1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/fanotify.h>
3 #include <linux/fcntl.h>
4 #include <linux/file.h>
5 #include <linux/fs.h>
6 #include <linux/anon_inodes.h>
7 #include <linux/fsnotify_backend.h>
8 #include <linux/init.h>
9 #include <linux/mount.h>
10 #include <linux/namei.h>
11 #include <linux/poll.h>
12 #include <linux/security.h>
13 #include <linux/syscalls.h>
14 #include <linux/slab.h>
15 #include <linux/types.h>
16 #include <linux/uaccess.h>
17 #include <linux/compat.h>
18 #include <linux/sched/signal.h>
19 #include <linux/memcontrol.h>
20 #include <linux/statfs.h>
21 #include <linux/exportfs.h>
22
23 #include <asm/ioctls.h>
24
25 #include "../fsnotify.h"
26 #include "../fdinfo.h"
27 #include "fanotify.h"
28
29 #define FANOTIFY_DEFAULT_MAX_EVENTS 16384
30 #define FANOTIFY_OLD_DEFAULT_MAX_MARKS 8192
31 #define FANOTIFY_DEFAULT_MAX_GROUPS 128
32 #define FANOTIFY_DEFAULT_FEE_POOL_SIZE 32
33
34 /*
35 * Legacy fanotify marks limits (8192) is per group and we introduced a tunable
36 * limit of marks per user, similar to inotify. Effectively, the legacy limit
37 * of fanotify marks per user is <max marks per group> * <max groups per user>.
38 * This default limit (1M) also happens to match the increased limit of inotify
39 * max_user_watches since v5.10.
40 */
41 #define FANOTIFY_DEFAULT_MAX_USER_MARKS \
42 (FANOTIFY_OLD_DEFAULT_MAX_MARKS * FANOTIFY_DEFAULT_MAX_GROUPS)
43
44 /*
45 * Most of the memory cost of adding an inode mark is pinning the marked inode.
46 * The size of the filesystem inode struct is not uniform across filesystems,
47 * so double the size of a VFS inode is used as a conservative approximation.
48 */
49 #define INODE_MARK_COST (2 * sizeof(struct inode))
50
51 /* configurable via /proc/sys/fs/fanotify/ */
52 static int fanotify_max_queued_events __read_mostly;
53 static int perm_group_timeout __read_mostly;
54
55 #ifdef CONFIG_SYSCTL
56
57 #include <linux/sysctl.h>
58
59 static long ft_zero = 0;
60 static long ft_int_max = INT_MAX;
61
62 static const struct ctl_table fanotify_table[] = {
63 {
64 .procname = "max_user_groups",
65 .data = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS],
66 .maxlen = sizeof(long),
67 .mode = 0644,
68 .proc_handler = proc_doulongvec_minmax,
69 .extra1 = &ft_zero,
70 .extra2 = &ft_int_max,
71 },
72 {
73 .procname = "max_user_marks",
74 .data = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS],
75 .maxlen = sizeof(long),
76 .mode = 0644,
77 .proc_handler = proc_doulongvec_minmax,
78 .extra1 = &ft_zero,
79 .extra2 = &ft_int_max,
80 },
81 {
82 .procname = "max_queued_events",
83 .data = &fanotify_max_queued_events,
84 .maxlen = sizeof(int),
85 .mode = 0644,
86 .proc_handler = proc_dointvec_minmax,
87 .extra1 = SYSCTL_ZERO
88 },
89 {
90 .procname = "watchdog_timeout",
91 .data = &perm_group_timeout,
92 .maxlen = sizeof(int),
93 .mode = 0644,
94 .proc_handler = proc_dointvec_minmax,
95 .extra1 = SYSCTL_ZERO,
96 },
97 };
98
fanotify_sysctls_init(void)99 static void __init fanotify_sysctls_init(void)
100 {
101 register_sysctl("fs/fanotify", fanotify_table);
102 }
103 #else
104 #define fanotify_sysctls_init() do { } while (0)
105 #endif /* CONFIG_SYSCTL */
106
107 static LIST_HEAD(perm_group_list);
108 static DEFINE_SPINLOCK(perm_group_lock);
109 static void perm_group_watchdog(struct work_struct *work);
110 static DECLARE_DELAYED_WORK(perm_group_work, perm_group_watchdog);
111
perm_group_watchdog_schedule(void)112 static void perm_group_watchdog_schedule(void)
113 {
114 schedule_delayed_work(&perm_group_work, secs_to_jiffies(perm_group_timeout));
115 }
116
perm_group_watchdog(struct work_struct * work)117 static void perm_group_watchdog(struct work_struct *work)
118 {
119 struct fsnotify_group *group;
120 struct fanotify_perm_event *event;
121 struct task_struct *task;
122 pid_t failed_pid = 0;
123
124 guard(spinlock)(&perm_group_lock);
125 if (list_empty(&perm_group_list))
126 return;
127
128 list_for_each_entry(group, &perm_group_list,
129 fanotify_data.perm_grp_list) {
130 /*
131 * Ok to test without lock, racing with an addition is
132 * fine, will deal with it next round
133 */
134 if (list_empty(&group->fanotify_data.access_list))
135 continue;
136
137 spin_lock(&group->notification_lock);
138 list_for_each_entry(event, &group->fanotify_data.access_list,
139 fae.fse.list) {
140 if (likely(event->watchdog_cnt == 0)) {
141 event->watchdog_cnt = 1;
142 } else if (event->watchdog_cnt == 1) {
143 /* Report on event only once */
144 event->watchdog_cnt = 2;
145
146 /* Do not report same pid repeatedly */
147 if (event->recv_pid == failed_pid)
148 continue;
149
150 failed_pid = event->recv_pid;
151 rcu_read_lock();
152 task = find_task_by_pid_ns(event->recv_pid,
153 &init_pid_ns);
154 pr_warn_ratelimited(
155 "PID %u (%s) failed to respond to fanotify queue for more than %d seconds\n",
156 event->recv_pid,
157 task ? task->comm : NULL,
158 perm_group_timeout);
159 rcu_read_unlock();
160 }
161 }
162 spin_unlock(&group->notification_lock);
163 }
164 perm_group_watchdog_schedule();
165 }
166
fanotify_perm_watchdog_group_remove(struct fsnotify_group * group)167 static void fanotify_perm_watchdog_group_remove(struct fsnotify_group *group)
168 {
169 if (!list_empty(&group->fanotify_data.perm_grp_list)) {
170 /* Perm event watchdog can no longer scan this group. */
171 spin_lock(&perm_group_lock);
172 list_del_init(&group->fanotify_data.perm_grp_list);
173 spin_unlock(&perm_group_lock);
174 }
175 }
176
fanotify_perm_watchdog_group_add(struct fsnotify_group * group)177 static void fanotify_perm_watchdog_group_add(struct fsnotify_group *group)
178 {
179 if (!perm_group_timeout)
180 return;
181
182 spin_lock(&perm_group_lock);
183 if (list_empty(&group->fanotify_data.perm_grp_list)) {
184 /* Add to perm_group_list for monitoring by watchdog. */
185 if (list_empty(&perm_group_list))
186 perm_group_watchdog_schedule();
187 list_add_tail(&group->fanotify_data.perm_grp_list, &perm_group_list);
188 }
189 spin_unlock(&perm_group_lock);
190 }
191
192 /*
193 * All flags that may be specified in parameter event_f_flags of fanotify_init.
194 *
195 * Internal and external open flags are stored together in field f_flags of
196 * struct file. Only external open flags shall be allowed in event_f_flags.
197 * Internal flags like FMODE_EXEC shall be excluded.
198 */
199 #define FANOTIFY_INIT_ALL_EVENT_F_BITS ( \
200 O_ACCMODE | O_APPEND | O_NONBLOCK | \
201 __O_SYNC | O_DSYNC | O_CLOEXEC | \
202 O_LARGEFILE | O_NOATIME )
203
204 extern const struct fsnotify_ops fanotify_fsnotify_ops;
205
206 struct kmem_cache *fanotify_mark_cache __ro_after_init;
207 struct kmem_cache *fanotify_fid_event_cachep __ro_after_init;
208 struct kmem_cache *fanotify_path_event_cachep __ro_after_init;
209 struct kmem_cache *fanotify_perm_event_cachep __ro_after_init;
210 struct kmem_cache *fanotify_mnt_event_cachep __ro_after_init;
211
212 #define FANOTIFY_EVENT_ALIGN 4
213 #define FANOTIFY_FID_INFO_HDR_LEN \
214 (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
215 #define FANOTIFY_PIDFD_INFO_LEN \
216 sizeof(struct fanotify_event_info_pidfd)
217 #define FANOTIFY_ERROR_INFO_LEN \
218 (sizeof(struct fanotify_event_info_error))
219 #define FANOTIFY_RANGE_INFO_LEN \
220 (sizeof(struct fanotify_event_info_range))
221 #define FANOTIFY_MNT_INFO_LEN \
222 (sizeof(struct fanotify_event_info_mnt))
223
fanotify_fid_info_len(int fh_len,int name_len)224 static int fanotify_fid_info_len(int fh_len, int name_len)
225 {
226 int info_len = fh_len;
227
228 if (name_len)
229 info_len += name_len + 1;
230
231 return roundup(FANOTIFY_FID_INFO_HDR_LEN + info_len,
232 FANOTIFY_EVENT_ALIGN);
233 }
234
235 /* FAN_RENAME may have one or two dir+name info records */
fanotify_dir_name_info_len(struct fanotify_event * event)236 static int fanotify_dir_name_info_len(struct fanotify_event *event)
237 {
238 struct fanotify_info *info = fanotify_event_info(event);
239 int dir_fh_len = fanotify_event_dir_fh_len(event);
240 int dir2_fh_len = fanotify_event_dir2_fh_len(event);
241 int info_len = 0;
242
243 if (dir_fh_len)
244 info_len += fanotify_fid_info_len(dir_fh_len,
245 info->name_len);
246 if (dir2_fh_len)
247 info_len += fanotify_fid_info_len(dir2_fh_len,
248 info->name2_len);
249
250 return info_len;
251 }
252
fanotify_event_len(unsigned int info_mode,struct fanotify_event * event)253 static size_t fanotify_event_len(unsigned int info_mode,
254 struct fanotify_event *event)
255 {
256 size_t event_len = FAN_EVENT_METADATA_LEN;
257 int fh_len;
258 int dot_len = 0;
259
260 if (fanotify_is_error_event(event->mask))
261 event_len += FANOTIFY_ERROR_INFO_LEN;
262
263 if (fanotify_event_has_any_dir_fh(event)) {
264 event_len += fanotify_dir_name_info_len(event);
265 } else if ((info_mode & FAN_REPORT_NAME) &&
266 (event->mask & FAN_ONDIR)) {
267 /*
268 * With group flag FAN_REPORT_NAME, if name was not recorded in
269 * event on a directory, we will report the name ".".
270 */
271 dot_len = 1;
272 }
273
274 if (fanotify_event_has_object_fh(event)) {
275 fh_len = fanotify_event_object_fh_len(event);
276 event_len += fanotify_fid_info_len(fh_len, dot_len);
277 }
278 if (fanotify_is_mnt_event(event->mask))
279 event_len += FANOTIFY_MNT_INFO_LEN;
280
281 if (info_mode & FAN_REPORT_PIDFD)
282 event_len += FANOTIFY_PIDFD_INFO_LEN;
283
284 if (fanotify_event_has_access_range(event))
285 event_len += FANOTIFY_RANGE_INFO_LEN;
286
287 return event_len;
288 }
289
290 /*
291 * Remove an hashed event from merge hash table.
292 */
fanotify_unhash_event(struct fsnotify_group * group,struct fanotify_event * event)293 static void fanotify_unhash_event(struct fsnotify_group *group,
294 struct fanotify_event *event)
295 {
296 assert_spin_locked(&group->notification_lock);
297
298 pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
299 group, event, fanotify_event_hash_bucket(group, event));
300
301 if (WARN_ON_ONCE(hlist_unhashed(&event->merge_list)))
302 return;
303
304 hlist_del_init(&event->merge_list);
305 }
306
307 /*
308 * Get an fanotify notification event if one exists and is small
309 * enough to fit in "count". Return an error pointer if the count
310 * is not large enough. When permission event is dequeued, its state is
311 * updated accordingly.
312 */
get_one_event(struct fsnotify_group * group,size_t count)313 static struct fanotify_event *get_one_event(struct fsnotify_group *group,
314 size_t count)
315 {
316 size_t event_size;
317 struct fanotify_event *event = NULL;
318 struct fsnotify_event *fsn_event;
319 unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
320
321 pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
322
323 spin_lock(&group->notification_lock);
324 fsn_event = fsnotify_peek_first_event(group);
325 if (!fsn_event)
326 goto out;
327
328 event = FANOTIFY_E(fsn_event);
329 event_size = fanotify_event_len(info_mode, event);
330
331 if (event_size > count) {
332 event = ERR_PTR(-EINVAL);
333 goto out;
334 }
335
336 /*
337 * Held the notification_lock the whole time, so this is the
338 * same event we peeked above.
339 */
340 fsnotify_remove_first_event(group);
341 if (fanotify_is_perm_event(event->mask))
342 FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
343 if (fanotify_is_hashed_event(event->mask))
344 fanotify_unhash_event(group, event);
345 out:
346 spin_unlock(&group->notification_lock);
347 return event;
348 }
349
create_fd(struct fsnotify_group * group,const struct path * path,struct file ** file)350 static int create_fd(struct fsnotify_group *group, const struct path *path,
351 struct file **file)
352 {
353 int client_fd;
354 struct file *new_file;
355
356 client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
357 if (client_fd < 0)
358 return client_fd;
359
360 /*
361 * We provide an fd for the userspace program, so it could access the
362 * file without generating fanotify events itself.
363 */
364 new_file = dentry_open_nonotify(path, group->fanotify_data.f_flags,
365 current_cred());
366 if (IS_ERR(new_file)) {
367 put_unused_fd(client_fd);
368 client_fd = PTR_ERR(new_file);
369 } else {
370 *file = new_file;
371 }
372
373 return client_fd;
374 }
375
process_access_response_info(const char __user * info,size_t info_len,struct fanotify_response_info_audit_rule * friar)376 static int process_access_response_info(const char __user *info,
377 size_t info_len,
378 struct fanotify_response_info_audit_rule *friar)
379 {
380 if (info_len != sizeof(*friar))
381 return -EINVAL;
382
383 if (copy_from_user(friar, info, sizeof(*friar)))
384 return -EFAULT;
385
386 if (friar->hdr.type != FAN_RESPONSE_INFO_AUDIT_RULE)
387 return -EINVAL;
388 if (friar->hdr.pad != 0)
389 return -EINVAL;
390 if (friar->hdr.len != sizeof(*friar))
391 return -EINVAL;
392
393 return info_len;
394 }
395
396 /*
397 * Finish processing of permission event by setting it to ANSWERED state and
398 * drop group->notification_lock.
399 */
finish_permission_event(struct fsnotify_group * group,struct fanotify_perm_event * event,u32 response,struct fanotify_response_info_audit_rule * friar)400 static void finish_permission_event(struct fsnotify_group *group,
401 struct fanotify_perm_event *event, u32 response,
402 struct fanotify_response_info_audit_rule *friar)
403 __releases(&group->notification_lock)
404 {
405 bool destroy = false;
406
407 assert_spin_locked(&group->notification_lock);
408 event->response = response & ~FAN_INFO;
409 if (response & FAN_INFO)
410 memcpy(&event->audit_rule, friar, sizeof(*friar));
411
412 if (event->state == FAN_EVENT_CANCELED)
413 destroy = true;
414 else
415 event->state = FAN_EVENT_ANSWERED;
416 spin_unlock(&group->notification_lock);
417 if (destroy)
418 fsnotify_destroy_event(group, &event->fae.fse);
419 }
420
process_access_response(struct fsnotify_group * group,struct fanotify_response * response_struct,const char __user * info,size_t info_len)421 static int process_access_response(struct fsnotify_group *group,
422 struct fanotify_response *response_struct,
423 const char __user *info,
424 size_t info_len)
425 {
426 struct fanotify_perm_event *event;
427 int fd = response_struct->fd;
428 u32 response = response_struct->response;
429 int errno = fanotify_get_response_errno(response);
430 int ret = info_len;
431 struct fanotify_response_info_audit_rule friar;
432
433 pr_debug("%s: group=%p fd=%d response=%x errno=%d buf=%p size=%zu\n",
434 __func__, group, fd, response, errno, info, info_len);
435 /*
436 * make sure the response is valid, if invalid we do nothing and either
437 * userspace can send a valid response or we will clean it up after the
438 * timeout
439 */
440 if (response & ~FANOTIFY_RESPONSE_VALID_MASK)
441 return -EINVAL;
442
443 switch (response & FANOTIFY_RESPONSE_ACCESS) {
444 case FAN_ALLOW:
445 if (errno)
446 return -EINVAL;
447 break;
448 case FAN_DENY:
449 /* Custom errno is supported only for pre-content groups */
450 if (errno && group->priority != FSNOTIFY_PRIO_PRE_CONTENT)
451 return -EINVAL;
452
453 /*
454 * Limit errno to values expected on open(2)/read(2)/write(2)
455 * of regular files.
456 */
457 switch (errno) {
458 case 0:
459 case EIO:
460 case EPERM:
461 case EBUSY:
462 case ETXTBSY:
463 case EAGAIN:
464 case ENOSPC:
465 case EDQUOT:
466 break;
467 default:
468 return -EINVAL;
469 }
470 break;
471 default:
472 return -EINVAL;
473 }
474
475 if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
476 return -EINVAL;
477
478 if (response & FAN_INFO) {
479 ret = process_access_response_info(info, info_len, &friar);
480 if (ret < 0)
481 return ret;
482 if (fd == FAN_NOFD)
483 return ret;
484 } else {
485 ret = 0;
486 }
487
488 if (fd < 0)
489 return -EINVAL;
490
491 spin_lock(&group->notification_lock);
492 list_for_each_entry(event, &group->fanotify_data.access_list,
493 fae.fse.list) {
494 if (event->fd != fd)
495 continue;
496
497 list_del_init(&event->fae.fse.list);
498 finish_permission_event(group, event, response, &friar);
499 wake_up(&group->fanotify_data.access_waitq);
500 return ret;
501 }
502 spin_unlock(&group->notification_lock);
503
504 return -ENOENT;
505 }
506
copy_mnt_info_to_user(struct fanotify_event * event,char __user * buf,int count)507 static size_t copy_mnt_info_to_user(struct fanotify_event *event,
508 char __user *buf, int count)
509 {
510 struct fanotify_event_info_mnt info = { };
511
512 info.hdr.info_type = FAN_EVENT_INFO_TYPE_MNT;
513 info.hdr.len = FANOTIFY_MNT_INFO_LEN;
514
515 if (WARN_ON(count < info.hdr.len))
516 return -EFAULT;
517
518 info.mnt_id = FANOTIFY_ME(event)->mnt_id;
519
520 if (copy_to_user(buf, &info, sizeof(info)))
521 return -EFAULT;
522
523 return info.hdr.len;
524 }
525
copy_error_info_to_user(struct fanotify_event * event,char __user * buf,int count)526 static size_t copy_error_info_to_user(struct fanotify_event *event,
527 char __user *buf, int count)
528 {
529 struct fanotify_event_info_error info = { };
530 struct fanotify_error_event *fee = FANOTIFY_EE(event);
531
532 info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
533 info.hdr.len = FANOTIFY_ERROR_INFO_LEN;
534
535 if (WARN_ON(count < info.hdr.len))
536 return -EFAULT;
537
538 info.error = fee->error;
539 info.error_count = fee->err_count;
540
541 if (copy_to_user(buf, &info, sizeof(info)))
542 return -EFAULT;
543
544 return info.hdr.len;
545 }
546
copy_fid_info_to_user(__kernel_fsid_t * fsid,struct fanotify_fh * fh,int info_type,const char * name,size_t name_len,char __user * buf,size_t count)547 static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
548 int info_type, const char *name,
549 size_t name_len,
550 char __user *buf, size_t count)
551 {
552 struct fanotify_event_info_fid info = { };
553 struct file_handle handle = { };
554 unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf;
555 size_t fh_len = fh ? fh->len : 0;
556 size_t info_len = fanotify_fid_info_len(fh_len, name_len);
557 size_t len = info_len;
558
559 pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
560 __func__, fh_len, name_len, info_len, count);
561
562 if (WARN_ON_ONCE(len < sizeof(info) || len > count))
563 return -EFAULT;
564
565 /*
566 * Copy event info fid header followed by variable sized file handle
567 * and optionally followed by variable sized filename.
568 */
569 switch (info_type) {
570 case FAN_EVENT_INFO_TYPE_FID:
571 case FAN_EVENT_INFO_TYPE_DFID:
572 if (WARN_ON_ONCE(name_len))
573 return -EFAULT;
574 break;
575 case FAN_EVENT_INFO_TYPE_DFID_NAME:
576 case FAN_EVENT_INFO_TYPE_OLD_DFID_NAME:
577 case FAN_EVENT_INFO_TYPE_NEW_DFID_NAME:
578 if (WARN_ON_ONCE(!name || !name_len))
579 return -EFAULT;
580 break;
581 default:
582 return -EFAULT;
583 }
584
585 info.hdr.info_type = info_type;
586 info.hdr.len = len;
587 info.fsid = *fsid;
588 if (copy_to_user(buf, &info, sizeof(info)))
589 return -EFAULT;
590
591 buf += sizeof(info);
592 len -= sizeof(info);
593 if (WARN_ON_ONCE(len < sizeof(handle)))
594 return -EFAULT;
595
596 handle.handle_type = fh->type;
597 handle.handle_bytes = fh_len;
598
599 /* Mangle handle_type for bad file_handle */
600 if (!fh_len)
601 handle.handle_type = FILEID_INVALID;
602
603 if (copy_to_user(buf, &handle, sizeof(handle)))
604 return -EFAULT;
605
606 buf += sizeof(handle);
607 len -= sizeof(handle);
608 if (WARN_ON_ONCE(len < fh_len))
609 return -EFAULT;
610
611 /*
612 * For an inline fh and inline file name, copy through stack to exclude
613 * the copy from usercopy hardening protections.
614 */
615 fh_buf = fanotify_fh_buf(fh);
616 if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
617 memcpy(bounce, fh_buf, fh_len);
618 fh_buf = bounce;
619 }
620 if (copy_to_user(buf, fh_buf, fh_len))
621 return -EFAULT;
622
623 buf += fh_len;
624 len -= fh_len;
625
626 if (name_len) {
627 /* Copy the filename with terminating null */
628 name_len++;
629 if (WARN_ON_ONCE(len < name_len))
630 return -EFAULT;
631
632 if (copy_to_user(buf, name, name_len))
633 return -EFAULT;
634
635 buf += name_len;
636 len -= name_len;
637 }
638
639 /* Pad with 0's */
640 WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
641 if (len > 0 && clear_user(buf, len))
642 return -EFAULT;
643
644 return info_len;
645 }
646
copy_pidfd_info_to_user(int pidfd,char __user * buf,size_t count)647 static int copy_pidfd_info_to_user(int pidfd,
648 char __user *buf,
649 size_t count)
650 {
651 struct fanotify_event_info_pidfd info = { };
652 size_t info_len = FANOTIFY_PIDFD_INFO_LEN;
653
654 if (WARN_ON_ONCE(info_len > count))
655 return -EFAULT;
656
657 info.hdr.info_type = FAN_EVENT_INFO_TYPE_PIDFD;
658 info.hdr.len = info_len;
659 info.pidfd = pidfd;
660
661 if (copy_to_user(buf, &info, info_len))
662 return -EFAULT;
663
664 return info_len;
665 }
666
copy_range_info_to_user(struct fanotify_event * event,char __user * buf,int count)667 static size_t copy_range_info_to_user(struct fanotify_event *event,
668 char __user *buf, int count)
669 {
670 struct fanotify_perm_event *pevent = FANOTIFY_PERM(event);
671 struct fanotify_event_info_range info = { };
672 size_t info_len = FANOTIFY_RANGE_INFO_LEN;
673
674 if (WARN_ON_ONCE(info_len > count))
675 return -EFAULT;
676
677 if (WARN_ON_ONCE(!pevent->ppos))
678 return -EINVAL;
679
680 info.hdr.info_type = FAN_EVENT_INFO_TYPE_RANGE;
681 info.hdr.len = info_len;
682 info.offset = *(pevent->ppos);
683 info.count = pevent->count;
684
685 if (copy_to_user(buf, &info, info_len))
686 return -EFAULT;
687
688 return info_len;
689 }
690
copy_info_records_to_user(struct fanotify_event * event,struct fanotify_info * info,unsigned int info_mode,int pidfd,char __user * buf,size_t count)691 static int copy_info_records_to_user(struct fanotify_event *event,
692 struct fanotify_info *info,
693 unsigned int info_mode, int pidfd,
694 char __user *buf, size_t count)
695 {
696 int ret, total_bytes = 0, info_type = 0;
697 unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;
698 unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
699
700 /*
701 * Event info records order is as follows:
702 * 1. dir fid + name
703 * 2. (optional) new dir fid + new name
704 * 3. (optional) child fid
705 */
706 if (fanotify_event_has_dir_fh(event)) {
707 info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
708 FAN_EVENT_INFO_TYPE_DFID;
709
710 /* FAN_RENAME uses special info types */
711 if (event->mask & FAN_RENAME)
712 info_type = FAN_EVENT_INFO_TYPE_OLD_DFID_NAME;
713
714 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
715 fanotify_info_dir_fh(info),
716 info_type,
717 fanotify_info_name(info),
718 info->name_len, buf, count);
719 if (ret < 0)
720 return ret;
721
722 buf += ret;
723 count -= ret;
724 total_bytes += ret;
725 }
726
727 /* New dir fid+name may be reported in addition to old dir fid+name */
728 if (fanotify_event_has_dir2_fh(event)) {
729 info_type = FAN_EVENT_INFO_TYPE_NEW_DFID_NAME;
730 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
731 fanotify_info_dir2_fh(info),
732 info_type,
733 fanotify_info_name2(info),
734 info->name2_len, buf, count);
735 if (ret < 0)
736 return ret;
737
738 buf += ret;
739 count -= ret;
740 total_bytes += ret;
741 }
742
743 if (fanotify_event_has_object_fh(event)) {
744 const char *dot = NULL;
745 int dot_len = 0;
746
747 if (fid_mode == FAN_REPORT_FID || info_type) {
748 /*
749 * With only group flag FAN_REPORT_FID only type FID is
750 * reported. Second info record type is always FID.
751 */
752 info_type = FAN_EVENT_INFO_TYPE_FID;
753 } else if ((fid_mode & FAN_REPORT_NAME) &&
754 (event->mask & FAN_ONDIR)) {
755 /*
756 * With group flag FAN_REPORT_NAME, if name was not
757 * recorded in an event on a directory, report the name
758 * "." with info type DFID_NAME.
759 */
760 info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
761 dot = ".";
762 dot_len = 1;
763 } else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
764 (event->mask & FAN_ONDIR)) {
765 /*
766 * With group flag FAN_REPORT_DIR_FID, a single info
767 * record has type DFID for directory entry modification
768 * event and for event on a directory.
769 */
770 info_type = FAN_EVENT_INFO_TYPE_DFID;
771 } else {
772 /*
773 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,
774 * a single info record has type FID for event on a
775 * non-directory, when there is no directory to report.
776 * For example, on FAN_DELETE_SELF event.
777 */
778 info_type = FAN_EVENT_INFO_TYPE_FID;
779 }
780
781 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
782 fanotify_event_object_fh(event),
783 info_type, dot, dot_len,
784 buf, count);
785 if (ret < 0)
786 return ret;
787
788 buf += ret;
789 count -= ret;
790 total_bytes += ret;
791 }
792
793 if (pidfd_mode) {
794 ret = copy_pidfd_info_to_user(pidfd, buf, count);
795 if (ret < 0)
796 return ret;
797
798 buf += ret;
799 count -= ret;
800 total_bytes += ret;
801 }
802
803 if (fanotify_is_error_event(event->mask)) {
804 ret = copy_error_info_to_user(event, buf, count);
805 if (ret < 0)
806 return ret;
807 buf += ret;
808 count -= ret;
809 total_bytes += ret;
810 }
811
812 if (fanotify_event_has_access_range(event)) {
813 ret = copy_range_info_to_user(event, buf, count);
814 if (ret < 0)
815 return ret;
816 buf += ret;
817 count -= ret;
818 total_bytes += ret;
819 }
820
821 if (fanotify_is_mnt_event(event->mask)) {
822 ret = copy_mnt_info_to_user(event, buf, count);
823 if (ret < 0)
824 return ret;
825 buf += ret;
826 count -= ret;
827 total_bytes += ret;
828 }
829
830 return total_bytes;
831 }
832
copy_event_to_user(struct fsnotify_group * group,struct fanotify_event * event,char __user * buf,size_t count)833 static ssize_t copy_event_to_user(struct fsnotify_group *group,
834 struct fanotify_event *event,
835 char __user *buf, size_t count)
836 {
837 struct fanotify_event_metadata metadata;
838 const struct path *path = fanotify_event_path(event);
839 struct fanotify_info *info = fanotify_event_info(event);
840 unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
841 unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
842 struct file *f = NULL, *pidfd_file = NULL;
843 int ret, pidfd = -ESRCH, fd = -EBADF;
844
845 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
846
847 metadata.event_len = fanotify_event_len(info_mode, event);
848 metadata.metadata_len = FAN_EVENT_METADATA_LEN;
849 metadata.vers = FANOTIFY_METADATA_VERSION;
850 metadata.reserved = 0;
851 metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
852 metadata.pid = pid_vnr(event->pid);
853 /*
854 * For an unprivileged listener, event->pid can be used to identify the
855 * events generated by the listener process itself, without disclosing
856 * the pids of other processes.
857 */
858 if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
859 task_tgid(current) != event->pid)
860 metadata.pid = 0;
861
862 /*
863 * For now, fid mode is required for an unprivileged listener and
864 * fid mode does not report fd in events. Keep this check anyway
865 * for safety in case fid mode requirement is relaxed in the future
866 * to allow unprivileged listener to get events with no fd and no fid.
867 */
868 if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
869 path && path->mnt && path->dentry) {
870 fd = create_fd(group, path, &f);
871 /*
872 * Opening an fd from dentry can fail for several reasons.
873 * For example, when tasks are gone and we try to open their
874 * /proc files or we try to open a WRONLY file like in sysfs
875 * or when trying to open a file that was deleted on the
876 * remote network server.
877 *
878 * For a group with FAN_REPORT_FD_ERROR, we will send the
879 * event with the error instead of the open fd, otherwise
880 * Userspace may not get the error at all.
881 * In any case, userspace will not know which file failed to
882 * open, so add a debug print for further investigation.
883 */
884 if (fd < 0) {
885 pr_debug("fanotify: create_fd(%pd2) failed err=%d\n",
886 path->dentry, fd);
887 if (!FAN_GROUP_FLAG(group, FAN_REPORT_FD_ERROR)) {
888 /*
889 * Historically, we've handled EOPENSTALE in a
890 * special way and silently dropped such
891 * events. Now we have to keep it to maintain
892 * backward compatibility...
893 */
894 if (fd == -EOPENSTALE)
895 fd = 0;
896 return fd;
897 }
898 }
899 }
900 if (FAN_GROUP_FLAG(group, FAN_REPORT_FD_ERROR))
901 metadata.fd = fd;
902 else
903 metadata.fd = fd >= 0 ? fd : FAN_NOFD;
904
905 if (pidfd_mode) {
906 /*
907 * Complain if the FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
908 * exclusion is ever lifted. At the time of incoporating pidfd
909 * support within fanotify, the pidfd API only supported the
910 * creation of pidfds for thread-group leaders.
911 */
912 WARN_ON_ONCE(FAN_GROUP_FLAG(group, FAN_REPORT_TID));
913
914 /*
915 * The PIDTYPE_TGID check for an event->pid is performed
916 * preemptively in an attempt to catch out cases where the event
917 * listener reads events after the event generating process has
918 * already terminated. Depending on flag FAN_REPORT_FD_ERROR,
919 * report either -ESRCH or FAN_NOPIDFD to the event listener in
920 * those cases with all other pidfd creation errors reported as
921 * the error code itself or as FAN_EPIDFD.
922 */
923 if (metadata.pid && pid_has_task(event->pid, PIDTYPE_TGID))
924 pidfd = pidfd_prepare(event->pid, 0, &pidfd_file);
925
926 if (!FAN_GROUP_FLAG(group, FAN_REPORT_FD_ERROR) && pidfd < 0)
927 pidfd = pidfd == -ESRCH ? FAN_NOPIDFD : FAN_EPIDFD;
928 }
929
930 ret = -EFAULT;
931 /*
932 * Sanity check copy size in case get_one_event() and
933 * event_len sizes ever get out of sync.
934 */
935 if (WARN_ON_ONCE(metadata.event_len > count))
936 goto out_close_fd;
937
938 if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
939 goto out_close_fd;
940
941 buf += FAN_EVENT_METADATA_LEN;
942 count -= FAN_EVENT_METADATA_LEN;
943
944 ret = copy_info_records_to_user(event, info, info_mode, pidfd,
945 buf, count);
946 if (ret < 0)
947 goto out_close_fd;
948
949 if (f)
950 fd_install(fd, f);
951
952 if (pidfd_file)
953 fd_install(pidfd, pidfd_file);
954
955 if (fanotify_is_perm_event(event->mask))
956 FANOTIFY_PERM(event)->fd = fd;
957
958 return metadata.event_len;
959
960 out_close_fd:
961 if (f) {
962 put_unused_fd(fd);
963 fput(f);
964 }
965
966 if (pidfd_file) {
967 put_unused_fd(pidfd);
968 fput(pidfd_file);
969 }
970
971 return ret;
972 }
973
974 /* intofiy userspace file descriptor functions */
fanotify_poll(struct file * file,poll_table * wait)975 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
976 {
977 struct fsnotify_group *group = file->private_data;
978 __poll_t ret = 0;
979
980 poll_wait(file, &group->notification_waitq, wait);
981 spin_lock(&group->notification_lock);
982 if (!fsnotify_notify_queue_is_empty(group))
983 ret = EPOLLIN | EPOLLRDNORM;
984 spin_unlock(&group->notification_lock);
985
986 return ret;
987 }
988
fanotify_read(struct file * file,char __user * buf,size_t count,loff_t * pos)989 static ssize_t fanotify_read(struct file *file, char __user *buf,
990 size_t count, loff_t *pos)
991 {
992 struct fsnotify_group *group;
993 struct fanotify_event *event;
994 char __user *start;
995 int ret;
996 DEFINE_WAIT_FUNC(wait, woken_wake_function);
997
998 start = buf;
999 group = file->private_data;
1000
1001 pr_debug("%s: group=%p\n", __func__, group);
1002
1003 add_wait_queue(&group->notification_waitq, &wait);
1004 while (1) {
1005 /*
1006 * User can supply arbitrarily large buffer. Avoid softlockups
1007 * in case there are lots of available events.
1008 */
1009 cond_resched();
1010 event = get_one_event(group, count);
1011 if (IS_ERR(event)) {
1012 ret = PTR_ERR(event);
1013 break;
1014 }
1015
1016 if (!event) {
1017 ret = -EAGAIN;
1018 if (file->f_flags & O_NONBLOCK)
1019 break;
1020
1021 ret = -ERESTARTSYS;
1022 if (signal_pending(current))
1023 break;
1024
1025 if (start != buf)
1026 break;
1027
1028 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
1029 continue;
1030 }
1031
1032 ret = copy_event_to_user(group, event, buf, count);
1033
1034 /*
1035 * Permission events get queued to wait for response. Other
1036 * events can be destroyed now.
1037 */
1038 if (!fanotify_is_perm_event(event->mask)) {
1039 fsnotify_destroy_event(group, &event->fse);
1040 } else {
1041 if (ret <= 0 || FANOTIFY_PERM(event)->fd < 0) {
1042 spin_lock(&group->notification_lock);
1043 finish_permission_event(group,
1044 FANOTIFY_PERM(event), FAN_DENY, NULL);
1045 wake_up(&group->fanotify_data.access_waitq);
1046 } else {
1047 spin_lock(&group->notification_lock);
1048 list_add_tail(&event->fse.list,
1049 &group->fanotify_data.access_list);
1050 FANOTIFY_PERM(event)->recv_pid = current->pid;
1051 spin_unlock(&group->notification_lock);
1052 }
1053 }
1054 if (ret < 0)
1055 break;
1056 buf += ret;
1057 count -= ret;
1058 }
1059 remove_wait_queue(&group->notification_waitq, &wait);
1060
1061 if (start != buf && ret != -EFAULT)
1062 ret = buf - start;
1063 return ret;
1064 }
1065
fanotify_write(struct file * file,const char __user * buf,size_t count,loff_t * pos)1066 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
1067 {
1068 struct fanotify_response response;
1069 struct fsnotify_group *group;
1070 int ret;
1071 const char __user *info_buf = buf + sizeof(struct fanotify_response);
1072 size_t info_len;
1073
1074 if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1075 return -EINVAL;
1076
1077 group = file->private_data;
1078
1079 pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
1080
1081 if (count < sizeof(response))
1082 return -EINVAL;
1083
1084 if (copy_from_user(&response, buf, sizeof(response)))
1085 return -EFAULT;
1086
1087 info_len = count - sizeof(response);
1088
1089 ret = process_access_response(group, &response, info_buf, info_len);
1090 if (ret < 0)
1091 count = ret;
1092 else
1093 count = sizeof(response) + ret;
1094
1095 return count;
1096 }
1097
fanotify_release(struct inode * ignored,struct file * file)1098 static int fanotify_release(struct inode *ignored, struct file *file)
1099 {
1100 struct fsnotify_group *group = file->private_data;
1101 struct fsnotify_event *fsn_event;
1102
1103 /*
1104 * Stop new events from arriving in the notification queue. since
1105 * userspace cannot use fanotify fd anymore, no event can enter or
1106 * leave access_list by now either.
1107 */
1108 fsnotify_group_stop_queueing(group);
1109
1110 fanotify_perm_watchdog_group_remove(group);
1111
1112 /*
1113 * Process all permission events on access_list and notification queue
1114 * and simulate reply from userspace.
1115 */
1116 spin_lock(&group->notification_lock);
1117 while (!list_empty(&group->fanotify_data.access_list)) {
1118 struct fanotify_perm_event *event;
1119
1120 event = list_first_entry(&group->fanotify_data.access_list,
1121 struct fanotify_perm_event, fae.fse.list);
1122 list_del_init(&event->fae.fse.list);
1123 finish_permission_event(group, event, FAN_ALLOW, NULL);
1124 spin_lock(&group->notification_lock);
1125 }
1126
1127 /*
1128 * Destroy all non-permission events. For permission events just
1129 * dequeue them and set the response. They will be freed once the
1130 * response is consumed and fanotify_get_response() returns.
1131 */
1132 while ((fsn_event = fsnotify_remove_first_event(group))) {
1133 struct fanotify_event *event = FANOTIFY_E(fsn_event);
1134
1135 if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
1136 spin_unlock(&group->notification_lock);
1137 fsnotify_destroy_event(group, fsn_event);
1138 } else {
1139 finish_permission_event(group, FANOTIFY_PERM(event),
1140 FAN_ALLOW, NULL);
1141 }
1142 spin_lock(&group->notification_lock);
1143 }
1144 spin_unlock(&group->notification_lock);
1145
1146 /* Response for all permission events it set, wakeup waiters */
1147 wake_up(&group->fanotify_data.access_waitq);
1148
1149 /* matches the fanotify_init->fsnotify_alloc_group */
1150 fsnotify_destroy_group(group);
1151
1152 return 0;
1153 }
1154
fanotify_ioctl(struct file * file,unsigned int cmd,unsigned long arg)1155 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
1156 {
1157 struct fsnotify_group *group;
1158 struct fsnotify_event *fsn_event;
1159 void __user *p;
1160 int ret = -ENOTTY;
1161 size_t send_len = 0;
1162
1163 group = file->private_data;
1164
1165 p = (void __user *) arg;
1166
1167 switch (cmd) {
1168 case FIONREAD:
1169 spin_lock(&group->notification_lock);
1170 list_for_each_entry(fsn_event, &group->notification_list, list)
1171 send_len += FAN_EVENT_METADATA_LEN;
1172 spin_unlock(&group->notification_lock);
1173 ret = put_user(send_len, (int __user *) p);
1174 break;
1175 }
1176
1177 return ret;
1178 }
1179
1180 static const struct file_operations fanotify_fops = {
1181 .show_fdinfo = fanotify_show_fdinfo,
1182 .poll = fanotify_poll,
1183 .read = fanotify_read,
1184 .write = fanotify_write,
1185 .fasync = NULL,
1186 .release = fanotify_release,
1187 .unlocked_ioctl = fanotify_ioctl,
1188 .compat_ioctl = compat_ptr_ioctl,
1189 .llseek = noop_llseek,
1190 };
1191
fanotify_find_path(int dfd,const char __user * filename,struct path * path,unsigned int flags,__u64 mask,unsigned int obj_type)1192 static int fanotify_find_path(int dfd, const char __user *filename,
1193 struct path *path, unsigned int flags, __u64 mask,
1194 unsigned int obj_type)
1195 {
1196 int ret;
1197
1198 pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
1199 dfd, filename, flags);
1200
1201 if (filename == NULL) {
1202 CLASS(fd, f)(dfd);
1203
1204 if (fd_empty(f))
1205 return -EBADF;
1206
1207 if ((flags & FAN_MARK_ONLYDIR) &&
1208 !(S_ISDIR(file_inode(fd_file(f))->i_mode)))
1209 return -ENOTDIR;
1210
1211 *path = fd_file(f)->f_path;
1212 path_get(path);
1213 } else {
1214 unsigned int lookup_flags = 0;
1215
1216 if (!(flags & FAN_MARK_DONT_FOLLOW))
1217 lookup_flags |= LOOKUP_FOLLOW;
1218 if (flags & FAN_MARK_ONLYDIR)
1219 lookup_flags |= LOOKUP_DIRECTORY;
1220
1221 ret = user_path_at(dfd, filename, lookup_flags, path);
1222 if (ret)
1223 goto out;
1224 }
1225
1226 /* you can only watch an inode if you have read permissions on it */
1227 ret = path_permission(path, MAY_READ);
1228 if (ret) {
1229 path_put(path);
1230 goto out;
1231 }
1232
1233 ret = security_path_notify(path, mask, obj_type);
1234 if (ret)
1235 path_put(path);
1236
1237 out:
1238 return ret;
1239 }
1240
fanotify_mark_remove_from_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int flags,__u32 umask,int * destroy)1241 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
1242 __u32 mask, unsigned int flags,
1243 __u32 umask, int *destroy)
1244 {
1245 __u32 oldmask, newmask;
1246
1247 /* umask bits cannot be removed by user */
1248 mask &= ~umask;
1249 spin_lock(&fsn_mark->lock);
1250 oldmask = fsnotify_calc_mask(fsn_mark);
1251 if (!(flags & FANOTIFY_MARK_IGNORE_BITS)) {
1252 fsn_mark->mask &= ~mask;
1253 } else {
1254 fsn_mark->ignore_mask &= ~mask;
1255 }
1256 newmask = fsnotify_calc_mask(fsn_mark);
1257 /*
1258 * We need to keep the mark around even if remaining mask cannot
1259 * result in any events (e.g. mask == FAN_ONDIR) to support incremenal
1260 * changes to the mask.
1261 * Destroy mark when only umask bits remain.
1262 */
1263 *destroy = !((fsn_mark->mask | fsn_mark->ignore_mask) & ~umask);
1264 spin_unlock(&fsn_mark->lock);
1265
1266 return oldmask & ~newmask;
1267 }
1268
fanotify_remove_mark(struct fsnotify_group * group,void * obj,unsigned int obj_type,__u32 mask,unsigned int flags,__u32 umask)1269 static int fanotify_remove_mark(struct fsnotify_group *group,
1270 void *obj, unsigned int obj_type, __u32 mask,
1271 unsigned int flags, __u32 umask)
1272 {
1273 struct fsnotify_mark *fsn_mark = NULL;
1274 __u32 removed;
1275 int destroy_mark;
1276
1277 fsnotify_group_lock(group);
1278 fsn_mark = fsnotify_find_mark(obj, obj_type, group);
1279 if (!fsn_mark) {
1280 fsnotify_group_unlock(group);
1281 return -ENOENT;
1282 }
1283
1284 removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
1285 umask, &destroy_mark);
1286 if (removed & fsnotify_conn_mask(fsn_mark->connector))
1287 fsnotify_recalc_mask(fsn_mark->connector);
1288 if (destroy_mark)
1289 fsnotify_detach_mark(fsn_mark);
1290 fsnotify_group_unlock(group);
1291 if (destroy_mark)
1292 fsnotify_free_mark(fsn_mark);
1293
1294 /* matches the fsnotify_find_mark() */
1295 fsnotify_put_mark(fsn_mark);
1296 return 0;
1297 }
1298
fanotify_mark_update_flags(struct fsnotify_mark * fsn_mark,unsigned int fan_flags)1299 static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
1300 unsigned int fan_flags)
1301 {
1302 bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);
1303 unsigned int ignore = fan_flags & FANOTIFY_MARK_IGNORE_BITS;
1304 bool recalc = false;
1305
1306 /*
1307 * When using FAN_MARK_IGNORE for the first time, mark starts using
1308 * independent event flags in ignore mask. After that, trying to
1309 * update the ignore mask with the old FAN_MARK_IGNORED_MASK API
1310 * will result in EEXIST error.
1311 */
1312 if (ignore == FAN_MARK_IGNORE)
1313 fsn_mark->flags |= FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS;
1314
1315 /*
1316 * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to
1317 * the removal of the FS_MODIFY bit in calculated mask if it was set
1318 * because of an ignore mask that is now going to survive FS_MODIFY.
1319 */
1320 if (ignore && (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1321 !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) {
1322 fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
1323 if (!(fsn_mark->mask & FS_MODIFY))
1324 recalc = true;
1325 }
1326
1327 if (fsn_mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE ||
1328 want_iref == !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
1329 return recalc;
1330
1331 /*
1332 * NO_IREF may be removed from a mark, but not added.
1333 * When removed, fsnotify_recalc_mask() will take the inode ref.
1334 */
1335 WARN_ON_ONCE(!want_iref);
1336 fsn_mark->flags &= ~FSNOTIFY_MARK_FLAG_NO_IREF;
1337
1338 return true;
1339 }
1340
fanotify_mark_add_to_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int fan_flags)1341 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
1342 __u32 mask, unsigned int fan_flags)
1343 {
1344 bool recalc;
1345
1346 spin_lock(&fsn_mark->lock);
1347 if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
1348 fsn_mark->mask |= mask;
1349 else
1350 fsn_mark->ignore_mask |= mask;
1351
1352 recalc = fsnotify_calc_mask(fsn_mark) &
1353 ~fsnotify_conn_mask(fsn_mark->connector);
1354
1355 recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
1356 spin_unlock(&fsn_mark->lock);
1357
1358 return recalc;
1359 }
1360
1361 struct fan_fsid {
1362 struct super_block *sb;
1363 __kernel_fsid_t id;
1364 bool weak;
1365 };
1366
fanotify_set_mark_fsid(struct fsnotify_group * group,struct fsnotify_mark * mark,struct fan_fsid * fsid)1367 static int fanotify_set_mark_fsid(struct fsnotify_group *group,
1368 struct fsnotify_mark *mark,
1369 struct fan_fsid *fsid)
1370 {
1371 struct fsnotify_mark_connector *conn;
1372 struct fsnotify_mark *old;
1373 struct super_block *old_sb = NULL;
1374
1375 FANOTIFY_MARK(mark)->fsid = fsid->id;
1376 mark->flags |= FSNOTIFY_MARK_FLAG_HAS_FSID;
1377 if (fsid->weak)
1378 mark->flags |= FSNOTIFY_MARK_FLAG_WEAK_FSID;
1379
1380 /* First mark added will determine if group is single or multi fsid */
1381 if (list_empty(&group->marks_list))
1382 return 0;
1383
1384 /* Find sb of an existing mark */
1385 list_for_each_entry(old, &group->marks_list, g_list) {
1386 conn = READ_ONCE(old->connector);
1387 if (!conn)
1388 continue;
1389 old_sb = fsnotify_connector_sb(conn);
1390 if (old_sb)
1391 break;
1392 }
1393
1394 /* Only detached marks left? */
1395 if (!old_sb)
1396 return 0;
1397
1398 /* Do not allow mixing of marks with weak and strong fsid */
1399 if ((mark->flags ^ old->flags) & FSNOTIFY_MARK_FLAG_WEAK_FSID)
1400 return -EXDEV;
1401
1402 /* Allow mixing of marks with strong fsid from different fs */
1403 if (!fsid->weak)
1404 return 0;
1405
1406 /* Do not allow mixing marks with weak fsid from different fs */
1407 if (old_sb != fsid->sb)
1408 return -EXDEV;
1409
1410 /* Do not allow mixing marks from different btrfs sub-volumes */
1411 if (!fanotify_fsid_equal(&FANOTIFY_MARK(old)->fsid,
1412 &FANOTIFY_MARK(mark)->fsid))
1413 return -EXDEV;
1414
1415 return 0;
1416 }
1417
fanotify_add_new_mark(struct fsnotify_group * group,void * obj,unsigned int obj_type,unsigned int fan_flags,struct fan_fsid * fsid)1418 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
1419 void *obj,
1420 unsigned int obj_type,
1421 unsigned int fan_flags,
1422 struct fan_fsid *fsid)
1423 {
1424 struct ucounts *ucounts = group->fanotify_data.ucounts;
1425 struct fanotify_mark *fan_mark;
1426 struct fsnotify_mark *mark;
1427 int ret;
1428
1429 /*
1430 * Enforce per user marks limits per user in all containing user ns.
1431 * A group with FAN_UNLIMITED_MARKS does not contribute to mark count
1432 * in the limited groups account.
1433 */
1434 BUILD_BUG_ON(!(FANOTIFY_ADMIN_INIT_FLAGS & FAN_UNLIMITED_MARKS));
1435 if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS) &&
1436 !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
1437 return ERR_PTR(-ENOSPC);
1438
1439 fan_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
1440 if (!fan_mark) {
1441 ret = -ENOMEM;
1442 goto out_dec_ucounts;
1443 }
1444
1445 mark = &fan_mark->fsn_mark;
1446 fsnotify_init_mark(mark, group);
1447 if (fan_flags & FAN_MARK_EVICTABLE)
1448 mark->flags |= FSNOTIFY_MARK_FLAG_NO_IREF;
1449
1450 /* Cache fsid of filesystem containing the marked object */
1451 if (fsid) {
1452 ret = fanotify_set_mark_fsid(group, mark, fsid);
1453 if (ret)
1454 goto out_put_mark;
1455 } else {
1456 fan_mark->fsid.val[0] = fan_mark->fsid.val[1] = 0;
1457 }
1458
1459 ret = fsnotify_add_mark_locked(mark, obj, obj_type, 0);
1460 if (ret)
1461 goto out_put_mark;
1462
1463 return mark;
1464
1465 out_put_mark:
1466 fsnotify_put_mark(mark);
1467 out_dec_ucounts:
1468 if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS))
1469 dec_ucount(ucounts, UCOUNT_FANOTIFY_MARKS);
1470 return ERR_PTR(ret);
1471 }
1472
fanotify_group_init_error_pool(struct fsnotify_group * group)1473 static int fanotify_group_init_error_pool(struct fsnotify_group *group)
1474 {
1475 if (mempool_initialized(&group->fanotify_data.error_events_pool))
1476 return 0;
1477
1478 return mempool_init_kmalloc_pool(&group->fanotify_data.error_events_pool,
1479 FANOTIFY_DEFAULT_FEE_POOL_SIZE,
1480 sizeof(struct fanotify_error_event));
1481 }
1482
fanotify_may_update_existing_mark(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int fan_flags)1483 static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark,
1484 __u32 mask, unsigned int fan_flags)
1485 {
1486 /*
1487 * Non evictable mark cannot be downgraded to evictable mark.
1488 */
1489 if (fan_flags & FAN_MARK_EVICTABLE &&
1490 !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
1491 return -EEXIST;
1492
1493 /*
1494 * New ignore mask semantics cannot be downgraded to old semantics.
1495 */
1496 if (fan_flags & FAN_MARK_IGNORED_MASK &&
1497 fsn_mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
1498 return -EEXIST;
1499
1500 /*
1501 * An ignore mask that survives modify could never be downgraded to not
1502 * survive modify. With new FAN_MARK_IGNORE semantics we make that rule
1503 * explicit and return an error when trying to update the ignore mask
1504 * without the original FAN_MARK_IGNORED_SURV_MODIFY value.
1505 */
1506 if (fan_flags & FAN_MARK_IGNORE &&
1507 !(fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1508 fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
1509 return -EEXIST;
1510
1511 /* For now pre-content events are not generated for directories */
1512 mask |= fsn_mark->mask;
1513 if (mask & FANOTIFY_PRE_CONTENT_EVENTS && mask & FAN_ONDIR)
1514 return -EEXIST;
1515
1516 return 0;
1517 }
1518
fanotify_add_mark(struct fsnotify_group * group,void * obj,unsigned int obj_type,__u32 mask,unsigned int fan_flags,struct fan_fsid * fsid)1519 static int fanotify_add_mark(struct fsnotify_group *group,
1520 void *obj, unsigned int obj_type,
1521 __u32 mask, unsigned int fan_flags,
1522 struct fan_fsid *fsid)
1523 {
1524 struct fsnotify_mark *fsn_mark;
1525 bool recalc;
1526 int ret = 0;
1527
1528 fsnotify_group_lock(group);
1529 fsn_mark = fsnotify_find_mark(obj, obj_type, group);
1530 if (!fsn_mark) {
1531 fsn_mark = fanotify_add_new_mark(group, obj, obj_type,
1532 fan_flags, fsid);
1533 if (IS_ERR(fsn_mark)) {
1534 fsnotify_group_unlock(group);
1535 return PTR_ERR(fsn_mark);
1536 }
1537 }
1538
1539 /*
1540 * Check if requested mark flags conflict with an existing mark flags.
1541 */
1542 ret = fanotify_may_update_existing_mark(fsn_mark, mask, fan_flags);
1543 if (ret)
1544 goto out;
1545
1546 /*
1547 * Error events are pre-allocated per group, only if strictly
1548 * needed (i.e. FAN_FS_ERROR was requested).
1549 */
1550 if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS) &&
1551 (mask & FAN_FS_ERROR)) {
1552 ret = fanotify_group_init_error_pool(group);
1553 if (ret)
1554 goto out;
1555 }
1556
1557 recalc = fanotify_mark_add_to_mask(fsn_mark, mask, fan_flags);
1558 if (recalc)
1559 fsnotify_recalc_mask(fsn_mark->connector);
1560
1561 out:
1562 fsnotify_group_unlock(group);
1563
1564 fsnotify_put_mark(fsn_mark);
1565
1566 if (!ret && (mask & FANOTIFY_PERM_EVENTS))
1567 fanotify_perm_watchdog_group_add(group);
1568
1569 return ret;
1570 }
1571
fanotify_alloc_overflow_event(void)1572 static struct fsnotify_event *fanotify_alloc_overflow_event(void)
1573 {
1574 struct fanotify_event *oevent;
1575
1576 oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
1577 if (!oevent)
1578 return NULL;
1579
1580 fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
1581 oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
1582
1583 return &oevent->fse;
1584 }
1585
fanotify_alloc_merge_hash(void)1586 static struct hlist_head *fanotify_alloc_merge_hash(void)
1587 {
1588 struct hlist_head *hash;
1589
1590 hash = kmalloc(sizeof(struct hlist_head) << FANOTIFY_HTABLE_BITS,
1591 GFP_KERNEL_ACCOUNT);
1592 if (!hash)
1593 return NULL;
1594
1595 __hash_init(hash, FANOTIFY_HTABLE_SIZE);
1596
1597 return hash;
1598 }
1599
1600 /* fanotify syscalls */
SYSCALL_DEFINE2(fanotify_init,unsigned int,flags,unsigned int,event_f_flags)1601 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
1602 {
1603 struct user_namespace *user_ns = current_user_ns();
1604 struct fsnotify_group *group;
1605 int f_flags, fd;
1606 unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
1607 unsigned int class = flags & FANOTIFY_CLASS_BITS;
1608 unsigned int internal_flags = 0;
1609 struct file *file;
1610
1611 pr_debug("%s: flags=%x event_f_flags=%x\n",
1612 __func__, flags, event_f_flags);
1613
1614 if (!capable(CAP_SYS_ADMIN)) {
1615 /*
1616 * An unprivileged user can setup an fanotify group with
1617 * limited functionality - an unprivileged group is limited to
1618 * notification events with file handles or mount ids and it
1619 * cannot use unlimited queue/marks.
1620 */
1621 if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) ||
1622 !(flags & (FANOTIFY_FID_BITS | FAN_REPORT_MNT)))
1623 return -EPERM;
1624
1625 /*
1626 * Setting the internal flag FANOTIFY_UNPRIV on the group
1627 * prevents setting mount/filesystem marks on this group and
1628 * prevents reporting pid and open fd in events.
1629 */
1630 internal_flags |= FANOTIFY_UNPRIV;
1631 }
1632
1633 #ifdef CONFIG_AUDITSYSCALL
1634 if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
1635 #else
1636 if (flags & ~FANOTIFY_INIT_FLAGS)
1637 #endif
1638 return -EINVAL;
1639
1640 /*
1641 * A pidfd can only be returned for a thread-group leader; thus
1642 * FAN_REPORT_PIDFD and FAN_REPORT_TID need to remain mutually
1643 * exclusive.
1644 */
1645 if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
1646 return -EINVAL;
1647
1648 /* Don't allow mixing mnt events with inode events for now */
1649 if (flags & FAN_REPORT_MNT) {
1650 if (class != FAN_CLASS_NOTIF)
1651 return -EINVAL;
1652 if (flags & (FANOTIFY_FID_BITS | FAN_REPORT_FD_ERROR))
1653 return -EINVAL;
1654 }
1655
1656 if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
1657 return -EINVAL;
1658
1659 switch (event_f_flags & O_ACCMODE) {
1660 case O_RDONLY:
1661 case O_RDWR:
1662 case O_WRONLY:
1663 break;
1664 default:
1665 return -EINVAL;
1666 }
1667
1668 if (fid_mode && class != FAN_CLASS_NOTIF)
1669 return -EINVAL;
1670
1671 /*
1672 * Child name is reported with parent fid so requires dir fid.
1673 * We can report both child fid and dir fid with or without name.
1674 */
1675 if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
1676 return -EINVAL;
1677
1678 /*
1679 * FAN_REPORT_TARGET_FID requires FAN_REPORT_NAME and FAN_REPORT_FID
1680 * and is used as an indication to report both dir and child fid on all
1681 * dirent events.
1682 */
1683 if ((fid_mode & FAN_REPORT_TARGET_FID) &&
1684 (!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
1685 return -EINVAL;
1686
1687 f_flags = O_RDWR;
1688 if (flags & FAN_CLOEXEC)
1689 f_flags |= O_CLOEXEC;
1690 if (flags & FAN_NONBLOCK)
1691 f_flags |= O_NONBLOCK;
1692
1693 /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
1694 group = fsnotify_alloc_group(&fanotify_fsnotify_ops,
1695 FSNOTIFY_GROUP_USER);
1696 if (IS_ERR(group)) {
1697 return PTR_ERR(group);
1698 }
1699
1700 /* Enforce groups limits per user in all containing user ns */
1701 group->fanotify_data.ucounts = inc_ucount(user_ns, current_euid(),
1702 UCOUNT_FANOTIFY_GROUPS);
1703 if (!group->fanotify_data.ucounts) {
1704 fd = -EMFILE;
1705 goto out_destroy_group;
1706 }
1707
1708 group->fanotify_data.flags = flags | internal_flags;
1709 group->memcg = get_mem_cgroup_from_mm(current->mm);
1710 group->user_ns = get_user_ns(user_ns);
1711
1712 group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
1713 if (!group->fanotify_data.merge_hash) {
1714 fd = -ENOMEM;
1715 goto out_destroy_group;
1716 }
1717
1718 group->overflow_event = fanotify_alloc_overflow_event();
1719 if (unlikely(!group->overflow_event)) {
1720 fd = -ENOMEM;
1721 goto out_destroy_group;
1722 }
1723
1724 if (force_o_largefile())
1725 event_f_flags |= O_LARGEFILE;
1726 group->fanotify_data.f_flags = event_f_flags;
1727 init_waitqueue_head(&group->fanotify_data.access_waitq);
1728 INIT_LIST_HEAD(&group->fanotify_data.access_list);
1729 INIT_LIST_HEAD(&group->fanotify_data.perm_grp_list);
1730 switch (class) {
1731 case FAN_CLASS_NOTIF:
1732 group->priority = FSNOTIFY_PRIO_NORMAL;
1733 break;
1734 case FAN_CLASS_CONTENT:
1735 group->priority = FSNOTIFY_PRIO_CONTENT;
1736 break;
1737 case FAN_CLASS_PRE_CONTENT:
1738 group->priority = FSNOTIFY_PRIO_PRE_CONTENT;
1739 break;
1740 default:
1741 fd = -EINVAL;
1742 goto out_destroy_group;
1743 }
1744
1745 BUILD_BUG_ON(!(FANOTIFY_ADMIN_INIT_FLAGS & FAN_UNLIMITED_QUEUE));
1746 if (flags & FAN_UNLIMITED_QUEUE) {
1747 group->max_events = UINT_MAX;
1748 } else {
1749 group->max_events = fanotify_max_queued_events;
1750 }
1751
1752 if (flags & FAN_ENABLE_AUDIT) {
1753 fd = -EPERM;
1754 if (!capable(CAP_AUDIT_WRITE))
1755 goto out_destroy_group;
1756 }
1757
1758 fd = get_unused_fd_flags(f_flags);
1759 if (fd < 0)
1760 goto out_destroy_group;
1761
1762 file = anon_inode_getfile_fmode("[fanotify]", &fanotify_fops, group,
1763 f_flags, FMODE_NONOTIFY);
1764 if (IS_ERR(file)) {
1765 put_unused_fd(fd);
1766 fd = PTR_ERR(file);
1767 goto out_destroy_group;
1768 }
1769 fd_install(fd, file);
1770 return fd;
1771
1772 out_destroy_group:
1773 fsnotify_destroy_group(group);
1774 return fd;
1775 }
1776
fanotify_test_fsid(struct dentry * dentry,unsigned int flags,struct fan_fsid * fsid)1777 static int fanotify_test_fsid(struct dentry *dentry, unsigned int flags,
1778 struct fan_fsid *fsid)
1779 {
1780 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1781 __kernel_fsid_t root_fsid;
1782 int err;
1783
1784 /*
1785 * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
1786 */
1787 err = vfs_get_fsid(dentry, &fsid->id);
1788 if (err)
1789 return err;
1790
1791 fsid->sb = dentry->d_sb;
1792 if (!fsid->id.val[0] && !fsid->id.val[1]) {
1793 err = -ENODEV;
1794 goto weak;
1795 }
1796
1797 /*
1798 * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
1799 * which uses a different fsid than sb root.
1800 */
1801 err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
1802 if (err)
1803 return err;
1804
1805 if (!fanotify_fsid_equal(&root_fsid, &fsid->id)) {
1806 err = -EXDEV;
1807 goto weak;
1808 }
1809
1810 fsid->weak = false;
1811 return 0;
1812
1813 weak:
1814 /* Allow weak fsid when marking inodes */
1815 fsid->weak = true;
1816 return (mark_type == FAN_MARK_INODE) ? 0 : err;
1817 }
1818
1819 /* Check if filesystem can encode a unique fid */
fanotify_test_fid(struct dentry * dentry,unsigned int flags)1820 static int fanotify_test_fid(struct dentry *dentry, unsigned int flags)
1821 {
1822 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1823 const struct export_operations *nop = dentry->d_sb->s_export_op;
1824
1825 /*
1826 * We need to make sure that the filesystem supports encoding of
1827 * file handles so user can use name_to_handle_at() to compare fids
1828 * reported with events to the file handle of watched objects.
1829 */
1830 if (!exportfs_can_encode_fid(nop))
1831 return -EOPNOTSUPP;
1832
1833 /*
1834 * For sb/mount mark, we also need to make sure that the filesystem
1835 * supports decoding file handles, so user has a way to map back the
1836 * reported fids to filesystem objects.
1837 */
1838 if (mark_type != FAN_MARK_INODE && !exportfs_can_decode_fh(nop))
1839 return -EOPNOTSUPP;
1840
1841 return 0;
1842 }
1843
fanotify_events_supported(struct fsnotify_group * group,const struct path * path,__u64 mask,unsigned int flags)1844 static int fanotify_events_supported(struct fsnotify_group *group,
1845 const struct path *path, __u64 mask,
1846 unsigned int flags)
1847 {
1848 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1849 bool is_dir = d_is_dir(path->dentry);
1850 /* Strict validation of events in non-dir inode mask with v5.17+ APIs */
1851 bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
1852 (mask & FAN_RENAME) ||
1853 (flags & FAN_MARK_IGNORE);
1854
1855 /*
1856 * Filesystems need to opt-into pre-content evnets (a.k.a HSM)
1857 * and they are only supported on regular files and directories.
1858 */
1859 if (mask & FANOTIFY_PRE_CONTENT_EVENTS) {
1860 if (!(path->mnt->mnt_sb->s_iflags & SB_I_ALLOW_HSM))
1861 return -EOPNOTSUPP;
1862 if (!is_dir && !d_is_reg(path->dentry))
1863 return -EINVAL;
1864 }
1865
1866 /*
1867 * Some filesystems such as 'proc' acquire unusual locks when opening
1868 * files. For them fanotify permission events have high chances of
1869 * deadlocking the system - open done when reporting fanotify event
1870 * blocks on this "unusual" lock while another process holding the lock
1871 * waits for fanotify permission event to be answered. Just disallow
1872 * permission events for such filesystems.
1873 */
1874 if (mask & FANOTIFY_PERM_EVENTS &&
1875 path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
1876 return -EINVAL;
1877
1878 /*
1879 * mount and sb marks are not allowed on kernel internal pseudo fs,
1880 * like pipe_mnt, because that would subscribe to events on all the
1881 * anonynous pipes in the system.
1882 *
1883 * SB_NOUSER covers all of the internal pseudo fs whose objects are not
1884 * exposed to user's mount namespace, but there are other SB_KERNMOUNT
1885 * fs, like nsfs, debugfs, for which the value of allowing sb and mount
1886 * mark is questionable. For now we leave them alone.
1887 */
1888 if (mark_type != FAN_MARK_INODE &&
1889 path->mnt->mnt_sb->s_flags & SB_NOUSER)
1890 return -EINVAL;
1891
1892 /*
1893 * We shouldn't have allowed setting dirent events and the directory
1894 * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,
1895 * but because we always allowed it, error only when using new APIs.
1896 */
1897 if (strict_dir_events && mark_type == FAN_MARK_INODE &&
1898 !is_dir && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
1899 return -ENOTDIR;
1900
1901 return 0;
1902 }
1903
do_fanotify_mark(int fanotify_fd,unsigned int flags,__u64 mask,int dfd,const char __user * pathname)1904 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
1905 int dfd, const char __user *pathname)
1906 {
1907 struct inode *inode = NULL;
1908 struct fsnotify_group *group;
1909 struct path path;
1910 struct fan_fsid __fsid, *fsid = NULL;
1911 struct user_namespace *user_ns = NULL;
1912 struct mnt_namespace *mntns;
1913 u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
1914 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1915 unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;
1916 unsigned int ignore = flags & FANOTIFY_MARK_IGNORE_BITS;
1917 unsigned int obj_type, fid_mode;
1918 void *obj = NULL;
1919 u32 umask = 0;
1920 int ret;
1921
1922 pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
1923 __func__, fanotify_fd, flags, dfd, pathname, mask);
1924
1925 /* we only use the lower 32 bits as of right now. */
1926 if (upper_32_bits(mask))
1927 return -EINVAL;
1928
1929 if (flags & ~FANOTIFY_MARK_FLAGS)
1930 return -EINVAL;
1931
1932 switch (mark_type) {
1933 case FAN_MARK_INODE:
1934 obj_type = FSNOTIFY_OBJ_TYPE_INODE;
1935 break;
1936 case FAN_MARK_MOUNT:
1937 obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
1938 break;
1939 case FAN_MARK_FILESYSTEM:
1940 obj_type = FSNOTIFY_OBJ_TYPE_SB;
1941 break;
1942 case FAN_MARK_MNTNS:
1943 obj_type = FSNOTIFY_OBJ_TYPE_MNTNS;
1944 break;
1945 default:
1946 return -EINVAL;
1947 }
1948
1949 switch (mark_cmd) {
1950 case FAN_MARK_ADD:
1951 case FAN_MARK_REMOVE:
1952 if (!mask)
1953 return -EINVAL;
1954 break;
1955 case FAN_MARK_FLUSH:
1956 if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
1957 return -EINVAL;
1958 break;
1959 default:
1960 return -EINVAL;
1961 }
1962
1963 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1964 valid_mask |= FANOTIFY_PERM_EVENTS;
1965
1966 if (mask & ~valid_mask)
1967 return -EINVAL;
1968
1969
1970 /* We don't allow FAN_MARK_IGNORE & FAN_MARK_IGNORED_MASK together */
1971 if (ignore == (FAN_MARK_IGNORE | FAN_MARK_IGNORED_MASK))
1972 return -EINVAL;
1973
1974 /*
1975 * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with
1976 * FAN_MARK_IGNORED_MASK.
1977 */
1978 if (ignore == FAN_MARK_IGNORED_MASK) {
1979 mask &= ~FANOTIFY_EVENT_FLAGS;
1980 umask = FANOTIFY_EVENT_FLAGS;
1981 }
1982
1983 CLASS(fd, f)(fanotify_fd);
1984 if (fd_empty(f))
1985 return -EBADF;
1986
1987 /* verify that this is indeed an fanotify instance */
1988 if (unlikely(fd_file(f)->f_op != &fanotify_fops))
1989 return -EINVAL;
1990 group = fd_file(f)->private_data;
1991
1992 /* Only report mount events on mnt namespace */
1993 if (FAN_GROUP_FLAG(group, FAN_REPORT_MNT)) {
1994 if (mask & ~FANOTIFY_MOUNT_EVENTS)
1995 return -EINVAL;
1996 if (mark_type != FAN_MARK_MNTNS)
1997 return -EINVAL;
1998 } else {
1999 if (mask & FANOTIFY_MOUNT_EVENTS)
2000 return -EINVAL;
2001 if (mark_type == FAN_MARK_MNTNS)
2002 return -EINVAL;
2003 }
2004
2005 /*
2006 * A user is allowed to setup sb/mount/mntns marks only if it is
2007 * capable in the user ns where the group was created.
2008 */
2009 if (!ns_capable(group->user_ns, CAP_SYS_ADMIN) &&
2010 mark_type != FAN_MARK_INODE)
2011 return -EPERM;
2012
2013 /*
2014 * Permission events are not allowed for FAN_CLASS_NOTIF.
2015 * Pre-content permission events are not allowed for FAN_CLASS_CONTENT.
2016 */
2017 if (mask & FANOTIFY_PERM_EVENTS &&
2018 group->priority == FSNOTIFY_PRIO_NORMAL)
2019 return -EINVAL;
2020 else if (mask & FANOTIFY_PRE_CONTENT_EVENTS &&
2021 group->priority == FSNOTIFY_PRIO_CONTENT)
2022 return -EINVAL;
2023
2024 if (mask & FAN_FS_ERROR &&
2025 mark_type != FAN_MARK_FILESYSTEM)
2026 return -EINVAL;
2027
2028 /*
2029 * Evictable is only relevant for inode marks, because only inode object
2030 * can be evicted on memory pressure.
2031 */
2032 if (flags & FAN_MARK_EVICTABLE &&
2033 mark_type != FAN_MARK_INODE)
2034 return -EINVAL;
2035
2036 /*
2037 * Events that do not carry enough information to report
2038 * event->fd require a group that supports reporting fid. Those
2039 * events are not supported on a mount mark, because they do not
2040 * carry enough information (i.e. path) to be filtered by mount
2041 * point.
2042 */
2043 fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
2044 if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_MOUNT_EVENTS|FANOTIFY_EVENT_FLAGS) &&
2045 (!fid_mode || mark_type == FAN_MARK_MOUNT))
2046 return -EINVAL;
2047
2048 /*
2049 * FAN_RENAME uses special info type records to report the old and
2050 * new parent+name. Reporting only old and new parent id is less
2051 * useful and was not implemented.
2052 */
2053 if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
2054 return -EINVAL;
2055
2056 /* Pre-content events are not currently generated for directories. */
2057 if (mask & FANOTIFY_PRE_CONTENT_EVENTS && mask & FAN_ONDIR)
2058 return -EINVAL;
2059
2060 if (mark_cmd == FAN_MARK_FLUSH) {
2061 fsnotify_clear_marks_by_group(group, obj_type);
2062 return 0;
2063 }
2064
2065 ret = fanotify_find_path(dfd, pathname, &path, flags,
2066 (mask & ALL_FSNOTIFY_EVENTS), obj_type);
2067 if (ret)
2068 return ret;
2069
2070 if (mark_cmd == FAN_MARK_ADD) {
2071 ret = fanotify_events_supported(group, &path, mask, flags);
2072 if (ret)
2073 goto path_put_and_out;
2074 }
2075
2076 if (fid_mode) {
2077 ret = fanotify_test_fsid(path.dentry, flags, &__fsid);
2078 if (ret)
2079 goto path_put_and_out;
2080
2081 ret = fanotify_test_fid(path.dentry, flags);
2082 if (ret)
2083 goto path_put_and_out;
2084
2085 fsid = &__fsid;
2086 }
2087
2088 /*
2089 * In addition to being capable in the user ns where group was created,
2090 * the user also needs to be capable in the user ns associated with
2091 * the filesystem or in the user ns associated with the mntns
2092 * (when marking mntns).
2093 */
2094 if (obj_type == FSNOTIFY_OBJ_TYPE_INODE) {
2095 inode = path.dentry->d_inode;
2096 obj = inode;
2097 } else if (obj_type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
2098 user_ns = path.mnt->mnt_sb->s_user_ns;
2099 obj = path.mnt;
2100 } else if (obj_type == FSNOTIFY_OBJ_TYPE_SB) {
2101 user_ns = path.mnt->mnt_sb->s_user_ns;
2102 obj = path.mnt->mnt_sb;
2103 } else if (obj_type == FSNOTIFY_OBJ_TYPE_MNTNS) {
2104 ret = -EINVAL;
2105 mntns = mnt_ns_from_dentry(path.dentry);
2106 if (!mntns)
2107 goto path_put_and_out;
2108 user_ns = mntns->user_ns;
2109 obj = mntns;
2110 }
2111
2112 ret = -EPERM;
2113 if (user_ns && !ns_capable(user_ns, CAP_SYS_ADMIN))
2114 goto path_put_and_out;
2115
2116 ret = -EINVAL;
2117 if (!obj)
2118 goto path_put_and_out;
2119
2120 /*
2121 * If some other task has this inode open for write we should not add
2122 * an ignore mask, unless that ignore mask is supposed to survive
2123 * modification changes anyway.
2124 */
2125 if (mark_cmd == FAN_MARK_ADD && (flags & FANOTIFY_MARK_IGNORE_BITS) &&
2126 !(flags & FAN_MARK_IGNORED_SURV_MODIFY)) {
2127 ret = !inode ? -EINVAL : -EISDIR;
2128 /* FAN_MARK_IGNORE requires SURV_MODIFY for sb/mount/dir marks */
2129 if (ignore == FAN_MARK_IGNORE &&
2130 (!inode || S_ISDIR(inode->i_mode)))
2131 goto path_put_and_out;
2132
2133 ret = 0;
2134 if (inode && inode_is_open_for_write(inode))
2135 goto path_put_and_out;
2136 }
2137
2138 /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
2139 if (!inode || !S_ISDIR(inode->i_mode)) {
2140 mask &= ~FAN_EVENT_ON_CHILD;
2141 umask = FAN_EVENT_ON_CHILD;
2142 /*
2143 * If group needs to report parent fid, register for getting
2144 * events with parent/name info for non-directory.
2145 */
2146 if ((fid_mode & FAN_REPORT_DIR_FID) &&
2147 (flags & FAN_MARK_ADD) && !ignore)
2148 mask |= FAN_EVENT_ON_CHILD;
2149 }
2150
2151 /* create/update an inode mark */
2152 switch (mark_cmd) {
2153 case FAN_MARK_ADD:
2154 ret = fanotify_add_mark(group, obj, obj_type, mask, flags,
2155 fsid);
2156 break;
2157 case FAN_MARK_REMOVE:
2158 ret = fanotify_remove_mark(group, obj, obj_type, mask, flags,
2159 umask);
2160 break;
2161 default:
2162 ret = -EINVAL;
2163 }
2164
2165 path_put_and_out:
2166 path_put(&path);
2167 return ret;
2168 }
2169
2170 #ifndef CONFIG_ARCH_SPLIT_ARG64
SYSCALL_DEFINE5(fanotify_mark,int,fanotify_fd,unsigned int,flags,__u64,mask,int,dfd,const char __user *,pathname)2171 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
2172 __u64, mask, int, dfd,
2173 const char __user *, pathname)
2174 {
2175 return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
2176 }
2177 #endif
2178
2179 #if defined(CONFIG_ARCH_SPLIT_ARG64) || defined(CONFIG_COMPAT)
SYSCALL32_DEFINE6(fanotify_mark,int,fanotify_fd,unsigned int,flags,SC_ARG64 (mask),int,dfd,const char __user *,pathname)2180 SYSCALL32_DEFINE6(fanotify_mark,
2181 int, fanotify_fd, unsigned int, flags,
2182 SC_ARG64(mask), int, dfd,
2183 const char __user *, pathname)
2184 {
2185 return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask),
2186 dfd, pathname);
2187 }
2188 #endif
2189
2190 /*
2191 * fanotify_user_setup - Our initialization function. Note that we cannot return
2192 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
2193 * must result in panic().
2194 */
fanotify_user_setup(void)2195 static int __init fanotify_user_setup(void)
2196 {
2197 struct sysinfo si;
2198 int max_marks;
2199
2200 si_meminfo(&si);
2201 /*
2202 * Allow up to 1% of addressable memory to be accounted for per user
2203 * marks limited to the range [8192, 1048576]. mount and sb marks are
2204 * a lot cheaper than inode marks, but there is no reason for a user
2205 * to have many of those, so calculate by the cost of inode marks.
2206 */
2207 max_marks = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) /
2208 INODE_MARK_COST;
2209 max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
2210 FANOTIFY_DEFAULT_MAX_USER_MARKS);
2211
2212 BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
2213 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 14);
2214 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);
2215
2216 fanotify_mark_cache = KMEM_CACHE(fanotify_mark,
2217 SLAB_PANIC|SLAB_ACCOUNT);
2218 fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
2219 SLAB_PANIC);
2220 fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
2221 SLAB_PANIC);
2222 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
2223 fanotify_perm_event_cachep =
2224 KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
2225 }
2226 fanotify_mnt_event_cachep = KMEM_CACHE(fanotify_mnt_event, SLAB_PANIC);
2227
2228 fanotify_max_queued_events = FANOTIFY_DEFAULT_MAX_EVENTS;
2229 init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS] =
2230 FANOTIFY_DEFAULT_MAX_GROUPS;
2231 init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS] = max_marks;
2232 fanotify_sysctls_init();
2233
2234 return 0;
2235 }
2236 device_initcall(fanotify_user_setup);
2237