = {
559 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
560 0, /* null terminated */
561};
562
563#ifdef CONFIG_COMPAT
564static int mode1_syscalls_32[] = {
565 __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
566 0, /* null terminated */
567};
568#endif
569
570static void __secure_computing_strict(int this_syscall)
571{
572 int *syscall_whitelist = mode1_syscalls;
573#ifdef CONFIG_COMPAT
574 if (is_compat_task())
575 syscall_whitelist = mode1_syscalls_32;
576#endif
577 do {
578 if (*syscall_whitelist == this_syscall)
579 return;
580 } while (*++syscall_whitelist);
581
582#ifdef SECCOMP_DEBUG
583 dump_stack();
584#endif
585 audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL);
586 do_exit(SIGKILL);
587}
588
589#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
590void secure_computing_strict(int this_syscall)
591{
592 int mode = current->seccomp.mode;
593
594 if (mode == 0)
595 return;
596 else if (mode == SECCOMP_MODE_STRICT)
597 __secure_computing_strict(this_syscall);
598 else
599 BUG();
600}
601#else
602int __secure_computing(void)
603{
604 u32 phase1_result = seccomp_phase1(NULL);
605
606 if (likely(phase1_result == SECCOMP_PHASE1_OK))
607 return 0;
608 else if (likely(phase1_result == SECCOMP_PHASE1_SKIP))
609 return -1;
610 else
611 return seccomp_phase2(phase1_result);
612}
613
614#ifdef CONFIG_SECCOMP_FILTER
615static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
616{
617 u32 filter_ret, action;
618 int data;
619
620 /*
621 * Make sure that any changes to mode from another thread have
622 * been seen after TIF_SECCOMP was seen.
623 */
624 rmb();
625
626 filter_ret = seccomp_run_filters(sd);
627 data = filter_ret & SECCOMP_RET_DATA;
628 action = filter_ret & SECCOMP_RET_ACTION;
629
630 switch (action) {
631 case SECCOMP_RET_ERRNO:
632 /* Set low-order bits as an errno, capped at MAX_ERRNO. */
633 if (data > MAX_ERRNO)
634 data = MAX_ERRNO;
635 syscall_set_return_value(current, task_pt_regs(current),
636 -data, 0);
637 goto skip;
638
639 case SECCOMP_RET_TRAP:
640 /* Show the handler the original registers. */
641 syscall_rollback(current, task_pt_regs(current));
642 /* Let the filter pass back 16 bits of data. */
643 seccomp_send_sigsys(this_syscall, data);
644 goto skip;
645
646 case SECCOMP_RET_TRACE:
647 return filter_ret; /* Save the rest for phase 2. */
648
649 case SECCOMP_RET_ALLOW:
650 return SECCOMP_PHASE1_OK;
651
652 case SECCOMP_RET_KILL:
653 default:
654 audit_seccomp(this_syscall, SIGSYS, action);
655 do_exit(SIGSYS);
656 }
657
658 unreachable();
659
660skip:
661 audit_seccomp(this_syscall, 0, action);
662 return SECCOMP_PHASE1_SKIP;
663}
664#endif
665
666/**
667 * seccomp_phase1() - run fast path seccomp checks on the current syscall
668 * @arg sd: The seccomp_data or NULL
669 *
670 * This only reads pt_regs via the syscall_xyz helpers. The only change
671 * it will make to pt_regs is via syscall_set_return_value, and it will
672 * only do that if it returns SECCOMP_PHASE1_SKIP.
673 *
674 * If sd is provided, it will not read pt_regs at all.
675 *
676 * It may also call do_exit or force a signal; these actions must be
677 * safe.
678 *
679 * If it returns SECCOMP_PHASE1_OK, the syscall passes checks and should
680 * be processed normally.
681 *
682 * If it returns SECCOMP_PHASE1_SKIP, then the syscall should not be
683 * invoked. In this case, seccomp_phase1 will have set the return value
684 * using syscall_set_return_value.
685 *
686 * If it returns anything else, then the return value should be passed
687 * to seccomp_phase2 from a context in which ptrace hooks are safe.
688 */
689u32 seccomp_phase1(struct seccomp_data *sd)
690{
691 int mode = current->seccomp.mode;
692 int this_syscall = sd ? sd->nr :
693 syscall_get_nr(current, task_pt_regs(current));
694
695 switch (mode) {
696 case SECCOMP_MODE_STRICT:
697 __secure_computing_strict(this_syscall); /* may call do_exit */
698 return SECCOMP_PHASE1_OK;
699#ifdef CONFIG_SECCOMP_FILTER
700 case SECCOMP_MODE_FILTER:
701 return __seccomp_phase1_filter(this_syscall, sd);
702#endif
703 default:
704 BUG();
705 }
706}
707
708/**
709 * seccomp_phase2() - finish slow path seccomp work for the current syscall
710 * @phase1_result: The return value from seccomp_phase1()
711 *
712 * This must be called from a context in which ptrace hooks can be used.
713 *
714 * Returns 0 if the syscall should be processed or -1 to skip the syscall.
715 */
716int seccomp_phase2(u32 phase1_result)
717{
718 struct pt_regs *regs = task_pt_regs(current);
719 u32 action = phase1_result & SECCOMP_RET_ACTION;
720 int data = phase1_result & SECCOMP_RET_DATA;
721
722 BUG_ON(action != SECCOMP_RET_TRACE);
723
724 audit_seccomp(syscall_get_nr(current, regs), 0, action);
725
726 /* Skip these calls if there is no tracer. */
727 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
728 syscall_set_return_value(current, regs,
729 -ENOSYS, 0);
730 return -1;
731 }
732
733 /* Allow the BPF to provide the event message */
734 ptrace_event(PTRACE_EVENT_SECCOMP, data);
735 /*
736 * The delivery of a fatal signal during event
737 * notification may silently skip tracer notification.
738 * Terminating the task now avoids executing a system
739 * call that may not be intended.
740 */
741 if (fatal_signal_pending(current))
742 do_exit(SIGSYS);
743 if (syscall_get_nr(current, regs) < 0)
744 return -1; /* Explicit request to skip. */
745
746 return 0;
747}
748#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
749
750long prctl_get_seccomp(void)
751{
752 return current->seccomp.mode;
753}
754
755/**
756 * seccomp_set_mode_strict: internal function for setting strict seccomp
757 *
758 * Once current->seccomp.mode is non-zero, it may not be changed.
759 *
760 * Returns 0 on success or -EINVAL on failure.
761 */
762static long seccomp_set_mode_strict(void)
763{
764 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
765 long ret = -EINVAL;
766
767 spin_lock_irq(&current->sighand->siglock);
768
769 if (!seccomp_may_assign_mode(seccomp_mode))
770 goto out;
771
772#ifdef TIF_NOTSC
773 disable_TSC();
774#endif
775 seccomp_assign_mode(current, seccomp_mode);
776 ret = 0;
777
778out:
779 spin_unlock_irq(&current->sighand->siglock);
780
781 return ret;
782}
783
784#ifdef CONFIG_SECCOMP_FILTER
785/**
786 * seccomp_set_mode_filter: internal function for setting seccomp filter
787 * @flags: flags to change filter behavior
788 * @filter: struct sock_fprog containing filter
789 *
790 * This function may be called repeatedly to install additional filters.
791 * Every filter successfully installed will be evaluated (in reverse order)
792 * for each system call the task makes.
793 *
794 * Once current->seccomp.mode is non-zero, it may not be changed.
795 *
796 * Returns 0 on success or -EINVAL on failure.
797 */
798static long seccomp_set_mode_filter(unsigned int flags,
799 const char __user *filter)
800{
801 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
802 struct seccomp_filter *prepared = NULL;
803 long ret = -EINVAL;
804
805 /* Validate flags. */
806 if (flags & ~SECCOMP_FILTER_FLAG_MASK)
807 return -EINVAL;
808
809 /* Prepare the new filter before holding any locks. */
810 prepared = seccomp_prepare_user_filter(filter);
811 if (IS_ERR(prepared))
812 return PTR_ERR(prepared);
813
814 /*
815 * Make sure we cannot change seccomp or nnp state via TSYNC
816 * while another thread is in the middle of calling exec.
817 */
818 if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
819 mutex_lock_killable(&current->signal->cred_guard_mutex))
820 goto out_free;
821
822 spin_lock_irq(&current->sighand->siglock);
823
824 if (!seccomp_may_assign_mode(seccomp_mode))
825 goto out;
826
827 ret = seccomp_attach_filter(flags, prepared);
828 if (ret)
829 goto out;
830 /* Do not free the successfully attached filter. */
831 prepared = NULL;
832
833 seccomp_assign_mode(current, seccomp_mode);
834out:
835 spin_unlock_irq(&current->sighand->siglock);
836 if (flags & SECCOMP_FILTER_FLAG_TSYNC)
837 mutex_unlock(&current->signal->cred_guard_mutex);
838out_free:
839 seccomp_filter_free(prepared);
840 return ret;
841}
842#else
843static inline long seccomp_set_mode_filter(unsigned int flags,
844 const char __user *filter)
845{
846 return -EINVAL;
847}
848#endif
849
850/* Common entry point for both prctl and syscall. */
851static long do_seccomp(unsigned int op, unsigned int flags,
852 const char __user *uargs)
853{
854 switch (op) {
855 case SECCOMP_SET_MODE_STRICT:
856 if (flags != 0 || uargs != NULL)
857 return -EINVAL;
858 return seccomp_set_mode_strict();
859 case SECCOMP_SET_MODE_FILTER:
860 return seccomp_set_mode_filter(flags, uargs);
861 default:
862 return -EINVAL;
863 }
864}
865
866SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
867 const char __user *, uargs)
868{
869 return do_seccomp(op, flags, uargs);
870}
871
872/**
873 * prctl_set_seccomp: configures current->seccomp.mode
874 * @seccomp_mode: requested mode to use
875 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
876 *
877 * Returns 0 on success or -EINVAL on failure.
878 */
879long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
880{
881 unsigned int op;
882 char __user *uargs;
883
884 switch (seccomp_mode) {
885 case SECCOMP_MODE_STRICT:
886 op = SECCOMP_SET_MODE_STRICT;
887 /*
888 * Setting strict mode through prctl always ignored filter,
889 * so make sure it is always NULL here to pass the internal
890 * check in do_seccomp().
891 */
892 uargs = NULL;
893 break;
894 case SECCOMP_MODE_FILTER:
895 op = SECCOMP_SET_MODE_FILTER;
896 uargs = filter;
897 break;
898 default:
899 return -EINVAL;
900 }
901
902 /* prctl interface doesn't have flags, so they are always zero. */
903 return do_seccomp(op, 0, uargs);
904}