xref: /linux/kernel/seccomp.c (revision e4dcbdff114e2c0a8059c396e233aa5d9637afce)
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 #include <asm/syscall.h>
33 
34 /* Not exposed in headers: strictly internal use only. */
35 #define SECCOMP_MODE_DEAD	(SECCOMP_MODE_FILTER + 1)
36 
37 #ifdef CONFIG_SECCOMP_FILTER
38 #include <linux/file.h>
39 #include <linux/filter.h>
40 #include <linux/pid.h>
41 #include <linux/ptrace.h>
42 #include <linux/capability.h>
43 #include <linux/uaccess.h>
44 #include <linux/anon_inodes.h>
45 #include <linux/lockdep.h>
46 
47 /*
48  * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the
49  * wrong direction flag in the ioctl number. This is the broken one,
50  * which the kernel needs to keep supporting until all userspaces stop
51  * using the wrong command number.
52  */
53 #define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR	SECCOMP_IOR(2, __u64)
54 
55 enum notify_state {
56 	SECCOMP_NOTIFY_INIT,
57 	SECCOMP_NOTIFY_SENT,
58 	SECCOMP_NOTIFY_REPLIED,
59 };
60 
61 struct seccomp_knotif {
62 	/* The struct pid of the task whose filter triggered the notification */
63 	struct task_struct *task;
64 
65 	/* The "cookie" for this request; this is unique for this filter. */
66 	u64 id;
67 
68 	/*
69 	 * The seccomp data. This pointer is valid the entire time this
70 	 * notification is active, since it comes from __seccomp_filter which
71 	 * eclipses the entire lifecycle here.
72 	 */
73 	const struct seccomp_data *data;
74 
75 	/*
76 	 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
77 	 * struct seccomp_knotif is created and starts out in INIT. Once the
78 	 * handler reads the notification off of an FD, it transitions to SENT.
79 	 * If a signal is received the state transitions back to INIT and
80 	 * another message is sent. When the userspace handler replies, state
81 	 * transitions to REPLIED.
82 	 */
83 	enum notify_state state;
84 
85 	/* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
86 	int error;
87 	long val;
88 	u32 flags;
89 
90 	/*
91 	 * Signals when this has changed states, such as the listener
92 	 * dying, a new seccomp addfd message, or changing to REPLIED
93 	 */
94 	struct completion ready;
95 
96 	struct list_head list;
97 
98 	/* outstanding addfd requests */
99 	struct list_head addfd;
100 };
101 
102 /**
103  * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages
104  *
105  * @file: A reference to the file to install in the other task
106  * @fd: The fd number to install it at. If the fd number is -1, it means the
107  *      installing process should allocate the fd as normal.
108  * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC
109  *         is allowed.
110  * @ioctl_flags: The flags used for the seccomp_addfd ioctl.
111  * @setfd: whether or not SECCOMP_ADDFD_FLAG_SETFD was set during notify_addfd
112  * @ret: The return value of the installing process. It is set to the fd num
113  *       upon success (>= 0).
114  * @completion: Indicates that the installing process has completed fd
115  *              installation, or gone away (either due to successful
116  *              reply, or signal)
117  * @list: list_head for chaining seccomp_kaddfd together.
118  *
119  */
120 struct seccomp_kaddfd {
121 	struct file *file;
122 	int fd;
123 	unsigned int flags;
124 	__u32 ioctl_flags;
125 
126 	union {
127 		bool setfd;
128 		/* To only be set on reply */
129 		int ret;
130 	};
131 	struct completion completion;
132 	struct list_head list;
133 };
134 
135 /**
136  * struct notification - container for seccomp userspace notifications. Since
137  * most seccomp filters will not have notification listeners attached and this
138  * structure is fairly large, we store the notification-specific stuff in a
139  * separate structure.
140  *
141  * @requests: A semaphore that users of this notification can wait on for
142  *            changes. Actual reads and writes are still controlled with
143  *            filter->notify_lock.
144  * @flags: A set of SECCOMP_USER_NOTIF_FD_* flags.
145  * @next_id: The id of the next request.
146  * @notifications: A list of struct seccomp_knotif elements.
147  */
148 
149 struct notification {
150 	atomic_t requests;
151 	u32 flags;
152 	u64 next_id;
153 	struct list_head notifications;
154 };
155 
156 #ifdef SECCOMP_ARCH_NATIVE
157 /**
158  * struct action_cache - per-filter cache of seccomp actions per
159  * arch/syscall pair
160  *
161  * @allow_native: A bitmap where each bit represents whether the
162  *		  filter will always allow the syscall, for the
163  *		  native architecture.
164  * @allow_compat: A bitmap where each bit represents whether the
165  *		  filter will always allow the syscall, for the
166  *		  compat architecture.
167  */
168 struct action_cache {
169 	DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR);
170 #ifdef SECCOMP_ARCH_COMPAT
171 	DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR);
172 #endif
173 };
174 #else
175 struct action_cache { };
176 
seccomp_cache_check_allow(const struct seccomp_filter * sfilter,const struct seccomp_data * sd)177 static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
178 					     const struct seccomp_data *sd)
179 {
180 	return false;
181 }
182 
seccomp_cache_prepare(struct seccomp_filter * sfilter)183 static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
184 {
185 }
186 #endif /* SECCOMP_ARCH_NATIVE */
187 
188 /**
189  * struct seccomp_filter - container for seccomp BPF programs
190  *
191  * @refs: Reference count to manage the object lifetime.
192  *	  A filter's reference count is incremented for each directly
193  *	  attached task, once for the dependent filter, and if
194  *	  requested for the user notifier. When @refs reaches zero,
195  *	  the filter can be freed.
196  * @users: A filter's @users count is incremented for each directly
197  *         attached task (filter installation, fork(), thread_sync),
198  *	   and once for the dependent filter (tracked in filter->prev).
199  *	   When it reaches zero it indicates that no direct or indirect
200  *	   users of that filter exist. No new tasks can get associated with
201  *	   this filter after reaching 0. The @users count is always smaller
202  *	   or equal to @refs. Hence, reaching 0 for @users does not mean
203  *	   the filter can be freed.
204  * @cache: cache of arch/syscall mappings to actions
205  * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
206  * @wait_killable_recv: Put notifying process in killable state once the
207  *			notification is received by the userspace listener.
208  * @prev: points to a previously installed, or inherited, filter
209  * @prog: the BPF program to evaluate
210  * @notif: the struct that holds all notification related information
211  * @notify_lock: A lock for all notification-related accesses.
212  * @wqh: A wait queue for poll if a notifier is in use.
213  *
214  * seccomp_filter objects are organized in a tree linked via the @prev
215  * pointer.  For any task, it appears to be a singly-linked list starting
216  * with current->seccomp.filter, the most recently attached or inherited filter.
217  * However, multiple filters may share a @prev node, by way of fork(), which
218  * results in a unidirectional tree existing in memory.  This is similar to
219  * how namespaces work.
220  *
221  * seccomp_filter objects should never be modified after being attached
222  * to a task_struct (other than @refs).
223  */
224 struct seccomp_filter {
225 	refcount_t refs;
226 	refcount_t users;
227 	bool log;
228 	bool wait_killable_recv;
229 	struct action_cache cache;
230 	struct seccomp_filter *prev;
231 	struct bpf_prog *prog;
232 	struct notification *notif;
233 	struct mutex notify_lock;
234 	wait_queue_head_t wqh;
235 };
236 
237 /* Limit any path through the tree to 256KB worth of instructions. */
238 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
239 
240 /*
241  * Endianness is explicitly ignored and left for BPF program authors to manage
242  * as per the specific architecture.
243  */
populate_seccomp_data(struct seccomp_data * sd)244 static void populate_seccomp_data(struct seccomp_data *sd)
245 {
246 	/*
247 	 * Instead of using current_pt_reg(), we're already doing the work
248 	 * to safely fetch "current", so just use "task" everywhere below.
249 	 */
250 	struct task_struct *task = current;
251 	struct pt_regs *regs = task_pt_regs(task);
252 	unsigned long args[6];
253 
254 	sd->nr = syscall_get_nr(task, regs);
255 	sd->arch = syscall_get_arch(task);
256 	syscall_get_arguments(task, regs, args);
257 	sd->args[0] = args[0];
258 	sd->args[1] = args[1];
259 	sd->args[2] = args[2];
260 	sd->args[3] = args[3];
261 	sd->args[4] = args[4];
262 	sd->args[5] = args[5];
263 	sd->instruction_pointer = KSTK_EIP(task);
264 }
265 
266 /**
267  *	seccomp_check_filter - verify seccomp filter code
268  *	@filter: filter to verify
269  *	@flen: length of filter
270  *
271  * Takes a previously checked filter (by bpf_check_classic) and
272  * redirects all filter code that loads struct sk_buff data
273  * and related data through seccomp_bpf_load.  It also
274  * enforces length and alignment checking of those loads.
275  *
276  * Returns 0 if the rule set is legal or -EINVAL if not.
277  */
seccomp_check_filter(struct sock_filter * filter,unsigned int flen)278 static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
279 {
280 	int pc;
281 	for (pc = 0; pc < flen; pc++) {
282 		struct sock_filter *ftest = &filter[pc];
283 		u16 code = ftest->code;
284 		u32 k = ftest->k;
285 
286 		switch (code) {
287 		case BPF_LD | BPF_W | BPF_ABS:
288 			ftest->code = BPF_LDX | BPF_W | BPF_ABS;
289 			/* 32-bit aligned and not out of bounds. */
290 			if (k >= sizeof(struct seccomp_data) || k & 3)
291 				return -EINVAL;
292 			continue;
293 		case BPF_LD | BPF_W | BPF_LEN:
294 			ftest->code = BPF_LD | BPF_IMM;
295 			ftest->k = sizeof(struct seccomp_data);
296 			continue;
297 		case BPF_LDX | BPF_W | BPF_LEN:
298 			ftest->code = BPF_LDX | BPF_IMM;
299 			ftest->k = sizeof(struct seccomp_data);
300 			continue;
301 		/* Explicitly include allowed calls. */
302 		case BPF_RET | BPF_K:
303 		case BPF_RET | BPF_A:
304 		case BPF_ALU | BPF_ADD | BPF_K:
305 		case BPF_ALU | BPF_ADD | BPF_X:
306 		case BPF_ALU | BPF_SUB | BPF_K:
307 		case BPF_ALU | BPF_SUB | BPF_X:
308 		case BPF_ALU | BPF_MUL | BPF_K:
309 		case BPF_ALU | BPF_MUL | BPF_X:
310 		case BPF_ALU | BPF_DIV | BPF_K:
311 		case BPF_ALU | BPF_DIV | BPF_X:
312 		case BPF_ALU | BPF_AND | BPF_K:
313 		case BPF_ALU | BPF_AND | BPF_X:
314 		case BPF_ALU | BPF_OR | BPF_K:
315 		case BPF_ALU | BPF_OR | BPF_X:
316 		case BPF_ALU | BPF_XOR | BPF_K:
317 		case BPF_ALU | BPF_XOR | BPF_X:
318 		case BPF_ALU | BPF_LSH | BPF_K:
319 		case BPF_ALU | BPF_LSH | BPF_X:
320 		case BPF_ALU | BPF_RSH | BPF_K:
321 		case BPF_ALU | BPF_RSH | BPF_X:
322 		case BPF_ALU | BPF_NEG:
323 		case BPF_LD | BPF_IMM:
324 		case BPF_LDX | BPF_IMM:
325 		case BPF_MISC | BPF_TAX:
326 		case BPF_MISC | BPF_TXA:
327 		case BPF_LD | BPF_MEM:
328 		case BPF_LDX | BPF_MEM:
329 		case BPF_ST:
330 		case BPF_STX:
331 		case BPF_JMP | BPF_JA:
332 		case BPF_JMP | BPF_JEQ | BPF_K:
333 		case BPF_JMP | BPF_JEQ | BPF_X:
334 		case BPF_JMP | BPF_JGE | BPF_K:
335 		case BPF_JMP | BPF_JGE | BPF_X:
336 		case BPF_JMP | BPF_JGT | BPF_K:
337 		case BPF_JMP | BPF_JGT | BPF_X:
338 		case BPF_JMP | BPF_JSET | BPF_K:
339 		case BPF_JMP | BPF_JSET | BPF_X:
340 			continue;
341 		default:
342 			return -EINVAL;
343 		}
344 	}
345 	return 0;
346 }
347 
348 #ifdef SECCOMP_ARCH_NATIVE
seccomp_cache_check_allow_bitmap(const void * bitmap,size_t bitmap_size,int syscall_nr)349 static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap,
350 						    size_t bitmap_size,
351 						    int syscall_nr)
352 {
353 	if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size))
354 		return false;
355 	syscall_nr = array_index_nospec(syscall_nr, bitmap_size);
356 
357 	return test_bit(syscall_nr, bitmap);
358 }
359 
360 /**
361  * seccomp_cache_check_allow - lookup seccomp cache
362  * @sfilter: The seccomp filter
363  * @sd: The seccomp data to lookup the cache with
364  *
365  * Returns true if the seccomp_data is cached and allowed.
366  */
seccomp_cache_check_allow(const struct seccomp_filter * sfilter,const struct seccomp_data * sd)367 static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
368 					     const struct seccomp_data *sd)
369 {
370 	int syscall_nr = sd->nr;
371 	const struct action_cache *cache = &sfilter->cache;
372 
373 #ifndef SECCOMP_ARCH_COMPAT
374 	/* A native-only architecture doesn't need to check sd->arch. */
375 	return seccomp_cache_check_allow_bitmap(cache->allow_native,
376 						SECCOMP_ARCH_NATIVE_NR,
377 						syscall_nr);
378 #else
379 	if (likely(sd->arch == SECCOMP_ARCH_NATIVE))
380 		return seccomp_cache_check_allow_bitmap(cache->allow_native,
381 							SECCOMP_ARCH_NATIVE_NR,
382 							syscall_nr);
383 	if (likely(sd->arch == SECCOMP_ARCH_COMPAT))
384 		return seccomp_cache_check_allow_bitmap(cache->allow_compat,
385 							SECCOMP_ARCH_COMPAT_NR,
386 							syscall_nr);
387 #endif /* SECCOMP_ARCH_COMPAT */
388 
389 	WARN_ON_ONCE(true);
390 	return false;
391 }
392 #endif /* SECCOMP_ARCH_NATIVE */
393 
394 #define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
395 /**
396  * seccomp_run_filters - evaluates all seccomp filters against @sd
397  * @sd: optional seccomp data to be passed to filters
398  * @match: stores struct seccomp_filter that resulted in the return value,
399  *         unless filter returned SECCOMP_RET_ALLOW, in which case it will
400  *         be unchanged.
401  *
402  * Returns valid seccomp BPF response codes.
403  */
seccomp_run_filters(const struct seccomp_data * sd,struct seccomp_filter ** match)404 static u32 seccomp_run_filters(const struct seccomp_data *sd,
405 			       struct seccomp_filter **match)
406 {
407 	u32 ret = SECCOMP_RET_ALLOW;
408 	/* Make sure cross-thread synced filter points somewhere sane. */
409 	struct seccomp_filter *f =
410 			READ_ONCE(current->seccomp.filter);
411 
412 	/* Ensure unexpected behavior doesn't result in failing open. */
413 	if (WARN_ON(f == NULL))
414 		return SECCOMP_RET_KILL_PROCESS;
415 
416 	if (seccomp_cache_check_allow(f, sd))
417 		return SECCOMP_RET_ALLOW;
418 
419 	/*
420 	 * All filters in the list are evaluated and the lowest BPF return
421 	 * value always takes priority (ignoring the DATA).
422 	 */
423 	for (; f; f = f->prev) {
424 		u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd);
425 
426 		if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
427 			ret = cur_ret;
428 			*match = f;
429 		}
430 	}
431 	return ret;
432 }
433 #endif /* CONFIG_SECCOMP_FILTER */
434 
seccomp_may_assign_mode(unsigned long seccomp_mode)435 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
436 {
437 	assert_spin_locked(&current->sighand->siglock);
438 
439 	if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
440 		return false;
441 
442 	return true;
443 }
444 
arch_seccomp_spec_mitigate(struct task_struct * task)445 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
446 
seccomp_assign_mode(struct task_struct * task,unsigned long seccomp_mode,unsigned long flags)447 static inline void seccomp_assign_mode(struct task_struct *task,
448 				       unsigned long seccomp_mode,
449 				       unsigned long flags)
450 {
451 	assert_spin_locked(&task->sighand->siglock);
452 
453 	task->seccomp.mode = seccomp_mode;
454 	/*
455 	 * Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and
456 	 * filter) is set.
457 	 */
458 	smp_mb__before_atomic();
459 	/* Assume default seccomp processes want spec flaw mitigation. */
460 	if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
461 		arch_seccomp_spec_mitigate(task);
462 	set_task_syscall_work(task, SECCOMP);
463 }
464 
465 #ifdef CONFIG_SECCOMP_FILTER
466 /* Returns 1 if the parent is an ancestor of the child. */
is_ancestor(struct seccomp_filter * parent,struct seccomp_filter * child)467 static int is_ancestor(struct seccomp_filter *parent,
468 		       struct seccomp_filter *child)
469 {
470 	/* NULL is the root ancestor. */
471 	if (parent == NULL)
472 		return 1;
473 	for (; child; child = child->prev)
474 		if (child == parent)
475 			return 1;
476 	return 0;
477 }
478 
479 /**
480  * seccomp_can_sync_threads: checks if all threads can be synchronized
481  *
482  * Expects sighand and cred_guard_mutex locks to be held.
483  *
484  * Returns 0 on success, -ve on error, or the pid of a thread which was
485  * either not in the correct seccomp mode or did not have an ancestral
486  * seccomp filter.
487  */
seccomp_can_sync_threads(void)488 static inline pid_t seccomp_can_sync_threads(void)
489 {
490 	struct task_struct *thread, *caller;
491 
492 	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
493 	assert_spin_locked(&current->sighand->siglock);
494 
495 	/* Validate all threads being eligible for synchronization. */
496 	caller = current;
497 	for_each_thread(caller, thread) {
498 		pid_t failed;
499 
500 		/* Skip current, since it is initiating the sync. */
501 		if (thread == caller)
502 			continue;
503 		/* Skip exited threads. */
504 		if (thread->flags & PF_EXITING)
505 			continue;
506 
507 		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
508 		    (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
509 		     is_ancestor(thread->seccomp.filter,
510 				 caller->seccomp.filter)))
511 			continue;
512 
513 		/* Return the first thread that cannot be synchronized. */
514 		failed = task_pid_vnr(thread);
515 		/* If the pid cannot be resolved, then return -ESRCH */
516 		if (WARN_ON(failed == 0))
517 			failed = -ESRCH;
518 		return failed;
519 	}
520 
521 	return 0;
522 }
523 
seccomp_filter_free(struct seccomp_filter * filter)524 static inline void seccomp_filter_free(struct seccomp_filter *filter)
525 {
526 	if (filter) {
527 		bpf_prog_destroy(filter->prog);
528 		kfree(filter);
529 	}
530 }
531 
__seccomp_filter_orphan(struct seccomp_filter * orig)532 static void __seccomp_filter_orphan(struct seccomp_filter *orig)
533 {
534 	while (orig && refcount_dec_and_test(&orig->users)) {
535 		if (waitqueue_active(&orig->wqh))
536 			wake_up_poll(&orig->wqh, EPOLLHUP);
537 		orig = orig->prev;
538 	}
539 }
540 
__put_seccomp_filter(struct seccomp_filter * orig)541 static void __put_seccomp_filter(struct seccomp_filter *orig)
542 {
543 	/* Clean up single-reference branches iteratively. */
544 	while (orig && refcount_dec_and_test(&orig->refs)) {
545 		struct seccomp_filter *freeme = orig;
546 		orig = orig->prev;
547 		seccomp_filter_free(freeme);
548 	}
549 }
550 
__seccomp_filter_release(struct seccomp_filter * orig)551 static void __seccomp_filter_release(struct seccomp_filter *orig)
552 {
553 	/* Notify about any unused filters in the task's former filter tree. */
554 	__seccomp_filter_orphan(orig);
555 	/* Finally drop all references to the task's former tree. */
556 	__put_seccomp_filter(orig);
557 }
558 
559 /**
560  * seccomp_filter_release - Detach the task from its filter tree,
561  *			    drop its reference count, and notify
562  *			    about unused filters
563  *
564  * @tsk: task the filter should be released from.
565  *
566  * This function should only be called when the task is exiting as
567  * it detaches it from its filter tree. PF_EXITING has to be set
568  * for the task.
569  */
seccomp_filter_release(struct task_struct * tsk)570 void seccomp_filter_release(struct task_struct *tsk)
571 {
572 	struct seccomp_filter *orig;
573 
574 	if (WARN_ON((tsk->flags & PF_EXITING) == 0))
575 		return;
576 
577 	if (READ_ONCE(tsk->seccomp.filter) == NULL)
578 		return;
579 
580 	spin_lock_irq(&tsk->sighand->siglock);
581 	orig = tsk->seccomp.filter;
582 	/* Detach task from its filter tree. */
583 	tsk->seccomp.filter = NULL;
584 	spin_unlock_irq(&tsk->sighand->siglock);
585 	__seccomp_filter_release(orig);
586 }
587 
588 /**
589  * seccomp_sync_threads: sets all threads to use current's filter
590  *
591  * @flags: SECCOMP_FILTER_FLAG_* flags to set during sync.
592  *
593  * Expects sighand and cred_guard_mutex locks to be held, and for
594  * seccomp_can_sync_threads() to have returned success already
595  * without dropping the locks.
596  *
597  */
seccomp_sync_threads(unsigned long flags)598 static inline void seccomp_sync_threads(unsigned long flags)
599 {
600 	struct task_struct *thread, *caller;
601 
602 	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
603 	assert_spin_locked(&current->sighand->siglock);
604 
605 	/*
606 	 * Don't touch any of the threads if the process is being killed.
607 	 * This allows for a lockless check in seccomp_filter_release.
608 	 */
609 	if (current->signal->flags & SIGNAL_GROUP_EXIT)
610 		return;
611 
612 	/* Synchronize all threads. */
613 	caller = current;
614 	for_each_thread(caller, thread) {
615 		/* Skip current, since it needs no changes. */
616 		if (thread == caller)
617 			continue;
618 
619 		/*
620 		 * Skip exited threads. seccomp_filter_release could have
621 		 * been already called for this task.
622 		 */
623 		if (thread->flags & PF_EXITING)
624 			continue;
625 
626 		/* Get a task reference for the new leaf node. */
627 		get_seccomp_filter(caller);
628 
629 		/*
630 		 * Drop the task reference to the shared ancestor since
631 		 * current's path will hold a reference.  (This also
632 		 * allows a put before the assignment.)
633 		 */
634 		__seccomp_filter_release(thread->seccomp.filter);
635 
636 		/* Make our new filter tree visible. */
637 		smp_store_release(&thread->seccomp.filter,
638 				  caller->seccomp.filter);
639 		atomic_set(&thread->seccomp.filter_count,
640 			   atomic_read(&caller->seccomp.filter_count));
641 
642 		/*
643 		 * Don't let an unprivileged task work around
644 		 * the no_new_privs restriction by creating
645 		 * a thread that sets it up, enters seccomp,
646 		 * then dies.
647 		 */
648 		if (task_no_new_privs(caller))
649 			task_set_no_new_privs(thread);
650 
651 		/*
652 		 * Opt the other thread into seccomp if needed.
653 		 * As threads are considered to be trust-realm
654 		 * equivalent (see ptrace_may_access), it is safe to
655 		 * allow one thread to transition the other.
656 		 */
657 		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
658 			seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
659 					    flags);
660 	}
661 }
662 
663 /**
664  * seccomp_prepare_filter: Prepares a seccomp filter for use.
665  * @fprog: BPF program to install
666  *
667  * Returns filter on success or an ERR_PTR on failure.
668  */
seccomp_prepare_filter(struct sock_fprog * fprog)669 static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
670 {
671 	struct seccomp_filter *sfilter;
672 	int ret;
673 	const bool save_orig =
674 #if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE)
675 		true;
676 #else
677 		false;
678 #endif
679 
680 	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
681 		return ERR_PTR(-EINVAL);
682 
683 	BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
684 
685 	/*
686 	 * Installing a seccomp filter requires that the task has
687 	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
688 	 * This avoids scenarios where unprivileged tasks can affect the
689 	 * behavior of privileged children.
690 	 */
691 	if (!task_no_new_privs(current) &&
692 			!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
693 		return ERR_PTR(-EACCES);
694 
695 	/* Allocate a new seccomp_filter */
696 	sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
697 	if (!sfilter)
698 		return ERR_PTR(-ENOMEM);
699 
700 	mutex_init(&sfilter->notify_lock);
701 	ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
702 					seccomp_check_filter, save_orig);
703 	if (ret < 0) {
704 		kfree(sfilter);
705 		return ERR_PTR(ret);
706 	}
707 
708 	refcount_set(&sfilter->refs, 1);
709 	refcount_set(&sfilter->users, 1);
710 	init_waitqueue_head(&sfilter->wqh);
711 
712 	return sfilter;
713 }
714 
715 /**
716  * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
717  * @user_filter: pointer to the user data containing a sock_fprog.
718  *
719  * Returns 0 on success and non-zero otherwise.
720  */
721 static struct seccomp_filter *
seccomp_prepare_user_filter(const char __user * user_filter)722 seccomp_prepare_user_filter(const char __user *user_filter)
723 {
724 	struct sock_fprog fprog;
725 	struct seccomp_filter *filter = ERR_PTR(-EFAULT);
726 
727 #ifdef CONFIG_COMPAT
728 	if (in_compat_syscall()) {
729 		struct compat_sock_fprog fprog32;
730 		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
731 			goto out;
732 		fprog.len = fprog32.len;
733 		fprog.filter = compat_ptr(fprog32.filter);
734 	} else /* falls through to the if below. */
735 #endif
736 	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
737 		goto out;
738 	filter = seccomp_prepare_filter(&fprog);
739 out:
740 	return filter;
741 }
742 
743 #ifdef SECCOMP_ARCH_NATIVE
seccomp_uprobe_exception(struct seccomp_data * sd)744 static bool seccomp_uprobe_exception(struct seccomp_data *sd)
745 {
746 #if defined __NR_uretprobe || defined __NR_uprobe
747 #ifdef SECCOMP_ARCH_COMPAT
748 	if (sd->arch == SECCOMP_ARCH_NATIVE)
749 #endif
750 	{
751 #ifdef __NR_uretprobe
752 		if (sd->nr == __NR_uretprobe)
753 			return true;
754 #endif
755 #ifdef __NR_uprobe
756 		if (sd->nr == __NR_uprobe)
757 			return true;
758 #endif
759 	}
760 #endif
761 	return false;
762 }
763 
764 /**
765  * seccomp_is_const_allow - check if filter is constant allow with given data
766  * @fprog: The BPF programs
767  * @sd: The seccomp data to check against, only syscall number and arch
768  *      number are considered constant.
769  */
seccomp_is_const_allow(struct sock_fprog_kern * fprog,struct seccomp_data * sd)770 static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog,
771 				   struct seccomp_data *sd)
772 {
773 	unsigned int reg_value = 0;
774 	unsigned int pc;
775 	bool op_res;
776 
777 	if (WARN_ON_ONCE(!fprog))
778 		return false;
779 
780 	/* Our single exception to filtering. */
781 	if (seccomp_uprobe_exception(sd))
782 		return true;
783 
784 	for (pc = 0; pc < fprog->len; pc++) {
785 		struct sock_filter *insn = &fprog->filter[pc];
786 		u16 code = insn->code;
787 		u32 k = insn->k;
788 
789 		switch (code) {
790 		case BPF_LD | BPF_W | BPF_ABS:
791 			switch (k) {
792 			case offsetof(struct seccomp_data, nr):
793 				reg_value = sd->nr;
794 				break;
795 			case offsetof(struct seccomp_data, arch):
796 				reg_value = sd->arch;
797 				break;
798 			default:
799 				/* can't optimize (non-constant value load) */
800 				return false;
801 			}
802 			break;
803 		case BPF_RET | BPF_K:
804 			/* reached return with constant values only, check allow */
805 			return k == SECCOMP_RET_ALLOW;
806 		case BPF_JMP | BPF_JA:
807 			pc += insn->k;
808 			break;
809 		case BPF_JMP | BPF_JEQ | BPF_K:
810 		case BPF_JMP | BPF_JGE | BPF_K:
811 		case BPF_JMP | BPF_JGT | BPF_K:
812 		case BPF_JMP | BPF_JSET | BPF_K:
813 			switch (BPF_OP(code)) {
814 			case BPF_JEQ:
815 				op_res = reg_value == k;
816 				break;
817 			case BPF_JGE:
818 				op_res = reg_value >= k;
819 				break;
820 			case BPF_JGT:
821 				op_res = reg_value > k;
822 				break;
823 			case BPF_JSET:
824 				op_res = !!(reg_value & k);
825 				break;
826 			default:
827 				/* can't optimize (unknown jump) */
828 				return false;
829 			}
830 
831 			pc += op_res ? insn->jt : insn->jf;
832 			break;
833 		case BPF_ALU | BPF_AND | BPF_K:
834 			reg_value &= k;
835 			break;
836 		default:
837 			/* can't optimize (unknown insn) */
838 			return false;
839 		}
840 	}
841 
842 	/* ran off the end of the filter?! */
843 	WARN_ON(1);
844 	return false;
845 }
846 
seccomp_cache_prepare_bitmap(struct seccomp_filter * sfilter,void * bitmap,const void * bitmap_prev,size_t bitmap_size,int arch)847 static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter,
848 					 void *bitmap, const void *bitmap_prev,
849 					 size_t bitmap_size, int arch)
850 {
851 	struct sock_fprog_kern *fprog = sfilter->prog->orig_prog;
852 	struct seccomp_data sd;
853 	int nr;
854 
855 	if (bitmap_prev) {
856 		/* The new filter must be as restrictive as the last. */
857 		bitmap_copy(bitmap, bitmap_prev, bitmap_size);
858 	} else {
859 		/* Before any filters, all syscalls are always allowed. */
860 		bitmap_fill(bitmap, bitmap_size);
861 	}
862 
863 	for (nr = 0; nr < bitmap_size; nr++) {
864 		/* No bitmap change: not a cacheable action. */
865 		if (!test_bit(nr, bitmap))
866 			continue;
867 
868 		sd.nr = nr;
869 		sd.arch = arch;
870 
871 		/* No bitmap change: continue to always allow. */
872 		if (seccomp_is_const_allow(fprog, &sd))
873 			continue;
874 
875 		/*
876 		 * Not a cacheable action: always run filters.
877 		 * atomic clear_bit() not needed, filter not visible yet.
878 		 */
879 		__clear_bit(nr, bitmap);
880 	}
881 }
882 
883 /**
884  * seccomp_cache_prepare - emulate the filter to find cacheable syscalls
885  * @sfilter: The seccomp filter
886  *
887  * Returns 0 if successful or -errno if error occurred.
888  */
seccomp_cache_prepare(struct seccomp_filter * sfilter)889 static void seccomp_cache_prepare(struct seccomp_filter *sfilter)
890 {
891 	struct action_cache *cache = &sfilter->cache;
892 	const struct action_cache *cache_prev =
893 		sfilter->prev ? &sfilter->prev->cache : NULL;
894 
895 	seccomp_cache_prepare_bitmap(sfilter, cache->allow_native,
896 				     cache_prev ? cache_prev->allow_native : NULL,
897 				     SECCOMP_ARCH_NATIVE_NR,
898 				     SECCOMP_ARCH_NATIVE);
899 
900 #ifdef SECCOMP_ARCH_COMPAT
901 	seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat,
902 				     cache_prev ? cache_prev->allow_compat : NULL,
903 				     SECCOMP_ARCH_COMPAT_NR,
904 				     SECCOMP_ARCH_COMPAT);
905 #endif /* SECCOMP_ARCH_COMPAT */
906 }
907 #endif /* SECCOMP_ARCH_NATIVE */
908 
909 /**
910  * seccomp_attach_filter: validate and attach filter
911  * @flags:  flags to change filter behavior
912  * @filter: seccomp filter to add to the current process
913  *
914  * Caller must be holding current->sighand->siglock lock.
915  *
916  * Returns 0 on success, -ve on error, or
917  *   - in TSYNC mode: the pid of a thread which was either not in the correct
918  *     seccomp mode or did not have an ancestral seccomp filter
919  *   - in NEW_LISTENER mode: the fd of the new listener
920  */
seccomp_attach_filter(unsigned int flags,struct seccomp_filter * filter)921 static long seccomp_attach_filter(unsigned int flags,
922 				  struct seccomp_filter *filter)
923 {
924 	unsigned long total_insns;
925 	struct seccomp_filter *walker;
926 
927 	assert_spin_locked(&current->sighand->siglock);
928 
929 	/* Validate resulting filter length. */
930 	total_insns = filter->prog->len;
931 	for (walker = current->seccomp.filter; walker; walker = walker->prev)
932 		total_insns += walker->prog->len + 4;  /* 4 instr penalty */
933 	if (total_insns > MAX_INSNS_PER_PATH)
934 		return -ENOMEM;
935 
936 	/* If thread sync has been requested, check that it is possible. */
937 	if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
938 		int ret;
939 
940 		ret = seccomp_can_sync_threads();
941 		if (ret) {
942 			if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH)
943 				return -ESRCH;
944 			else
945 				return ret;
946 		}
947 	}
948 
949 	/* Set log flag, if present. */
950 	if (flags & SECCOMP_FILTER_FLAG_LOG)
951 		filter->log = true;
952 
953 	/* Set wait killable flag, if present. */
954 	if (flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV)
955 		filter->wait_killable_recv = true;
956 
957 	/*
958 	 * If there is an existing filter, make it the prev and don't drop its
959 	 * task reference.
960 	 */
961 	filter->prev = current->seccomp.filter;
962 	seccomp_cache_prepare(filter);
963 	current->seccomp.filter = filter;
964 	atomic_inc(&current->seccomp.filter_count);
965 
966 	/* Now that the new filter is in place, synchronize to all threads. */
967 	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
968 		seccomp_sync_threads(flags);
969 
970 	return 0;
971 }
972 
__get_seccomp_filter(struct seccomp_filter * filter)973 static void __get_seccomp_filter(struct seccomp_filter *filter)
974 {
975 	refcount_inc(&filter->refs);
976 }
977 
978 /* get_seccomp_filter - increments the reference count of the filter on @tsk */
get_seccomp_filter(struct task_struct * tsk)979 void get_seccomp_filter(struct task_struct *tsk)
980 {
981 	struct seccomp_filter *orig = tsk->seccomp.filter;
982 	if (!orig)
983 		return;
984 	__get_seccomp_filter(orig);
985 	refcount_inc(&orig->users);
986 }
987 
988 #endif	/* CONFIG_SECCOMP_FILTER */
989 
990 /* For use with seccomp_actions_logged */
991 #define SECCOMP_LOG_KILL_PROCESS	(1 << 0)
992 #define SECCOMP_LOG_KILL_THREAD		(1 << 1)
993 #define SECCOMP_LOG_TRAP		(1 << 2)
994 #define SECCOMP_LOG_ERRNO		(1 << 3)
995 #define SECCOMP_LOG_TRACE		(1 << 4)
996 #define SECCOMP_LOG_LOG			(1 << 5)
997 #define SECCOMP_LOG_ALLOW		(1 << 6)
998 #define SECCOMP_LOG_USER_NOTIF		(1 << 7)
999 
1000 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
1001 				    SECCOMP_LOG_KILL_THREAD  |
1002 				    SECCOMP_LOG_TRAP  |
1003 				    SECCOMP_LOG_ERRNO |
1004 				    SECCOMP_LOG_USER_NOTIF |
1005 				    SECCOMP_LOG_TRACE |
1006 				    SECCOMP_LOG_LOG;
1007 
seccomp_log(unsigned long syscall,long signr,u32 action,bool requested)1008 static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
1009 			       bool requested)
1010 {
1011 	bool log = false;
1012 
1013 	switch (action) {
1014 	case SECCOMP_RET_ALLOW:
1015 		break;
1016 	case SECCOMP_RET_TRAP:
1017 		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
1018 		break;
1019 	case SECCOMP_RET_ERRNO:
1020 		log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
1021 		break;
1022 	case SECCOMP_RET_TRACE:
1023 		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
1024 		break;
1025 	case SECCOMP_RET_USER_NOTIF:
1026 		log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
1027 		break;
1028 	case SECCOMP_RET_LOG:
1029 		log = seccomp_actions_logged & SECCOMP_LOG_LOG;
1030 		break;
1031 	case SECCOMP_RET_KILL_THREAD:
1032 		log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
1033 		break;
1034 	case SECCOMP_RET_KILL_PROCESS:
1035 	default:
1036 		log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
1037 	}
1038 
1039 	/*
1040 	 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
1041 	 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
1042 	 * any action from being logged by removing the action name from the
1043 	 * seccomp_actions_logged sysctl.
1044 	 */
1045 	if (!log)
1046 		return;
1047 
1048 	audit_seccomp(syscall, signr, action);
1049 }
1050 
1051 /*
1052  * Secure computing mode 1 allows only read/write/exit/sigreturn.
1053  * To be fully secure this must be combined with rlimit
1054  * to limit the stack allocations too.
1055  */
1056 static const int mode1_syscalls[] = {
1057 	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
1058 #ifdef __NR_uretprobe
1059 	__NR_uretprobe,
1060 #endif
1061 #ifdef __NR_uprobe
1062 	__NR_uprobe,
1063 #endif
1064 	-1, /* negative terminated */
1065 };
1066 
__secure_computing_strict(int this_syscall)1067 static void __secure_computing_strict(int this_syscall)
1068 {
1069 	const int *allowed_syscalls = mode1_syscalls;
1070 #ifdef CONFIG_COMPAT
1071 	if (in_compat_syscall())
1072 		allowed_syscalls = get_compat_mode1_syscalls();
1073 #endif
1074 	do {
1075 		if (*allowed_syscalls == this_syscall)
1076 			return;
1077 	} while (*++allowed_syscalls != -1);
1078 
1079 #ifdef SECCOMP_DEBUG
1080 	dump_stack();
1081 #endif
1082 	current->seccomp.mode = SECCOMP_MODE_DEAD;
1083 	seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
1084 	do_exit(SIGKILL);
1085 }
1086 
1087 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
secure_computing_strict(int this_syscall)1088 void secure_computing_strict(int this_syscall)
1089 {
1090 	int mode = current->seccomp.mode;
1091 
1092 	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1093 	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1094 		return;
1095 
1096 	if (mode == SECCOMP_MODE_DISABLED)
1097 		return;
1098 	else if (mode == SECCOMP_MODE_STRICT)
1099 		__secure_computing_strict(this_syscall);
1100 	else
1101 		BUG();
1102 }
__secure_computing(void)1103 int __secure_computing(void)
1104 {
1105 	int this_syscall = syscall_get_nr(current, current_pt_regs());
1106 
1107 	secure_computing_strict(this_syscall);
1108 	return 0;
1109 }
1110 #else
1111 
1112 #ifdef CONFIG_SECCOMP_FILTER
seccomp_next_notify_id(struct seccomp_filter * filter)1113 static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
1114 {
1115 	/*
1116 	 * Note: overflow is ok here, the id just needs to be unique per
1117 	 * filter.
1118 	 */
1119 	lockdep_assert_held(&filter->notify_lock);
1120 	return filter->notif->next_id++;
1121 }
1122 
seccomp_handle_addfd(struct seccomp_kaddfd * addfd,struct seccomp_knotif * n)1123 static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n)
1124 {
1125 	int fd;
1126 
1127 	/*
1128 	 * Remove the notification, and reset the list pointers, indicating
1129 	 * that it has been handled.
1130 	 */
1131 	list_del_init(&addfd->list);
1132 	if (!addfd->setfd)
1133 		fd = receive_fd(addfd->file, NULL, addfd->flags);
1134 	else
1135 		fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags);
1136 	addfd->ret = fd;
1137 
1138 	if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) {
1139 		/* If we fail reset and return an error to the notifier */
1140 		if (fd < 0) {
1141 			n->state = SECCOMP_NOTIFY_SENT;
1142 		} else {
1143 			/* Return the FD we just added */
1144 			n->flags = 0;
1145 			n->error = 0;
1146 			n->val = fd;
1147 		}
1148 	}
1149 
1150 	/*
1151 	 * Mark the notification as completed. From this point, addfd mem
1152 	 * might be invalidated and we can't safely read it anymore.
1153 	 */
1154 	complete(&addfd->completion);
1155 }
1156 
should_sleep_killable(struct seccomp_filter * match,struct seccomp_knotif * n)1157 static bool should_sleep_killable(struct seccomp_filter *match,
1158 				  struct seccomp_knotif *n)
1159 {
1160 	return match->wait_killable_recv && n->state >= SECCOMP_NOTIFY_SENT;
1161 }
1162 
seccomp_do_user_notification(int this_syscall,struct seccomp_filter * match,const struct seccomp_data * sd)1163 static int seccomp_do_user_notification(int this_syscall,
1164 					struct seccomp_filter *match,
1165 					const struct seccomp_data *sd)
1166 {
1167 	int err;
1168 	u32 flags = 0;
1169 	long ret = 0;
1170 	struct seccomp_knotif n = {};
1171 	struct seccomp_kaddfd *addfd, *tmp;
1172 
1173 	mutex_lock(&match->notify_lock);
1174 	err = -ENOSYS;
1175 	if (!match->notif)
1176 		goto out;
1177 
1178 	n.task = current;
1179 	n.state = SECCOMP_NOTIFY_INIT;
1180 	n.data = sd;
1181 	n.id = seccomp_next_notify_id(match);
1182 	init_completion(&n.ready);
1183 	list_add_tail(&n.list, &match->notif->notifications);
1184 	INIT_LIST_HEAD(&n.addfd);
1185 
1186 	atomic_inc(&match->notif->requests);
1187 	if (match->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1188 		wake_up_poll_on_current_cpu(&match->wqh, EPOLLIN | EPOLLRDNORM);
1189 	else
1190 		wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
1191 
1192 	/*
1193 	 * This is where we wait for a reply from userspace.
1194 	 */
1195 	do {
1196 		bool wait_killable = should_sleep_killable(match, &n);
1197 
1198 		mutex_unlock(&match->notify_lock);
1199 		if (wait_killable)
1200 			err = wait_for_completion_killable(&n.ready);
1201 		else
1202 			err = wait_for_completion_interruptible(&n.ready);
1203 		mutex_lock(&match->notify_lock);
1204 
1205 		if (err != 0) {
1206 			/*
1207 			 * Check to see whether we should switch to wait
1208 			 * killable. Only return the interrupted error if not.
1209 			 */
1210 			if (!(!wait_killable && should_sleep_killable(match, &n)))
1211 				goto interrupted;
1212 		}
1213 
1214 		addfd = list_first_entry_or_null(&n.addfd,
1215 						 struct seccomp_kaddfd, list);
1216 		/* Check if we were woken up by a addfd message */
1217 		if (addfd)
1218 			seccomp_handle_addfd(addfd, &n);
1219 
1220 	}  while (n.state != SECCOMP_NOTIFY_REPLIED);
1221 
1222 	ret = n.val;
1223 	err = n.error;
1224 	flags = n.flags;
1225 
1226 interrupted:
1227 	/* If there were any pending addfd calls, clear them out */
1228 	list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
1229 		/* The process went away before we got a chance to handle it */
1230 		addfd->ret = -ESRCH;
1231 		list_del_init(&addfd->list);
1232 		complete(&addfd->completion);
1233 	}
1234 
1235 	/*
1236 	 * Note that it's possible the listener died in between the time when
1237 	 * we were notified of a response (or a signal) and when we were able to
1238 	 * re-acquire the lock, so only delete from the list if the
1239 	 * notification actually exists.
1240 	 *
1241 	 * Also note that this test is only valid because there's no way to
1242 	 * *reattach* to a notifier right now. If one is added, we'll need to
1243 	 * keep track of the notif itself and make sure they match here.
1244 	 */
1245 	if (match->notif)
1246 		list_del(&n.list);
1247 out:
1248 	mutex_unlock(&match->notify_lock);
1249 
1250 	/* Userspace requests to continue the syscall. */
1251 	if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1252 		return 0;
1253 
1254 	syscall_set_return_value(current, current_pt_regs(),
1255 				 err, ret);
1256 	return -1;
1257 }
1258 
__seccomp_filter(int this_syscall,const bool recheck_after_trace)1259 static int __seccomp_filter(int this_syscall, const bool recheck_after_trace)
1260 {
1261 	u32 filter_ret, action;
1262 	struct seccomp_data sd;
1263 	struct seccomp_filter *match = NULL;
1264 	int data;
1265 
1266 	/*
1267 	 * Make sure that any changes to mode from another thread have
1268 	 * been seen after SYSCALL_WORK_SECCOMP was seen.
1269 	 */
1270 	smp_rmb();
1271 
1272 	populate_seccomp_data(&sd);
1273 
1274 	filter_ret = seccomp_run_filters(&sd, &match);
1275 	data = filter_ret & SECCOMP_RET_DATA;
1276 	action = filter_ret & SECCOMP_RET_ACTION_FULL;
1277 
1278 	switch (action) {
1279 	case SECCOMP_RET_ERRNO:
1280 		/* Set low-order bits as an errno, capped at MAX_ERRNO. */
1281 		if (data > MAX_ERRNO)
1282 			data = MAX_ERRNO;
1283 		syscall_set_return_value(current, current_pt_regs(),
1284 					 -data, 0);
1285 		goto skip;
1286 
1287 	case SECCOMP_RET_TRAP:
1288 		/* Show the handler the original registers. */
1289 		syscall_rollback(current, current_pt_regs());
1290 		/* Let the filter pass back 16 bits of data. */
1291 		force_sig_seccomp(this_syscall, data, false);
1292 		goto skip;
1293 
1294 	case SECCOMP_RET_TRACE:
1295 		/* We've been put in this state by the ptracer already. */
1296 		if (recheck_after_trace)
1297 			return 0;
1298 
1299 		/* ENOSYS these calls if there is no tracer attached. */
1300 		if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
1301 			syscall_set_return_value(current,
1302 						 current_pt_regs(),
1303 						 -ENOSYS, 0);
1304 			goto skip;
1305 		}
1306 
1307 		/* Allow the BPF to provide the event message */
1308 		ptrace_event(PTRACE_EVENT_SECCOMP, data);
1309 		/*
1310 		 * The delivery of a fatal signal during event
1311 		 * notification may silently skip tracer notification,
1312 		 * which could leave us with a potentially unmodified
1313 		 * syscall that the tracer would have liked to have
1314 		 * changed. Since the process is about to die, we just
1315 		 * force the syscall to be skipped and let the signal
1316 		 * kill the process and correctly handle any tracer exit
1317 		 * notifications.
1318 		 */
1319 		if (fatal_signal_pending(current))
1320 			goto skip;
1321 		/* Check if the tracer forced the syscall to be skipped. */
1322 		this_syscall = syscall_get_nr(current, current_pt_regs());
1323 		if (this_syscall < 0)
1324 			goto skip;
1325 
1326 		/*
1327 		 * Recheck the syscall, since it may have changed. This
1328 		 * intentionally uses a NULL struct seccomp_data to force
1329 		 * a reload of all registers. This does not goto skip since
1330 		 * a skip would have already been reported.
1331 		 */
1332 		if (__seccomp_filter(this_syscall, true))
1333 			return -1;
1334 
1335 		return 0;
1336 
1337 	case SECCOMP_RET_USER_NOTIF:
1338 		if (seccomp_do_user_notification(this_syscall, match, &sd))
1339 			goto skip;
1340 
1341 		return 0;
1342 
1343 	case SECCOMP_RET_LOG:
1344 		seccomp_log(this_syscall, 0, action, true);
1345 		return 0;
1346 
1347 	case SECCOMP_RET_ALLOW:
1348 		/*
1349 		 * Note that the "match" filter will always be NULL for
1350 		 * this action since SECCOMP_RET_ALLOW is the starting
1351 		 * state in seccomp_run_filters().
1352 		 */
1353 		return 0;
1354 
1355 	case SECCOMP_RET_KILL_THREAD:
1356 	case SECCOMP_RET_KILL_PROCESS:
1357 	default:
1358 		current->seccomp.mode = SECCOMP_MODE_DEAD;
1359 		seccomp_log(this_syscall, SIGSYS, action, true);
1360 		/* Dump core only if this is the last remaining thread. */
1361 		if (action != SECCOMP_RET_KILL_THREAD ||
1362 		    (atomic_read(&current->signal->live) == 1)) {
1363 			/* Show the original registers in the dump. */
1364 			syscall_rollback(current, current_pt_regs());
1365 			/* Trigger a coredump with SIGSYS */
1366 			force_sig_seccomp(this_syscall, data, true);
1367 		} else {
1368 			do_exit(SIGSYS);
1369 		}
1370 		return -1; /* skip the syscall go directly to signal handling */
1371 	}
1372 
1373 	unreachable();
1374 
1375 skip:
1376 	seccomp_log(this_syscall, 0, action, match ? match->log : false);
1377 	return -1;
1378 }
1379 #else
__seccomp_filter(int this_syscall,const bool recheck_after_trace)1380 static int __seccomp_filter(int this_syscall, const bool recheck_after_trace)
1381 {
1382 	BUG();
1383 
1384 	return -1;
1385 }
1386 #endif
1387 
__secure_computing(void)1388 int __secure_computing(void)
1389 {
1390 	int mode = current->seccomp.mode;
1391 	int this_syscall;
1392 
1393 	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1394 	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1395 		return 0;
1396 
1397 	this_syscall = syscall_get_nr(current, current_pt_regs());
1398 
1399 	switch (mode) {
1400 	case SECCOMP_MODE_STRICT:
1401 		__secure_computing_strict(this_syscall);  /* may call do_exit */
1402 		return 0;
1403 	case SECCOMP_MODE_FILTER:
1404 		return __seccomp_filter(this_syscall, false);
1405 	/* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */
1406 	case SECCOMP_MODE_DEAD:
1407 		WARN_ON_ONCE(1);
1408 		do_exit(SIGKILL);
1409 		return -1;
1410 	default:
1411 		BUG();
1412 	}
1413 }
1414 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
1415 
prctl_get_seccomp(void)1416 long prctl_get_seccomp(void)
1417 {
1418 	return current->seccomp.mode;
1419 }
1420 
1421 /**
1422  * seccomp_set_mode_strict: internal function for setting strict seccomp
1423  *
1424  * Once current->seccomp.mode is non-zero, it may not be changed.
1425  *
1426  * Returns 0 on success or -EINVAL on failure.
1427  */
seccomp_set_mode_strict(void)1428 static long seccomp_set_mode_strict(void)
1429 {
1430 	const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
1431 	long ret = -EINVAL;
1432 
1433 	spin_lock_irq(&current->sighand->siglock);
1434 
1435 	if (!seccomp_may_assign_mode(seccomp_mode))
1436 		goto out;
1437 
1438 #ifdef TIF_NOTSC
1439 	disable_TSC();
1440 #endif
1441 	seccomp_assign_mode(current, seccomp_mode, 0);
1442 	ret = 0;
1443 
1444 out:
1445 	spin_unlock_irq(&current->sighand->siglock);
1446 
1447 	return ret;
1448 }
1449 
1450 #ifdef CONFIG_SECCOMP_FILTER
seccomp_notify_free(struct seccomp_filter * filter)1451 static void seccomp_notify_free(struct seccomp_filter *filter)
1452 {
1453 	kfree(filter->notif);
1454 	filter->notif = NULL;
1455 }
1456 
seccomp_notify_detach(struct seccomp_filter * filter)1457 static void seccomp_notify_detach(struct seccomp_filter *filter)
1458 {
1459 	struct seccomp_knotif *knotif;
1460 
1461 	if (!filter)
1462 		return;
1463 
1464 	mutex_lock(&filter->notify_lock);
1465 
1466 	/*
1467 	 * If this file is being closed because e.g. the task who owned it
1468 	 * died, let's wake everyone up who was waiting on us.
1469 	 */
1470 	list_for_each_entry(knotif, &filter->notif->notifications, list) {
1471 		if (knotif->state == SECCOMP_NOTIFY_REPLIED)
1472 			continue;
1473 
1474 		knotif->state = SECCOMP_NOTIFY_REPLIED;
1475 		knotif->error = -ENOSYS;
1476 		knotif->val = 0;
1477 
1478 		/*
1479 		 * We do not need to wake up any pending addfd messages, as
1480 		 * the notifier will do that for us, as this just looks
1481 		 * like a standard reply.
1482 		 */
1483 		complete(&knotif->ready);
1484 	}
1485 
1486 	seccomp_notify_free(filter);
1487 	mutex_unlock(&filter->notify_lock);
1488 }
1489 
seccomp_notify_release(struct inode * inode,struct file * file)1490 static int seccomp_notify_release(struct inode *inode, struct file *file)
1491 {
1492 	struct seccomp_filter *filter = file->private_data;
1493 
1494 	seccomp_notify_detach(filter);
1495 	__put_seccomp_filter(filter);
1496 	return 0;
1497 }
1498 
1499 /* must be called with notif_lock held */
1500 static inline struct seccomp_knotif *
find_notification(struct seccomp_filter * filter,u64 id)1501 find_notification(struct seccomp_filter *filter, u64 id)
1502 {
1503 	struct seccomp_knotif *cur;
1504 
1505 	lockdep_assert_held(&filter->notify_lock);
1506 
1507 	list_for_each_entry(cur, &filter->notif->notifications, list) {
1508 		if (cur->id == id)
1509 			return cur;
1510 	}
1511 
1512 	return NULL;
1513 }
1514 
recv_wake_function(wait_queue_entry_t * wait,unsigned int mode,int sync,void * key)1515 static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync,
1516 				  void *key)
1517 {
1518 	/* Avoid a wakeup if event not interesting for us. */
1519 	if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP)))
1520 		return 0;
1521 	return autoremove_wake_function(wait, mode, sync, key);
1522 }
1523 
recv_wait_event(struct seccomp_filter * filter)1524 static int recv_wait_event(struct seccomp_filter *filter)
1525 {
1526 	DEFINE_WAIT_FUNC(wait, recv_wake_function);
1527 	int ret;
1528 
1529 	if (refcount_read(&filter->users) == 0)
1530 		return 0;
1531 
1532 	if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
1533 		return 0;
1534 
1535 	for (;;) {
1536 		ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE);
1537 
1538 		if (atomic_dec_if_positive(&filter->notif->requests) >= 0)
1539 			break;
1540 		if (refcount_read(&filter->users) == 0)
1541 			break;
1542 
1543 		if (ret)
1544 			return ret;
1545 
1546 		schedule();
1547 	}
1548 	finish_wait(&filter->wqh, &wait);
1549 	return 0;
1550 }
1551 
seccomp_notify_recv(struct seccomp_filter * filter,void __user * buf)1552 static long seccomp_notify_recv(struct seccomp_filter *filter,
1553 				void __user *buf)
1554 {
1555 	struct seccomp_knotif *knotif = NULL, *cur;
1556 	struct seccomp_notif unotif;
1557 	ssize_t ret;
1558 
1559 	/* Verify that we're not given garbage to keep struct extensible. */
1560 	ret = check_zeroed_user(buf, sizeof(unotif));
1561 	if (ret < 0)
1562 		return ret;
1563 	if (!ret)
1564 		return -EINVAL;
1565 
1566 	memset(&unotif, 0, sizeof(unotif));
1567 
1568 	ret = recv_wait_event(filter);
1569 	if (ret < 0)
1570 		return ret;
1571 
1572 	mutex_lock(&filter->notify_lock);
1573 	list_for_each_entry(cur, &filter->notif->notifications, list) {
1574 		if (cur->state == SECCOMP_NOTIFY_INIT) {
1575 			knotif = cur;
1576 			break;
1577 		}
1578 	}
1579 
1580 	/*
1581 	 * If we didn't find a notification, it could be that the task was
1582 	 * interrupted by a fatal signal between the time we were woken and
1583 	 * when we were able to acquire the rw lock.
1584 	 */
1585 	if (!knotif) {
1586 		ret = -ENOENT;
1587 		goto out;
1588 	}
1589 
1590 	unotif.id = knotif->id;
1591 	unotif.pid = task_pid_vnr(knotif->task);
1592 	unotif.data = *(knotif->data);
1593 
1594 	knotif->state = SECCOMP_NOTIFY_SENT;
1595 	wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM);
1596 	ret = 0;
1597 out:
1598 	mutex_unlock(&filter->notify_lock);
1599 
1600 	if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
1601 		ret = -EFAULT;
1602 
1603 		/*
1604 		 * Userspace screwed up. To make sure that we keep this
1605 		 * notification alive, let's reset it back to INIT. It
1606 		 * may have died when we released the lock, so we need to make
1607 		 * sure it's still around.
1608 		 */
1609 		mutex_lock(&filter->notify_lock);
1610 		knotif = find_notification(filter, unotif.id);
1611 		if (knotif) {
1612 			/* Reset the process to make sure it's not stuck */
1613 			if (should_sleep_killable(filter, knotif))
1614 				complete(&knotif->ready);
1615 			knotif->state = SECCOMP_NOTIFY_INIT;
1616 			atomic_inc(&filter->notif->requests);
1617 			wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM);
1618 		}
1619 		mutex_unlock(&filter->notify_lock);
1620 	}
1621 
1622 	return ret;
1623 }
1624 
seccomp_notify_send(struct seccomp_filter * filter,void __user * buf)1625 static long seccomp_notify_send(struct seccomp_filter *filter,
1626 				void __user *buf)
1627 {
1628 	struct seccomp_notif_resp resp = {};
1629 	struct seccomp_knotif *knotif;
1630 	long ret;
1631 
1632 	if (copy_from_user(&resp, buf, sizeof(resp)))
1633 		return -EFAULT;
1634 
1635 	if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1636 		return -EINVAL;
1637 
1638 	if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) &&
1639 	    (resp.error || resp.val))
1640 		return -EINVAL;
1641 
1642 	ret = mutex_lock_interruptible(&filter->notify_lock);
1643 	if (ret < 0)
1644 		return ret;
1645 
1646 	knotif = find_notification(filter, resp.id);
1647 	if (!knotif) {
1648 		ret = -ENOENT;
1649 		goto out;
1650 	}
1651 
1652 	/* Allow exactly one reply. */
1653 	if (knotif->state != SECCOMP_NOTIFY_SENT) {
1654 		ret = -EINPROGRESS;
1655 		goto out;
1656 	}
1657 
1658 	ret = 0;
1659 	knotif->state = SECCOMP_NOTIFY_REPLIED;
1660 	knotif->error = resp.error;
1661 	knotif->val = resp.val;
1662 	knotif->flags = resp.flags;
1663 	if (filter->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1664 		complete_on_current_cpu(&knotif->ready);
1665 	else
1666 		complete(&knotif->ready);
1667 out:
1668 	mutex_unlock(&filter->notify_lock);
1669 	return ret;
1670 }
1671 
seccomp_notify_id_valid(struct seccomp_filter * filter,void __user * buf)1672 static long seccomp_notify_id_valid(struct seccomp_filter *filter,
1673 				    void __user *buf)
1674 {
1675 	struct seccomp_knotif *knotif;
1676 	u64 id;
1677 	long ret;
1678 
1679 	if (copy_from_user(&id, buf, sizeof(id)))
1680 		return -EFAULT;
1681 
1682 	ret = mutex_lock_interruptible(&filter->notify_lock);
1683 	if (ret < 0)
1684 		return ret;
1685 
1686 	knotif = find_notification(filter, id);
1687 	if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
1688 		ret = 0;
1689 	else
1690 		ret = -ENOENT;
1691 
1692 	mutex_unlock(&filter->notify_lock);
1693 	return ret;
1694 }
1695 
seccomp_notify_set_flags(struct seccomp_filter * filter,unsigned long flags)1696 static long seccomp_notify_set_flags(struct seccomp_filter *filter,
1697 				    unsigned long flags)
1698 {
1699 	long ret;
1700 
1701 	if (flags & ~SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP)
1702 		return -EINVAL;
1703 
1704 	ret = mutex_lock_interruptible(&filter->notify_lock);
1705 	if (ret < 0)
1706 		return ret;
1707 	filter->notif->flags = flags;
1708 	mutex_unlock(&filter->notify_lock);
1709 	return 0;
1710 }
1711 
seccomp_notify_addfd(struct seccomp_filter * filter,struct seccomp_notif_addfd __user * uaddfd,unsigned int size)1712 static long seccomp_notify_addfd(struct seccomp_filter *filter,
1713 				 struct seccomp_notif_addfd __user *uaddfd,
1714 				 unsigned int size)
1715 {
1716 	struct seccomp_notif_addfd addfd;
1717 	struct seccomp_knotif *knotif;
1718 	struct seccomp_kaddfd kaddfd;
1719 	int ret;
1720 
1721 	BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0);
1722 	BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST);
1723 
1724 	if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE)
1725 		return -EINVAL;
1726 
1727 	ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size);
1728 	if (ret)
1729 		return ret;
1730 
1731 	if (addfd.newfd_flags & ~O_CLOEXEC)
1732 		return -EINVAL;
1733 
1734 	if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND))
1735 		return -EINVAL;
1736 
1737 	if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
1738 		return -EINVAL;
1739 
1740 	kaddfd.file = fget(addfd.srcfd);
1741 	if (!kaddfd.file)
1742 		return -EBADF;
1743 
1744 	kaddfd.ioctl_flags = addfd.flags;
1745 	kaddfd.flags = addfd.newfd_flags;
1746 	kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD;
1747 	kaddfd.fd = addfd.newfd;
1748 	init_completion(&kaddfd.completion);
1749 
1750 	ret = mutex_lock_interruptible(&filter->notify_lock);
1751 	if (ret < 0)
1752 		goto out;
1753 
1754 	knotif = find_notification(filter, addfd.id);
1755 	if (!knotif) {
1756 		ret = -ENOENT;
1757 		goto out_unlock;
1758 	}
1759 
1760 	/*
1761 	 * We do not want to allow for FD injection to occur before the
1762 	 * notification has been picked up by a userspace handler, or after
1763 	 * the notification has been replied to.
1764 	 */
1765 	if (knotif->state != SECCOMP_NOTIFY_SENT) {
1766 		ret = -EINPROGRESS;
1767 		goto out_unlock;
1768 	}
1769 
1770 	if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) {
1771 		/*
1772 		 * Disallow queuing an atomic addfd + send reply while there are
1773 		 * some addfd requests still to process.
1774 		 *
1775 		 * There is no clear reason to support it and allows us to keep
1776 		 * the loop on the other side straight-forward.
1777 		 */
1778 		if (!list_empty(&knotif->addfd)) {
1779 			ret = -EBUSY;
1780 			goto out_unlock;
1781 		}
1782 
1783 		/* Allow exactly only one reply */
1784 		knotif->state = SECCOMP_NOTIFY_REPLIED;
1785 	}
1786 
1787 	list_add(&kaddfd.list, &knotif->addfd);
1788 	complete(&knotif->ready);
1789 	mutex_unlock(&filter->notify_lock);
1790 
1791 	/* Now we wait for it to be processed or be interrupted */
1792 	ret = wait_for_completion_interruptible(&kaddfd.completion);
1793 	if (ret == 0) {
1794 		/*
1795 		 * We had a successful completion. The other side has already
1796 		 * removed us from the addfd queue, and
1797 		 * wait_for_completion_interruptible has a memory barrier upon
1798 		 * success that lets us read this value directly without
1799 		 * locking.
1800 		 */
1801 		ret = kaddfd.ret;
1802 		goto out;
1803 	}
1804 
1805 	mutex_lock(&filter->notify_lock);
1806 	/*
1807 	 * Even though we were woken up by a signal and not a successful
1808 	 * completion, a completion may have happened in the mean time.
1809 	 *
1810 	 * We need to check again if the addfd request has been handled,
1811 	 * and if not, we will remove it from the queue.
1812 	 */
1813 	if (list_empty(&kaddfd.list))
1814 		ret = kaddfd.ret;
1815 	else
1816 		list_del(&kaddfd.list);
1817 
1818 out_unlock:
1819 	mutex_unlock(&filter->notify_lock);
1820 out:
1821 	fput(kaddfd.file);
1822 
1823 	return ret;
1824 }
1825 
seccomp_notify_ioctl(struct file * file,unsigned int cmd,unsigned long arg)1826 static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
1827 				 unsigned long arg)
1828 {
1829 	struct seccomp_filter *filter = file->private_data;
1830 	void __user *buf = (void __user *)arg;
1831 
1832 	/* Fixed-size ioctls */
1833 	switch (cmd) {
1834 	case SECCOMP_IOCTL_NOTIF_RECV:
1835 		return seccomp_notify_recv(filter, buf);
1836 	case SECCOMP_IOCTL_NOTIF_SEND:
1837 		return seccomp_notify_send(filter, buf);
1838 	case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
1839 	case SECCOMP_IOCTL_NOTIF_ID_VALID:
1840 		return seccomp_notify_id_valid(filter, buf);
1841 	case SECCOMP_IOCTL_NOTIF_SET_FLAGS:
1842 		return seccomp_notify_set_flags(filter, arg);
1843 	}
1844 
1845 	/* Extensible Argument ioctls */
1846 #define EA_IOCTL(cmd)	((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
1847 	switch (EA_IOCTL(cmd)) {
1848 	case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
1849 		return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
1850 	default:
1851 		return -EINVAL;
1852 	}
1853 }
1854 
seccomp_notify_poll(struct file * file,struct poll_table_struct * poll_tab)1855 static __poll_t seccomp_notify_poll(struct file *file,
1856 				    struct poll_table_struct *poll_tab)
1857 {
1858 	struct seccomp_filter *filter = file->private_data;
1859 	__poll_t ret = 0;
1860 	struct seccomp_knotif *cur;
1861 
1862 	poll_wait(file, &filter->wqh, poll_tab);
1863 
1864 	if (mutex_lock_interruptible(&filter->notify_lock) < 0)
1865 		return EPOLLERR;
1866 
1867 	list_for_each_entry(cur, &filter->notif->notifications, list) {
1868 		if (cur->state == SECCOMP_NOTIFY_INIT)
1869 			ret |= EPOLLIN | EPOLLRDNORM;
1870 		if (cur->state == SECCOMP_NOTIFY_SENT)
1871 			ret |= EPOLLOUT | EPOLLWRNORM;
1872 		if ((ret & EPOLLIN) && (ret & EPOLLOUT))
1873 			break;
1874 	}
1875 
1876 	mutex_unlock(&filter->notify_lock);
1877 
1878 	if (refcount_read(&filter->users) == 0)
1879 		ret |= EPOLLHUP;
1880 
1881 	return ret;
1882 }
1883 
1884 static const struct file_operations seccomp_notify_ops = {
1885 	.poll = seccomp_notify_poll,
1886 	.release = seccomp_notify_release,
1887 	.unlocked_ioctl = seccomp_notify_ioctl,
1888 	.compat_ioctl = seccomp_notify_ioctl,
1889 };
1890 
init_listener(struct seccomp_filter * filter)1891 static struct file *init_listener(struct seccomp_filter *filter)
1892 {
1893 	struct file *ret;
1894 
1895 	ret = ERR_PTR(-ENOMEM);
1896 	filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
1897 	if (!filter->notif)
1898 		goto out;
1899 
1900 	filter->notif->next_id = get_random_u64();
1901 	INIT_LIST_HEAD(&filter->notif->notifications);
1902 
1903 	ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
1904 				 filter, O_RDWR);
1905 	if (IS_ERR(ret))
1906 		goto out_notif;
1907 
1908 	/* The file has a reference to it now */
1909 	__get_seccomp_filter(filter);
1910 
1911 out_notif:
1912 	if (IS_ERR(ret))
1913 		seccomp_notify_free(filter);
1914 out:
1915 	return ret;
1916 }
1917 
1918 /*
1919  * Does @new_child have a listener while an ancestor also has a listener?
1920  * If so, we'll want to reject this filter.
1921  * This only has to be tested for the current process, even in the TSYNC case,
1922  * because TSYNC installs @child with the same parent on all threads.
1923  * Note that @new_child is not hooked up to its parent at this point yet, so
1924  * we use current->seccomp.filter.
1925  */
has_duplicate_listener(struct seccomp_filter * new_child)1926 static bool has_duplicate_listener(struct seccomp_filter *new_child)
1927 {
1928 	struct seccomp_filter *cur;
1929 
1930 	/* must be protected against concurrent TSYNC */
1931 	lockdep_assert_held(&current->sighand->siglock);
1932 
1933 	if (!new_child->notif)
1934 		return false;
1935 	for (cur = current->seccomp.filter; cur; cur = cur->prev) {
1936 		if (cur->notif)
1937 			return true;
1938 	}
1939 
1940 	return false;
1941 }
1942 
1943 /**
1944  * seccomp_set_mode_filter: internal function for setting seccomp filter
1945  * @flags:  flags to change filter behavior
1946  * @filter: struct sock_fprog containing filter
1947  *
1948  * This function may be called repeatedly to install additional filters.
1949  * Every filter successfully installed will be evaluated (in reverse order)
1950  * for each system call the task makes.
1951  *
1952  * Once current->seccomp.mode is non-zero, it may not be changed.
1953  *
1954  * Returns 0 on success or -EINVAL on failure.
1955  */
seccomp_set_mode_filter(unsigned int flags,const char __user * filter)1956 static long seccomp_set_mode_filter(unsigned int flags,
1957 				    const char __user *filter)
1958 {
1959 	const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
1960 	struct seccomp_filter *prepared = NULL;
1961 	long ret = -EINVAL;
1962 	int listener = -1;
1963 	struct file *listener_f = NULL;
1964 
1965 	/* Validate flags. */
1966 	if (flags & ~SECCOMP_FILTER_FLAG_MASK)
1967 		return -EINVAL;
1968 
1969 	/*
1970 	 * In the successful case, NEW_LISTENER returns the new listener fd.
1971 	 * But in the failure case, TSYNC returns the thread that died. If you
1972 	 * combine these two flags, there's no way to tell whether something
1973 	 * succeeded or failed. So, let's disallow this combination if the user
1974 	 * has not explicitly requested no errors from TSYNC.
1975 	 */
1976 	if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
1977 	    (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) &&
1978 	    ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0))
1979 		return -EINVAL;
1980 
1981 	/*
1982 	 * The SECCOMP_FILTER_FLAG_WAIT_KILLABLE_SENT flag doesn't make sense
1983 	 * without the SECCOMP_FILTER_FLAG_NEW_LISTENER flag.
1984 	 */
1985 	if ((flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) &&
1986 	    ((flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) == 0))
1987 		return -EINVAL;
1988 
1989 	/* Prepare the new filter before holding any locks. */
1990 	prepared = seccomp_prepare_user_filter(filter);
1991 	if (IS_ERR(prepared))
1992 		return PTR_ERR(prepared);
1993 
1994 	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1995 		listener = get_unused_fd_flags(O_CLOEXEC);
1996 		if (listener < 0) {
1997 			ret = listener;
1998 			goto out_free;
1999 		}
2000 
2001 		listener_f = init_listener(prepared);
2002 		if (IS_ERR(listener_f)) {
2003 			put_unused_fd(listener);
2004 			ret = PTR_ERR(listener_f);
2005 			goto out_free;
2006 		}
2007 	}
2008 
2009 	/*
2010 	 * Make sure we cannot change seccomp or nnp state via TSYNC
2011 	 * while another thread is in the middle of calling exec.
2012 	 */
2013 	if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
2014 	    mutex_lock_killable(&current->signal->cred_guard_mutex))
2015 		goto out_put_fd;
2016 
2017 	spin_lock_irq(&current->sighand->siglock);
2018 
2019 	if (!seccomp_may_assign_mode(seccomp_mode))
2020 		goto out;
2021 
2022 	if (has_duplicate_listener(prepared)) {
2023 		ret = -EBUSY;
2024 		goto out;
2025 	}
2026 
2027 	ret = seccomp_attach_filter(flags, prepared);
2028 	if (ret)
2029 		goto out;
2030 	/* Do not free the successfully attached filter. */
2031 	prepared = NULL;
2032 
2033 	seccomp_assign_mode(current, seccomp_mode, flags);
2034 out:
2035 	spin_unlock_irq(&current->sighand->siglock);
2036 	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
2037 		mutex_unlock(&current->signal->cred_guard_mutex);
2038 out_put_fd:
2039 	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
2040 		if (ret) {
2041 			listener_f->private_data = NULL;
2042 			fput(listener_f);
2043 			put_unused_fd(listener);
2044 			seccomp_notify_detach(prepared);
2045 		} else {
2046 			fd_install(listener, listener_f);
2047 			ret = listener;
2048 		}
2049 	}
2050 out_free:
2051 	seccomp_filter_free(prepared);
2052 	return ret;
2053 }
2054 #else
seccomp_set_mode_filter(unsigned int flags,const char __user * filter)2055 static inline long seccomp_set_mode_filter(unsigned int flags,
2056 					   const char __user *filter)
2057 {
2058 	return -EINVAL;
2059 }
2060 #endif
2061 
seccomp_get_action_avail(const char __user * uaction)2062 static long seccomp_get_action_avail(const char __user *uaction)
2063 {
2064 	u32 action;
2065 
2066 	if (copy_from_user(&action, uaction, sizeof(action)))
2067 		return -EFAULT;
2068 
2069 	switch (action) {
2070 	case SECCOMP_RET_KILL_PROCESS:
2071 	case SECCOMP_RET_KILL_THREAD:
2072 	case SECCOMP_RET_TRAP:
2073 	case SECCOMP_RET_ERRNO:
2074 	case SECCOMP_RET_USER_NOTIF:
2075 	case SECCOMP_RET_TRACE:
2076 	case SECCOMP_RET_LOG:
2077 	case SECCOMP_RET_ALLOW:
2078 		break;
2079 	default:
2080 		return -EOPNOTSUPP;
2081 	}
2082 
2083 	return 0;
2084 }
2085 
seccomp_get_notif_sizes(void __user * usizes)2086 static long seccomp_get_notif_sizes(void __user *usizes)
2087 {
2088 	struct seccomp_notif_sizes sizes = {
2089 		.seccomp_notif = sizeof(struct seccomp_notif),
2090 		.seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
2091 		.seccomp_data = sizeof(struct seccomp_data),
2092 	};
2093 
2094 	if (copy_to_user(usizes, &sizes, sizeof(sizes)))
2095 		return -EFAULT;
2096 
2097 	return 0;
2098 }
2099 
2100 /* Common entry point for both prctl and syscall. */
do_seccomp(unsigned int op,unsigned int flags,void __user * uargs)2101 static long do_seccomp(unsigned int op, unsigned int flags,
2102 		       void __user *uargs)
2103 {
2104 	switch (op) {
2105 	case SECCOMP_SET_MODE_STRICT:
2106 		if (flags != 0 || uargs != NULL)
2107 			return -EINVAL;
2108 		return seccomp_set_mode_strict();
2109 	case SECCOMP_SET_MODE_FILTER:
2110 		return seccomp_set_mode_filter(flags, uargs);
2111 	case SECCOMP_GET_ACTION_AVAIL:
2112 		if (flags != 0)
2113 			return -EINVAL;
2114 
2115 		return seccomp_get_action_avail(uargs);
2116 	case SECCOMP_GET_NOTIF_SIZES:
2117 		if (flags != 0)
2118 			return -EINVAL;
2119 
2120 		return seccomp_get_notif_sizes(uargs);
2121 	default:
2122 		return -EINVAL;
2123 	}
2124 }
2125 
SYSCALL_DEFINE3(seccomp,unsigned int,op,unsigned int,flags,void __user *,uargs)2126 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
2127 			 void __user *, uargs)
2128 {
2129 	return do_seccomp(op, flags, uargs);
2130 }
2131 
2132 /**
2133  * prctl_set_seccomp: configures current->seccomp.mode
2134  * @seccomp_mode: requested mode to use
2135  * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
2136  *
2137  * Returns 0 on success or -EINVAL on failure.
2138  */
prctl_set_seccomp(unsigned long seccomp_mode,void __user * filter)2139 long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
2140 {
2141 	unsigned int op;
2142 	void __user *uargs;
2143 
2144 	switch (seccomp_mode) {
2145 	case SECCOMP_MODE_STRICT:
2146 		op = SECCOMP_SET_MODE_STRICT;
2147 		/*
2148 		 * Setting strict mode through prctl always ignored filter,
2149 		 * so make sure it is always NULL here to pass the internal
2150 		 * check in do_seccomp().
2151 		 */
2152 		uargs = NULL;
2153 		break;
2154 	case SECCOMP_MODE_FILTER:
2155 		op = SECCOMP_SET_MODE_FILTER;
2156 		uargs = filter;
2157 		break;
2158 	default:
2159 		return -EINVAL;
2160 	}
2161 
2162 	/* prctl interface doesn't have flags, so they are always zero. */
2163 	return do_seccomp(op, 0, uargs);
2164 }
2165 
2166 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
get_nth_filter(struct task_struct * task,unsigned long filter_off)2167 static struct seccomp_filter *get_nth_filter(struct task_struct *task,
2168 					     unsigned long filter_off)
2169 {
2170 	struct seccomp_filter *orig, *filter;
2171 	unsigned long count;
2172 
2173 	/*
2174 	 * Note: this is only correct because the caller should be the (ptrace)
2175 	 * tracer of the task, otherwise lock_task_sighand is needed.
2176 	 */
2177 	spin_lock_irq(&task->sighand->siglock);
2178 
2179 	if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
2180 		spin_unlock_irq(&task->sighand->siglock);
2181 		return ERR_PTR(-EINVAL);
2182 	}
2183 
2184 	orig = task->seccomp.filter;
2185 	__get_seccomp_filter(orig);
2186 	spin_unlock_irq(&task->sighand->siglock);
2187 
2188 	count = 0;
2189 	for (filter = orig; filter; filter = filter->prev)
2190 		count++;
2191 
2192 	if (filter_off >= count) {
2193 		filter = ERR_PTR(-ENOENT);
2194 		goto out;
2195 	}
2196 
2197 	count -= filter_off;
2198 	for (filter = orig; filter && count > 1; filter = filter->prev)
2199 		count--;
2200 
2201 	if (WARN_ON(count != 1 || !filter)) {
2202 		filter = ERR_PTR(-ENOENT);
2203 		goto out;
2204 	}
2205 
2206 	__get_seccomp_filter(filter);
2207 
2208 out:
2209 	__put_seccomp_filter(orig);
2210 	return filter;
2211 }
2212 
seccomp_get_filter(struct task_struct * task,unsigned long filter_off,void __user * data)2213 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
2214 			void __user *data)
2215 {
2216 	struct seccomp_filter *filter;
2217 	struct sock_fprog_kern *fprog;
2218 	long ret;
2219 
2220 	if (!capable(CAP_SYS_ADMIN) ||
2221 	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2222 		return -EACCES;
2223 	}
2224 
2225 	filter = get_nth_filter(task, filter_off);
2226 	if (IS_ERR(filter))
2227 		return PTR_ERR(filter);
2228 
2229 	fprog = filter->prog->orig_prog;
2230 	if (!fprog) {
2231 		/* This must be a new non-cBPF filter, since we save
2232 		 * every cBPF filter's orig_prog above when
2233 		 * CONFIG_CHECKPOINT_RESTORE is enabled.
2234 		 */
2235 		ret = -EMEDIUMTYPE;
2236 		goto out;
2237 	}
2238 
2239 	ret = fprog->len;
2240 	if (!data)
2241 		goto out;
2242 
2243 	if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
2244 		ret = -EFAULT;
2245 
2246 out:
2247 	__put_seccomp_filter(filter);
2248 	return ret;
2249 }
2250 
seccomp_get_metadata(struct task_struct * task,unsigned long size,void __user * data)2251 long seccomp_get_metadata(struct task_struct *task,
2252 			  unsigned long size, void __user *data)
2253 {
2254 	long ret;
2255 	struct seccomp_filter *filter;
2256 	struct seccomp_metadata kmd = {};
2257 
2258 	if (!capable(CAP_SYS_ADMIN) ||
2259 	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2260 		return -EACCES;
2261 	}
2262 
2263 	size = min_t(unsigned long, size, sizeof(kmd));
2264 
2265 	if (size < sizeof(kmd.filter_off))
2266 		return -EINVAL;
2267 
2268 	if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
2269 		return -EFAULT;
2270 
2271 	filter = get_nth_filter(task, kmd.filter_off);
2272 	if (IS_ERR(filter))
2273 		return PTR_ERR(filter);
2274 
2275 	if (filter->log)
2276 		kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
2277 
2278 	ret = size;
2279 	if (copy_to_user(data, &kmd, size))
2280 		ret = -EFAULT;
2281 
2282 	__put_seccomp_filter(filter);
2283 	return ret;
2284 }
2285 #endif
2286 
2287 #ifdef CONFIG_SYSCTL
2288 
2289 /* Human readable action names for friendly sysctl interaction */
2290 #define SECCOMP_RET_KILL_PROCESS_NAME	"kill_process"
2291 #define SECCOMP_RET_KILL_THREAD_NAME	"kill_thread"
2292 #define SECCOMP_RET_TRAP_NAME		"trap"
2293 #define SECCOMP_RET_ERRNO_NAME		"errno"
2294 #define SECCOMP_RET_USER_NOTIF_NAME	"user_notif"
2295 #define SECCOMP_RET_TRACE_NAME		"trace"
2296 #define SECCOMP_RET_LOG_NAME		"log"
2297 #define SECCOMP_RET_ALLOW_NAME		"allow"
2298 
2299 static const char seccomp_actions_avail[] =
2300 				SECCOMP_RET_KILL_PROCESS_NAME	" "
2301 				SECCOMP_RET_KILL_THREAD_NAME	" "
2302 				SECCOMP_RET_TRAP_NAME		" "
2303 				SECCOMP_RET_ERRNO_NAME		" "
2304 				SECCOMP_RET_USER_NOTIF_NAME     " "
2305 				SECCOMP_RET_TRACE_NAME		" "
2306 				SECCOMP_RET_LOG_NAME		" "
2307 				SECCOMP_RET_ALLOW_NAME;
2308 
2309 struct seccomp_log_name {
2310 	u32		log;
2311 	const char	*name;
2312 };
2313 
2314 static const struct seccomp_log_name seccomp_log_names[] = {
2315 	{ SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
2316 	{ SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
2317 	{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
2318 	{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
2319 	{ SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
2320 	{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
2321 	{ SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
2322 	{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
2323 	{ }
2324 };
2325 
seccomp_names_from_actions_logged(char * names,size_t size,u32 actions_logged,const char * sep)2326 static bool seccomp_names_from_actions_logged(char *names, size_t size,
2327 					      u32 actions_logged,
2328 					      const char *sep)
2329 {
2330 	const struct seccomp_log_name *cur;
2331 	bool append_sep = false;
2332 
2333 	for (cur = seccomp_log_names; cur->name && size; cur++) {
2334 		ssize_t ret;
2335 
2336 		if (!(actions_logged & cur->log))
2337 			continue;
2338 
2339 		if (append_sep) {
2340 			ret = strscpy(names, sep, size);
2341 			if (ret < 0)
2342 				return false;
2343 
2344 			names += ret;
2345 			size -= ret;
2346 		} else
2347 			append_sep = true;
2348 
2349 		ret = strscpy(names, cur->name, size);
2350 		if (ret < 0)
2351 			return false;
2352 
2353 		names += ret;
2354 		size -= ret;
2355 	}
2356 
2357 	return true;
2358 }
2359 
seccomp_action_logged_from_name(u32 * action_logged,const char * name)2360 static bool seccomp_action_logged_from_name(u32 *action_logged,
2361 					    const char *name)
2362 {
2363 	const struct seccomp_log_name *cur;
2364 
2365 	for (cur = seccomp_log_names; cur->name; cur++) {
2366 		if (!strcmp(cur->name, name)) {
2367 			*action_logged = cur->log;
2368 			return true;
2369 		}
2370 	}
2371 
2372 	return false;
2373 }
2374 
seccomp_actions_logged_from_names(u32 * actions_logged,char * names)2375 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
2376 {
2377 	char *name;
2378 
2379 	*actions_logged = 0;
2380 	while ((name = strsep(&names, " ")) && *name) {
2381 		u32 action_logged = 0;
2382 
2383 		if (!seccomp_action_logged_from_name(&action_logged, name))
2384 			return false;
2385 
2386 		*actions_logged |= action_logged;
2387 	}
2388 
2389 	return true;
2390 }
2391 
read_actions_logged(const struct ctl_table * ro_table,void * buffer,size_t * lenp,loff_t * ppos)2392 static int read_actions_logged(const struct ctl_table *ro_table, void *buffer,
2393 			       size_t *lenp, loff_t *ppos)
2394 {
2395 	char names[sizeof(seccomp_actions_avail)];
2396 	struct ctl_table table;
2397 
2398 	memset(names, 0, sizeof(names));
2399 
2400 	if (!seccomp_names_from_actions_logged(names, sizeof(names),
2401 					       seccomp_actions_logged, " "))
2402 		return -EINVAL;
2403 
2404 	table = *ro_table;
2405 	table.data = names;
2406 	table.maxlen = sizeof(names);
2407 	return proc_dostring(&table, 0, buffer, lenp, ppos);
2408 }
2409 
write_actions_logged(const struct ctl_table * ro_table,void * buffer,size_t * lenp,loff_t * ppos,u32 * actions_logged)2410 static int write_actions_logged(const struct ctl_table *ro_table, void *buffer,
2411 				size_t *lenp, loff_t *ppos, u32 *actions_logged)
2412 {
2413 	char names[sizeof(seccomp_actions_avail)];
2414 	struct ctl_table table;
2415 	int ret;
2416 
2417 	if (!capable(CAP_SYS_ADMIN))
2418 		return -EPERM;
2419 
2420 	memset(names, 0, sizeof(names));
2421 
2422 	table = *ro_table;
2423 	table.data = names;
2424 	table.maxlen = sizeof(names);
2425 	ret = proc_dostring(&table, 1, buffer, lenp, ppos);
2426 	if (ret)
2427 		return ret;
2428 
2429 	if (!seccomp_actions_logged_from_names(actions_logged, table.data))
2430 		return -EINVAL;
2431 
2432 	if (*actions_logged & SECCOMP_LOG_ALLOW)
2433 		return -EINVAL;
2434 
2435 	seccomp_actions_logged = *actions_logged;
2436 	return 0;
2437 }
2438 
audit_actions_logged(u32 actions_logged,u32 old_actions_logged,int ret)2439 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
2440 				 int ret)
2441 {
2442 	char names[sizeof(seccomp_actions_avail)];
2443 	char old_names[sizeof(seccomp_actions_avail)];
2444 	const char *new = names;
2445 	const char *old = old_names;
2446 
2447 	if (!audit_enabled)
2448 		return;
2449 
2450 	memset(names, 0, sizeof(names));
2451 	memset(old_names, 0, sizeof(old_names));
2452 
2453 	if (ret)
2454 		new = "?";
2455 	else if (!actions_logged)
2456 		new = "(none)";
2457 	else if (!seccomp_names_from_actions_logged(names, sizeof(names),
2458 						    actions_logged, ","))
2459 		new = "?";
2460 
2461 	if (!old_actions_logged)
2462 		old = "(none)";
2463 	else if (!seccomp_names_from_actions_logged(old_names,
2464 						    sizeof(old_names),
2465 						    old_actions_logged, ","))
2466 		old = "?";
2467 
2468 	return audit_seccomp_actions_logged(new, old, !ret);
2469 }
2470 
seccomp_actions_logged_handler(const struct ctl_table * ro_table,int write,void * buffer,size_t * lenp,loff_t * ppos)2471 static int seccomp_actions_logged_handler(const struct ctl_table *ro_table, int write,
2472 					  void *buffer, size_t *lenp,
2473 					  loff_t *ppos)
2474 {
2475 	int ret;
2476 
2477 	if (write) {
2478 		u32 actions_logged = 0;
2479 		u32 old_actions_logged = seccomp_actions_logged;
2480 
2481 		ret = write_actions_logged(ro_table, buffer, lenp, ppos,
2482 					   &actions_logged);
2483 		audit_actions_logged(actions_logged, old_actions_logged, ret);
2484 	} else
2485 		ret = read_actions_logged(ro_table, buffer, lenp, ppos);
2486 
2487 	return ret;
2488 }
2489 
2490 static const struct ctl_table seccomp_sysctl_table[] = {
2491 	{
2492 		.procname	= "actions_avail",
2493 		.data		= (void *) &seccomp_actions_avail,
2494 		.maxlen		= sizeof(seccomp_actions_avail),
2495 		.mode		= 0444,
2496 		.proc_handler	= proc_dostring,
2497 	},
2498 	{
2499 		.procname	= "actions_logged",
2500 		.mode		= 0644,
2501 		.proc_handler	= seccomp_actions_logged_handler,
2502 	},
2503 };
2504 
seccomp_sysctl_init(void)2505 static int __init seccomp_sysctl_init(void)
2506 {
2507 	register_sysctl_init("kernel/seccomp", seccomp_sysctl_table);
2508 	return 0;
2509 }
2510 
device_initcall(seccomp_sysctl_init)2511 device_initcall(seccomp_sysctl_init)
2512 
2513 #endif /* CONFIG_SYSCTL */
2514 
2515 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
2516 /* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */
2517 static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name,
2518 					const void *bitmap, size_t bitmap_size)
2519 {
2520 	int nr;
2521 
2522 	for (nr = 0; nr < bitmap_size; nr++) {
2523 		bool cached = test_bit(nr, bitmap);
2524 		char *status = cached ? "ALLOW" : "FILTER";
2525 
2526 		seq_printf(m, "%s %d %s\n", name, nr, status);
2527 	}
2528 }
2529 
proc_pid_seccomp_cache(struct seq_file * m,struct pid_namespace * ns,struct pid * pid,struct task_struct * task)2530 int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns,
2531 			   struct pid *pid, struct task_struct *task)
2532 {
2533 	struct seccomp_filter *f;
2534 	unsigned long flags;
2535 
2536 	/*
2537 	 * We don't want some sandboxed process to know what their seccomp
2538 	 * filters consist of.
2539 	 */
2540 	if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
2541 		return -EACCES;
2542 
2543 	if (!lock_task_sighand(task, &flags))
2544 		return -ESRCH;
2545 
2546 	f = READ_ONCE(task->seccomp.filter);
2547 	if (!f) {
2548 		unlock_task_sighand(task, &flags);
2549 		return 0;
2550 	}
2551 
2552 	/* prevent filter from being freed while we are printing it */
2553 	__get_seccomp_filter(f);
2554 	unlock_task_sighand(task, &flags);
2555 
2556 	proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME,
2557 				    f->cache.allow_native,
2558 				    SECCOMP_ARCH_NATIVE_NR);
2559 
2560 #ifdef SECCOMP_ARCH_COMPAT
2561 	proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME,
2562 				    f->cache.allow_compat,
2563 				    SECCOMP_ARCH_COMPAT_NR);
2564 #endif /* SECCOMP_ARCH_COMPAT */
2565 
2566 	__put_seccomp_filter(f);
2567 	return 0;
2568 }
2569 #endif /* CONFIG_SECCOMP_CACHE_DEBUG */
2570