1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/fanotify.h>
3 #include <linux/fcntl.h>
4 #include <linux/fdtable.h>
5 #include <linux/file.h>
6 #include <linux/fs.h>
7 #include <linux/anon_inodes.h>
8 #include <linux/fsnotify_backend.h>
9 #include <linux/init.h>
10 #include <linux/mount.h>
11 #include <linux/namei.h>
12 #include <linux/poll.h>
13 #include <linux/security.h>
14 #include <linux/syscalls.h>
15 #include <linux/slab.h>
16 #include <linux/types.h>
17 #include <linux/uaccess.h>
18 #include <linux/compat.h>
19 #include <linux/sched/signal.h>
20 #include <linux/memcontrol.h>
21 #include <linux/statfs.h>
22 #include <linux/exportfs.h>
23
24 #include <asm/ioctls.h>
25
26 #include "../../mount.h"
27 #include "../fdinfo.h"
28 #include "fanotify.h"
29
30 #define FANOTIFY_DEFAULT_MAX_EVENTS 16384
31 #define FANOTIFY_OLD_DEFAULT_MAX_MARKS 8192
32 #define FANOTIFY_DEFAULT_MAX_GROUPS 128
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
54 #ifdef CONFIG_SYSCTL
55
56 #include <linux/sysctl.h>
57
58 static long ft_zero = 0;
59 static long ft_int_max = INT_MAX;
60
61 struct ctl_table fanotify_table[] = {
62 {
63 .procname = "max_user_groups",
64 .data = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS],
65 .maxlen = sizeof(long),
66 .mode = 0644,
67 .proc_handler = proc_doulongvec_minmax,
68 .extra1 = &ft_zero,
69 .extra2 = &ft_int_max,
70 },
71 {
72 .procname = "max_user_marks",
73 .data = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS],
74 .maxlen = sizeof(long),
75 .mode = 0644,
76 .proc_handler = proc_doulongvec_minmax,
77 .extra1 = &ft_zero,
78 .extra2 = &ft_int_max,
79 },
80 {
81 .procname = "max_queued_events",
82 .data = &fanotify_max_queued_events,
83 .maxlen = sizeof(int),
84 .mode = 0644,
85 .proc_handler = proc_dointvec_minmax,
86 .extra1 = SYSCTL_ZERO
87 },
88 { }
89 };
90 #endif /* CONFIG_SYSCTL */
91
92 /*
93 * All flags that may be specified in parameter event_f_flags of fanotify_init.
94 *
95 * Internal and external open flags are stored together in field f_flags of
96 * struct file. Only external open flags shall be allowed in event_f_flags.
97 * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
98 * excluded.
99 */
100 #define FANOTIFY_INIT_ALL_EVENT_F_BITS ( \
101 O_ACCMODE | O_APPEND | O_NONBLOCK | \
102 __O_SYNC | O_DSYNC | O_CLOEXEC | \
103 O_LARGEFILE | O_NOATIME )
104
105 extern const struct fsnotify_ops fanotify_fsnotify_ops;
106
107 struct kmem_cache *fanotify_mark_cache __read_mostly;
108 struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
109 struct kmem_cache *fanotify_path_event_cachep __read_mostly;
110 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
111
112 #define FANOTIFY_EVENT_ALIGN 4
113 #define FANOTIFY_FID_INFO_HDR_LEN \
114 (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
115 #define FANOTIFY_PIDFD_INFO_HDR_LEN \
116 sizeof(struct fanotify_event_info_pidfd)
117
fanotify_fid_info_len(int fh_len,int name_len)118 static int fanotify_fid_info_len(int fh_len, int name_len)
119 {
120 int info_len = fh_len;
121
122 if (name_len)
123 info_len += name_len + 1;
124
125 return roundup(FANOTIFY_FID_INFO_HDR_LEN + info_len,
126 FANOTIFY_EVENT_ALIGN);
127 }
128
fanotify_event_info_len(unsigned int info_mode,struct fanotify_event * event)129 static int fanotify_event_info_len(unsigned int info_mode,
130 struct fanotify_event *event)
131 {
132 struct fanotify_info *info = fanotify_event_info(event);
133 int dir_fh_len = fanotify_event_dir_fh_len(event);
134 int fh_len = fanotify_event_object_fh_len(event);
135 int info_len = 0;
136 int dot_len = 0;
137
138 if (dir_fh_len) {
139 info_len += fanotify_fid_info_len(dir_fh_len, info->name_len);
140 } else if ((info_mode & FAN_REPORT_NAME) &&
141 (event->mask & FAN_ONDIR)) {
142 /*
143 * With group flag FAN_REPORT_NAME, if name was not recorded in
144 * event on a directory, we will report the name ".".
145 */
146 dot_len = 1;
147 }
148
149 if (info_mode & FAN_REPORT_PIDFD)
150 info_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
151
152 if (fh_len)
153 info_len += fanotify_fid_info_len(fh_len, dot_len);
154
155 return info_len;
156 }
157
158 /*
159 * Remove an hashed event from merge hash table.
160 */
fanotify_unhash_event(struct fsnotify_group * group,struct fanotify_event * event)161 static void fanotify_unhash_event(struct fsnotify_group *group,
162 struct fanotify_event *event)
163 {
164 assert_spin_locked(&group->notification_lock);
165
166 pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
167 group, event, fanotify_event_hash_bucket(group, event));
168
169 if (WARN_ON_ONCE(hlist_unhashed(&event->merge_list)))
170 return;
171
172 hlist_del_init(&event->merge_list);
173 }
174
175 /*
176 * Get an fanotify notification event if one exists and is small
177 * enough to fit in "count". Return an error pointer if the count
178 * is not large enough. When permission event is dequeued, its state is
179 * updated accordingly.
180 */
get_one_event(struct fsnotify_group * group,size_t count)181 static struct fanotify_event *get_one_event(struct fsnotify_group *group,
182 size_t count)
183 {
184 size_t event_size = FAN_EVENT_METADATA_LEN;
185 struct fanotify_event *event = NULL;
186 struct fsnotify_event *fsn_event;
187 unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
188
189 pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
190
191 spin_lock(&group->notification_lock);
192 fsn_event = fsnotify_peek_first_event(group);
193 if (!fsn_event)
194 goto out;
195
196 event = FANOTIFY_E(fsn_event);
197 if (info_mode)
198 event_size += fanotify_event_info_len(info_mode, event);
199
200 if (event_size > count) {
201 event = ERR_PTR(-EINVAL);
202 goto out;
203 }
204
205 /*
206 * Held the notification_lock the whole time, so this is the
207 * same event we peeked above.
208 */
209 fsnotify_remove_first_event(group);
210 if (fanotify_is_perm_event(event->mask))
211 FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
212 if (fanotify_is_hashed_event(event->mask))
213 fanotify_unhash_event(group, event);
214 out:
215 spin_unlock(&group->notification_lock);
216 return event;
217 }
218
create_fd(struct fsnotify_group * group,struct path * path,struct file ** file)219 static int create_fd(struct fsnotify_group *group, struct path *path,
220 struct file **file)
221 {
222 int client_fd;
223 struct file *new_file;
224
225 client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
226 if (client_fd < 0)
227 return client_fd;
228
229 /*
230 * we need a new file handle for the userspace program so it can read even if it was
231 * originally opened O_WRONLY.
232 */
233 new_file = dentry_open(path,
234 group->fanotify_data.f_flags | FMODE_NONOTIFY,
235 current_cred());
236 if (IS_ERR(new_file)) {
237 /*
238 * we still send an event even if we can't open the file. this
239 * can happen when say tasks are gone and we try to open their
240 * /proc files or we try to open a WRONLY file like in sysfs
241 * we just send the errno to userspace since there isn't much
242 * else we can do.
243 */
244 put_unused_fd(client_fd);
245 client_fd = PTR_ERR(new_file);
246 } else {
247 *file = new_file;
248 }
249
250 return client_fd;
251 }
252
253 /*
254 * Finish processing of permission event by setting it to ANSWERED state and
255 * drop group->notification_lock.
256 */
finish_permission_event(struct fsnotify_group * group,struct fanotify_perm_event * event,unsigned int response)257 static void finish_permission_event(struct fsnotify_group *group,
258 struct fanotify_perm_event *event,
259 unsigned int response)
260 __releases(&group->notification_lock)
261 {
262 bool destroy = false;
263
264 assert_spin_locked(&group->notification_lock);
265 event->response = response;
266 if (event->state == FAN_EVENT_CANCELED)
267 destroy = true;
268 else
269 event->state = FAN_EVENT_ANSWERED;
270 spin_unlock(&group->notification_lock);
271 if (destroy)
272 fsnotify_destroy_event(group, &event->fae.fse);
273 }
274
process_access_response(struct fsnotify_group * group,struct fanotify_response * response_struct)275 static int process_access_response(struct fsnotify_group *group,
276 struct fanotify_response *response_struct)
277 {
278 struct fanotify_perm_event *event;
279 int fd = response_struct->fd;
280 int response = response_struct->response;
281
282 pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
283 fd, response);
284 /*
285 * make sure the response is valid, if invalid we do nothing and either
286 * userspace can send a valid response or we will clean it up after the
287 * timeout
288 */
289 switch (response & ~FAN_AUDIT) {
290 case FAN_ALLOW:
291 case FAN_DENY:
292 break;
293 default:
294 return -EINVAL;
295 }
296
297 if (fd < 0)
298 return -EINVAL;
299
300 if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
301 return -EINVAL;
302
303 spin_lock(&group->notification_lock);
304 list_for_each_entry(event, &group->fanotify_data.access_list,
305 fae.fse.list) {
306 if (event->fd != fd)
307 continue;
308
309 list_del_init(&event->fae.fse.list);
310 finish_permission_event(group, event, response);
311 wake_up(&group->fanotify_data.access_waitq);
312 return 0;
313 }
314 spin_unlock(&group->notification_lock);
315
316 return -ENOENT;
317 }
318
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)319 static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
320 int info_type, const char *name,
321 size_t name_len,
322 char __user *buf, size_t count)
323 {
324 struct fanotify_event_info_fid info = { };
325 struct file_handle handle = { };
326 unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf;
327 size_t fh_len = fh ? fh->len : 0;
328 size_t info_len = fanotify_fid_info_len(fh_len, name_len);
329 size_t len = info_len;
330
331 pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
332 __func__, fh_len, name_len, info_len, count);
333
334 if (!fh_len)
335 return 0;
336
337 if (WARN_ON_ONCE(len < sizeof(info) || len > count))
338 return -EFAULT;
339
340 /*
341 * Copy event info fid header followed by variable sized file handle
342 * and optionally followed by variable sized filename.
343 */
344 switch (info_type) {
345 case FAN_EVENT_INFO_TYPE_FID:
346 case FAN_EVENT_INFO_TYPE_DFID:
347 if (WARN_ON_ONCE(name_len))
348 return -EFAULT;
349 break;
350 case FAN_EVENT_INFO_TYPE_DFID_NAME:
351 if (WARN_ON_ONCE(!name || !name_len))
352 return -EFAULT;
353 break;
354 default:
355 return -EFAULT;
356 }
357
358 info.hdr.info_type = info_type;
359 info.hdr.len = len;
360 info.fsid = *fsid;
361 if (copy_to_user(buf, &info, sizeof(info)))
362 return -EFAULT;
363
364 buf += sizeof(info);
365 len -= sizeof(info);
366 if (WARN_ON_ONCE(len < sizeof(handle)))
367 return -EFAULT;
368
369 handle.handle_type = fh->type;
370 handle.handle_bytes = fh_len;
371 if (copy_to_user(buf, &handle, sizeof(handle)))
372 return -EFAULT;
373
374 buf += sizeof(handle);
375 len -= sizeof(handle);
376 if (WARN_ON_ONCE(len < fh_len))
377 return -EFAULT;
378
379 /*
380 * For an inline fh and inline file name, copy through stack to exclude
381 * the copy from usercopy hardening protections.
382 */
383 fh_buf = fanotify_fh_buf(fh);
384 if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
385 memcpy(bounce, fh_buf, fh_len);
386 fh_buf = bounce;
387 }
388 if (copy_to_user(buf, fh_buf, fh_len))
389 return -EFAULT;
390
391 buf += fh_len;
392 len -= fh_len;
393
394 if (name_len) {
395 /* Copy the filename with terminating null */
396 name_len++;
397 if (WARN_ON_ONCE(len < name_len))
398 return -EFAULT;
399
400 if (copy_to_user(buf, name, name_len))
401 return -EFAULT;
402
403 buf += name_len;
404 len -= name_len;
405 }
406
407 /* Pad with 0's */
408 WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
409 if (len > 0 && clear_user(buf, len))
410 return -EFAULT;
411
412 return info_len;
413 }
414
copy_pidfd_info_to_user(int pidfd,char __user * buf,size_t count)415 static int copy_pidfd_info_to_user(int pidfd,
416 char __user *buf,
417 size_t count)
418 {
419 struct fanotify_event_info_pidfd info = { };
420 size_t info_len = FANOTIFY_PIDFD_INFO_HDR_LEN;
421
422 if (WARN_ON_ONCE(info_len > count))
423 return -EFAULT;
424
425 info.hdr.info_type = FAN_EVENT_INFO_TYPE_PIDFD;
426 info.hdr.len = info_len;
427 info.pidfd = pidfd;
428
429 if (copy_to_user(buf, &info, info_len))
430 return -EFAULT;
431
432 return info_len;
433 }
434
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)435 static int copy_info_records_to_user(struct fanotify_event *event,
436 struct fanotify_info *info,
437 unsigned int info_mode, int pidfd,
438 char __user *buf, size_t count)
439 {
440 int ret, total_bytes = 0, info_type = 0;
441 unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;
442 unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
443
444 /*
445 * Event info records order is as follows: dir fid + name, child fid.
446 */
447 if (fanotify_event_dir_fh_len(event)) {
448 info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
449 FAN_EVENT_INFO_TYPE_DFID;
450 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
451 fanotify_info_dir_fh(info),
452 info_type,
453 fanotify_info_name(info),
454 info->name_len, buf, count);
455 if (ret < 0)
456 return ret;
457
458 buf += ret;
459 count -= ret;
460 total_bytes += ret;
461 }
462
463 if (fanotify_event_object_fh_len(event)) {
464 const char *dot = NULL;
465 int dot_len = 0;
466
467 if (fid_mode == FAN_REPORT_FID || info_type) {
468 /*
469 * With only group flag FAN_REPORT_FID only type FID is
470 * reported. Second info record type is always FID.
471 */
472 info_type = FAN_EVENT_INFO_TYPE_FID;
473 } else if ((fid_mode & FAN_REPORT_NAME) &&
474 (event->mask & FAN_ONDIR)) {
475 /*
476 * With group flag FAN_REPORT_NAME, if name was not
477 * recorded in an event on a directory, report the name
478 * "." with info type DFID_NAME.
479 */
480 info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
481 dot = ".";
482 dot_len = 1;
483 } else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
484 (event->mask & FAN_ONDIR)) {
485 /*
486 * With group flag FAN_REPORT_DIR_FID, a single info
487 * record has type DFID for directory entry modification
488 * event and for event on a directory.
489 */
490 info_type = FAN_EVENT_INFO_TYPE_DFID;
491 } else {
492 /*
493 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,
494 * a single info record has type FID for event on a
495 * non-directory, when there is no directory to report.
496 * For example, on FAN_DELETE_SELF event.
497 */
498 info_type = FAN_EVENT_INFO_TYPE_FID;
499 }
500
501 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
502 fanotify_event_object_fh(event),
503 info_type, dot, dot_len,
504 buf, count);
505 if (ret < 0)
506 return ret;
507
508 buf += ret;
509 count -= ret;
510 total_bytes += ret;
511 }
512
513 if (pidfd_mode) {
514 ret = copy_pidfd_info_to_user(pidfd, buf, count);
515 if (ret < 0)
516 return ret;
517
518 buf += ret;
519 count -= ret;
520 total_bytes += ret;
521 }
522
523 return total_bytes;
524 }
525
copy_event_to_user(struct fsnotify_group * group,struct fanotify_event * event,char __user * buf,size_t count)526 static ssize_t copy_event_to_user(struct fsnotify_group *group,
527 struct fanotify_event *event,
528 char __user *buf, size_t count)
529 {
530 struct fanotify_event_metadata metadata;
531 struct path *path = fanotify_event_path(event);
532 struct fanotify_info *info = fanotify_event_info(event);
533 unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
534 unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
535 struct file *f = NULL;
536 int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD;
537
538 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
539
540 metadata.event_len = FAN_EVENT_METADATA_LEN +
541 fanotify_event_info_len(info_mode, event);
542 metadata.metadata_len = FAN_EVENT_METADATA_LEN;
543 metadata.vers = FANOTIFY_METADATA_VERSION;
544 metadata.reserved = 0;
545 metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
546 metadata.pid = pid_vnr(event->pid);
547 /*
548 * For an unprivileged listener, event->pid can be used to identify the
549 * events generated by the listener process itself, without disclosing
550 * the pids of other processes.
551 */
552 if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
553 task_tgid(current) != event->pid)
554 metadata.pid = 0;
555
556 /*
557 * For now, fid mode is required for an unprivileged listener and
558 * fid mode does not report fd in events. Keep this check anyway
559 * for safety in case fid mode requirement is relaxed in the future
560 * to allow unprivileged listener to get events with no fd and no fid.
561 */
562 if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
563 path && path->mnt && path->dentry) {
564 fd = create_fd(group, path, &f);
565 if (fd < 0)
566 return fd;
567 }
568 metadata.fd = fd;
569
570 if (pidfd_mode) {
571 /*
572 * Complain if the FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
573 * exclusion is ever lifted. At the time of incoporating pidfd
574 * support within fanotify, the pidfd API only supported the
575 * creation of pidfds for thread-group leaders.
576 */
577 WARN_ON_ONCE(FAN_GROUP_FLAG(group, FAN_REPORT_TID));
578
579 /*
580 * The PIDTYPE_TGID check for an event->pid is performed
581 * preemptively in an attempt to catch out cases where the event
582 * listener reads events after the event generating process has
583 * already terminated. Report FAN_NOPIDFD to the event listener
584 * in those cases, with all other pidfd creation errors being
585 * reported as FAN_EPIDFD.
586 */
587 if (metadata.pid == 0 ||
588 !pid_has_task(event->pid, PIDTYPE_TGID)) {
589 pidfd = FAN_NOPIDFD;
590 } else {
591 pidfd = pidfd_create(event->pid, 0);
592 if (pidfd < 0)
593 pidfd = FAN_EPIDFD;
594 }
595 }
596
597 ret = -EFAULT;
598 /*
599 * Sanity check copy size in case get_one_event() and
600 * event_len sizes ever get out of sync.
601 */
602 if (WARN_ON_ONCE(metadata.event_len > count))
603 goto out_close_fd;
604
605 if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
606 goto out_close_fd;
607
608 buf += FAN_EVENT_METADATA_LEN;
609 count -= FAN_EVENT_METADATA_LEN;
610
611 if (fanotify_is_perm_event(event->mask))
612 FANOTIFY_PERM(event)->fd = fd;
613
614 if (f)
615 fd_install(fd, f);
616
617 if (info_mode) {
618 ret = copy_info_records_to_user(event, info, info_mode, pidfd,
619 buf, count);
620 if (ret < 0)
621 goto out_close_fd;
622 }
623
624 return metadata.event_len;
625
626 out_close_fd:
627 if (fd != FAN_NOFD) {
628 put_unused_fd(fd);
629 fput(f);
630 }
631
632 if (pidfd >= 0)
633 close_fd(pidfd);
634
635 return ret;
636 }
637
638 /* intofiy userspace file descriptor functions */
fanotify_poll(struct file * file,poll_table * wait)639 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
640 {
641 struct fsnotify_group *group = file->private_data;
642 __poll_t ret = 0;
643
644 poll_wait(file, &group->notification_waitq, wait);
645 spin_lock(&group->notification_lock);
646 if (!fsnotify_notify_queue_is_empty(group))
647 ret = EPOLLIN | EPOLLRDNORM;
648 spin_unlock(&group->notification_lock);
649
650 return ret;
651 }
652
fanotify_read(struct file * file,char __user * buf,size_t count,loff_t * pos)653 static ssize_t fanotify_read(struct file *file, char __user *buf,
654 size_t count, loff_t *pos)
655 {
656 struct fsnotify_group *group;
657 struct fanotify_event *event;
658 char __user *start;
659 int ret;
660 DEFINE_WAIT_FUNC(wait, woken_wake_function);
661
662 start = buf;
663 group = file->private_data;
664
665 pr_debug("%s: group=%p\n", __func__, group);
666
667 add_wait_queue(&group->notification_waitq, &wait);
668 while (1) {
669 /*
670 * User can supply arbitrarily large buffer. Avoid softlockups
671 * in case there are lots of available events.
672 */
673 cond_resched();
674 event = get_one_event(group, count);
675 if (IS_ERR(event)) {
676 ret = PTR_ERR(event);
677 break;
678 }
679
680 if (!event) {
681 ret = -EAGAIN;
682 if (file->f_flags & O_NONBLOCK)
683 break;
684
685 ret = -ERESTARTSYS;
686 if (signal_pending(current))
687 break;
688
689 if (start != buf)
690 break;
691
692 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
693 continue;
694 }
695
696 ret = copy_event_to_user(group, event, buf, count);
697 if (unlikely(ret == -EOPENSTALE)) {
698 /*
699 * We cannot report events with stale fd so drop it.
700 * Setting ret to 0 will continue the event loop and
701 * do the right thing if there are no more events to
702 * read (i.e. return bytes read, -EAGAIN or wait).
703 */
704 ret = 0;
705 }
706
707 /*
708 * Permission events get queued to wait for response. Other
709 * events can be destroyed now.
710 */
711 if (!fanotify_is_perm_event(event->mask)) {
712 fsnotify_destroy_event(group, &event->fse);
713 } else {
714 if (ret <= 0) {
715 spin_lock(&group->notification_lock);
716 finish_permission_event(group,
717 FANOTIFY_PERM(event), FAN_DENY);
718 wake_up(&group->fanotify_data.access_waitq);
719 } else {
720 spin_lock(&group->notification_lock);
721 list_add_tail(&event->fse.list,
722 &group->fanotify_data.access_list);
723 spin_unlock(&group->notification_lock);
724 }
725 }
726 if (ret < 0)
727 break;
728 buf += ret;
729 count -= ret;
730 }
731 remove_wait_queue(&group->notification_waitq, &wait);
732
733 if (start != buf && ret != -EFAULT)
734 ret = buf - start;
735 return ret;
736 }
737
fanotify_write(struct file * file,const char __user * buf,size_t count,loff_t * pos)738 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
739 {
740 struct fanotify_response response = { .fd = -1, .response = -1 };
741 struct fsnotify_group *group;
742 int ret;
743
744 if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
745 return -EINVAL;
746
747 group = file->private_data;
748
749 if (count < sizeof(response))
750 return -EINVAL;
751
752 count = sizeof(response);
753
754 pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
755
756 if (copy_from_user(&response, buf, count))
757 return -EFAULT;
758
759 ret = process_access_response(group, &response);
760 if (ret < 0)
761 count = ret;
762
763 return count;
764 }
765
fanotify_release(struct inode * ignored,struct file * file)766 static int fanotify_release(struct inode *ignored, struct file *file)
767 {
768 struct fsnotify_group *group = file->private_data;
769 struct fsnotify_event *fsn_event;
770
771 /*
772 * Stop new events from arriving in the notification queue. since
773 * userspace cannot use fanotify fd anymore, no event can enter or
774 * leave access_list by now either.
775 */
776 fsnotify_group_stop_queueing(group);
777
778 /*
779 * Process all permission events on access_list and notification queue
780 * and simulate reply from userspace.
781 */
782 spin_lock(&group->notification_lock);
783 while (!list_empty(&group->fanotify_data.access_list)) {
784 struct fanotify_perm_event *event;
785
786 event = list_first_entry(&group->fanotify_data.access_list,
787 struct fanotify_perm_event, fae.fse.list);
788 list_del_init(&event->fae.fse.list);
789 finish_permission_event(group, event, FAN_ALLOW);
790 spin_lock(&group->notification_lock);
791 }
792
793 /*
794 * Destroy all non-permission events. For permission events just
795 * dequeue them and set the response. They will be freed once the
796 * response is consumed and fanotify_get_response() returns.
797 */
798 while ((fsn_event = fsnotify_remove_first_event(group))) {
799 struct fanotify_event *event = FANOTIFY_E(fsn_event);
800
801 if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
802 spin_unlock(&group->notification_lock);
803 fsnotify_destroy_event(group, fsn_event);
804 } else {
805 finish_permission_event(group, FANOTIFY_PERM(event),
806 FAN_ALLOW);
807 }
808 spin_lock(&group->notification_lock);
809 }
810 spin_unlock(&group->notification_lock);
811
812 /* Response for all permission events it set, wakeup waiters */
813 wake_up(&group->fanotify_data.access_waitq);
814
815 /* matches the fanotify_init->fsnotify_alloc_group */
816 fsnotify_destroy_group(group);
817
818 return 0;
819 }
820
fanotify_ioctl(struct file * file,unsigned int cmd,unsigned long arg)821 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
822 {
823 struct fsnotify_group *group;
824 struct fsnotify_event *fsn_event;
825 void __user *p;
826 int ret = -ENOTTY;
827 size_t send_len = 0;
828
829 group = file->private_data;
830
831 p = (void __user *) arg;
832
833 switch (cmd) {
834 case FIONREAD:
835 spin_lock(&group->notification_lock);
836 list_for_each_entry(fsn_event, &group->notification_list, list)
837 send_len += FAN_EVENT_METADATA_LEN;
838 spin_unlock(&group->notification_lock);
839 ret = put_user(send_len, (int __user *) p);
840 break;
841 }
842
843 return ret;
844 }
845
846 static const struct file_operations fanotify_fops = {
847 .show_fdinfo = fanotify_show_fdinfo,
848 .poll = fanotify_poll,
849 .read = fanotify_read,
850 .write = fanotify_write,
851 .fasync = NULL,
852 .release = fanotify_release,
853 .unlocked_ioctl = fanotify_ioctl,
854 .compat_ioctl = compat_ptr_ioctl,
855 .llseek = noop_llseek,
856 };
857
fanotify_find_path(int dfd,const char __user * filename,struct path * path,unsigned int flags,__u64 mask,unsigned int obj_type)858 static int fanotify_find_path(int dfd, const char __user *filename,
859 struct path *path, unsigned int flags, __u64 mask,
860 unsigned int obj_type)
861 {
862 int ret;
863
864 pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
865 dfd, filename, flags);
866
867 if (filename == NULL) {
868 struct fd f = fdget(dfd);
869
870 ret = -EBADF;
871 if (!f.file)
872 goto out;
873
874 ret = -ENOTDIR;
875 if ((flags & FAN_MARK_ONLYDIR) &&
876 !(S_ISDIR(file_inode(f.file)->i_mode))) {
877 fdput(f);
878 goto out;
879 }
880
881 *path = f.file->f_path;
882 path_get(path);
883 fdput(f);
884 } else {
885 unsigned int lookup_flags = 0;
886
887 if (!(flags & FAN_MARK_DONT_FOLLOW))
888 lookup_flags |= LOOKUP_FOLLOW;
889 if (flags & FAN_MARK_ONLYDIR)
890 lookup_flags |= LOOKUP_DIRECTORY;
891
892 ret = user_path_at(dfd, filename, lookup_flags, path);
893 if (ret)
894 goto out;
895 }
896
897 /* you can only watch an inode if you have read permissions on it */
898 ret = path_permission(path, MAY_READ);
899 if (ret) {
900 path_put(path);
901 goto out;
902 }
903
904 ret = security_path_notify(path, mask, obj_type);
905 if (ret)
906 path_put(path);
907
908 out:
909 return ret;
910 }
911
fanotify_mark_remove_from_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int flags,__u32 umask,int * destroy)912 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
913 __u32 mask, unsigned int flags,
914 __u32 umask, int *destroy)
915 {
916 __u32 oldmask = 0;
917
918 /* umask bits cannot be removed by user */
919 mask &= ~umask;
920 spin_lock(&fsn_mark->lock);
921 if (!(flags & FAN_MARK_IGNORED_MASK)) {
922 oldmask = fsn_mark->mask;
923 fsn_mark->mask &= ~mask;
924 } else {
925 fsn_mark->ignored_mask &= ~mask;
926 }
927 /*
928 * We need to keep the mark around even if remaining mask cannot
929 * result in any events (e.g. mask == FAN_ONDIR) to support incremenal
930 * changes to the mask.
931 * Destroy mark when only umask bits remain.
932 */
933 *destroy = !((fsn_mark->mask | fsn_mark->ignored_mask) & ~umask);
934 spin_unlock(&fsn_mark->lock);
935
936 return mask & oldmask;
937 }
938
fanotify_remove_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,__u32 mask,unsigned int flags,__u32 umask)939 static int fanotify_remove_mark(struct fsnotify_group *group,
940 fsnotify_connp_t *connp, __u32 mask,
941 unsigned int flags, __u32 umask)
942 {
943 struct fsnotify_mark *fsn_mark = NULL;
944 __u32 removed;
945 int destroy_mark;
946
947 mutex_lock(&group->mark_mutex);
948 fsn_mark = fsnotify_find_mark(connp, group);
949 if (!fsn_mark) {
950 mutex_unlock(&group->mark_mutex);
951 return -ENOENT;
952 }
953
954 removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
955 umask, &destroy_mark);
956 if (removed & fsnotify_conn_mask(fsn_mark->connector))
957 fsnotify_recalc_mask(fsn_mark->connector);
958 if (destroy_mark)
959 fsnotify_detach_mark(fsn_mark);
960 mutex_unlock(&group->mark_mutex);
961 if (destroy_mark)
962 fsnotify_free_mark(fsn_mark);
963
964 /* matches the fsnotify_find_mark() */
965 fsnotify_put_mark(fsn_mark);
966 return 0;
967 }
968
fanotify_remove_vfsmount_mark(struct fsnotify_group * group,struct vfsmount * mnt,__u32 mask,unsigned int flags,__u32 umask)969 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
970 struct vfsmount *mnt, __u32 mask,
971 unsigned int flags, __u32 umask)
972 {
973 return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
974 mask, flags, umask);
975 }
976
fanotify_remove_sb_mark(struct fsnotify_group * group,struct super_block * sb,__u32 mask,unsigned int flags,__u32 umask)977 static int fanotify_remove_sb_mark(struct fsnotify_group *group,
978 struct super_block *sb, __u32 mask,
979 unsigned int flags, __u32 umask)
980 {
981 return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask,
982 flags, umask);
983 }
984
fanotify_remove_inode_mark(struct fsnotify_group * group,struct inode * inode,__u32 mask,unsigned int flags,__u32 umask)985 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
986 struct inode *inode, __u32 mask,
987 unsigned int flags, __u32 umask)
988 {
989 return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask,
990 flags, umask);
991 }
992
fanotify_mark_add_to_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int flags)993 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
994 __u32 mask,
995 unsigned int flags)
996 {
997 __u32 oldmask = -1;
998
999 spin_lock(&fsn_mark->lock);
1000 if (!(flags & FAN_MARK_IGNORED_MASK)) {
1001 oldmask = fsn_mark->mask;
1002 fsn_mark->mask |= mask;
1003 } else {
1004 fsn_mark->ignored_mask |= mask;
1005 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
1006 fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
1007 }
1008 spin_unlock(&fsn_mark->lock);
1009
1010 return mask & ~oldmask;
1011 }
1012
fanotify_add_new_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,unsigned int type,__kernel_fsid_t * fsid)1013 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
1014 fsnotify_connp_t *connp,
1015 unsigned int type,
1016 __kernel_fsid_t *fsid)
1017 {
1018 struct ucounts *ucounts = group->fanotify_data.ucounts;
1019 struct fsnotify_mark *mark;
1020 int ret;
1021
1022 /*
1023 * Enforce per user marks limits per user in all containing user ns.
1024 * A group with FAN_UNLIMITED_MARKS does not contribute to mark count
1025 * in the limited groups account.
1026 */
1027 if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS) &&
1028 !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
1029 return ERR_PTR(-ENOSPC);
1030
1031 mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
1032 if (!mark) {
1033 ret = -ENOMEM;
1034 goto out_dec_ucounts;
1035 }
1036
1037 fsnotify_init_mark(mark, group);
1038 ret = fsnotify_add_mark_locked(mark, connp, type, 0, fsid);
1039 if (ret) {
1040 fsnotify_put_mark(mark);
1041 goto out_dec_ucounts;
1042 }
1043
1044 return mark;
1045
1046 out_dec_ucounts:
1047 if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS))
1048 dec_ucount(ucounts, UCOUNT_FANOTIFY_MARKS);
1049 return ERR_PTR(ret);
1050 }
1051
1052
fanotify_add_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,unsigned int type,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1053 static int fanotify_add_mark(struct fsnotify_group *group,
1054 fsnotify_connp_t *connp, unsigned int type,
1055 __u32 mask, unsigned int flags,
1056 __kernel_fsid_t *fsid)
1057 {
1058 struct fsnotify_mark *fsn_mark;
1059 __u32 added;
1060
1061 mutex_lock(&group->mark_mutex);
1062 fsn_mark = fsnotify_find_mark(connp, group);
1063 if (!fsn_mark) {
1064 fsn_mark = fanotify_add_new_mark(group, connp, type, fsid);
1065 if (IS_ERR(fsn_mark)) {
1066 mutex_unlock(&group->mark_mutex);
1067 return PTR_ERR(fsn_mark);
1068 }
1069 }
1070 added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
1071 if (added & ~fsnotify_conn_mask(fsn_mark->connector))
1072 fsnotify_recalc_mask(fsn_mark->connector);
1073 mutex_unlock(&group->mark_mutex);
1074
1075 fsnotify_put_mark(fsn_mark);
1076 return 0;
1077 }
1078
fanotify_add_vfsmount_mark(struct fsnotify_group * group,struct vfsmount * mnt,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1079 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
1080 struct vfsmount *mnt, __u32 mask,
1081 unsigned int flags, __kernel_fsid_t *fsid)
1082 {
1083 return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
1084 FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid);
1085 }
1086
fanotify_add_sb_mark(struct fsnotify_group * group,struct super_block * sb,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1087 static int fanotify_add_sb_mark(struct fsnotify_group *group,
1088 struct super_block *sb, __u32 mask,
1089 unsigned int flags, __kernel_fsid_t *fsid)
1090 {
1091 return fanotify_add_mark(group, &sb->s_fsnotify_marks,
1092 FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid);
1093 }
1094
fanotify_add_inode_mark(struct fsnotify_group * group,struct inode * inode,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1095 static int fanotify_add_inode_mark(struct fsnotify_group *group,
1096 struct inode *inode, __u32 mask,
1097 unsigned int flags, __kernel_fsid_t *fsid)
1098 {
1099 pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
1100
1101 /*
1102 * If some other task has this inode open for write we should not add
1103 * an ignored mark, unless that ignored mark is supposed to survive
1104 * modification changes anyway.
1105 */
1106 if ((flags & FAN_MARK_IGNORED_MASK) &&
1107 !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1108 inode_is_open_for_write(inode))
1109 return 0;
1110
1111 return fanotify_add_mark(group, &inode->i_fsnotify_marks,
1112 FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
1113 }
1114
fanotify_alloc_overflow_event(void)1115 static struct fsnotify_event *fanotify_alloc_overflow_event(void)
1116 {
1117 struct fanotify_event *oevent;
1118
1119 oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
1120 if (!oevent)
1121 return NULL;
1122
1123 fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
1124 oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
1125
1126 return &oevent->fse;
1127 }
1128
fanotify_alloc_merge_hash(void)1129 static struct hlist_head *fanotify_alloc_merge_hash(void)
1130 {
1131 struct hlist_head *hash;
1132
1133 hash = kmalloc(sizeof(struct hlist_head) << FANOTIFY_HTABLE_BITS,
1134 GFP_KERNEL_ACCOUNT);
1135 if (!hash)
1136 return NULL;
1137
1138 __hash_init(hash, FANOTIFY_HTABLE_SIZE);
1139
1140 return hash;
1141 }
1142
1143 /* fanotify syscalls */
SYSCALL_DEFINE2(fanotify_init,unsigned int,flags,unsigned int,event_f_flags)1144 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
1145 {
1146 struct fsnotify_group *group;
1147 int f_flags, fd;
1148 unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
1149 unsigned int class = flags & FANOTIFY_CLASS_BITS;
1150 unsigned int internal_flags = 0;
1151
1152 pr_debug("%s: flags=%x event_f_flags=%x\n",
1153 __func__, flags, event_f_flags);
1154
1155 if (!capable(CAP_SYS_ADMIN)) {
1156 /*
1157 * An unprivileged user can setup an fanotify group with
1158 * limited functionality - an unprivileged group is limited to
1159 * notification events with file handles and it cannot use
1160 * unlimited queue/marks.
1161 */
1162 if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) || !fid_mode)
1163 return -EPERM;
1164
1165 /*
1166 * Setting the internal flag FANOTIFY_UNPRIV on the group
1167 * prevents setting mount/filesystem marks on this group and
1168 * prevents reporting pid and open fd in events.
1169 */
1170 internal_flags |= FANOTIFY_UNPRIV;
1171 }
1172
1173 #ifdef CONFIG_AUDITSYSCALL
1174 if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
1175 #else
1176 if (flags & ~FANOTIFY_INIT_FLAGS)
1177 #endif
1178 return -EINVAL;
1179
1180 /*
1181 * A pidfd can only be returned for a thread-group leader; thus
1182 * FAN_REPORT_PIDFD and FAN_REPORT_TID need to remain mutually
1183 * exclusive.
1184 */
1185 if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
1186 return -EINVAL;
1187
1188 if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
1189 return -EINVAL;
1190
1191 switch (event_f_flags & O_ACCMODE) {
1192 case O_RDONLY:
1193 case O_RDWR:
1194 case O_WRONLY:
1195 break;
1196 default:
1197 return -EINVAL;
1198 }
1199
1200 if (fid_mode && class != FAN_CLASS_NOTIF)
1201 return -EINVAL;
1202
1203 /*
1204 * Child name is reported with parent fid so requires dir fid.
1205 * We can report both child fid and dir fid with or without name.
1206 */
1207 if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
1208 return -EINVAL;
1209
1210 f_flags = O_RDWR | FMODE_NONOTIFY;
1211 if (flags & FAN_CLOEXEC)
1212 f_flags |= O_CLOEXEC;
1213 if (flags & FAN_NONBLOCK)
1214 f_flags |= O_NONBLOCK;
1215
1216 /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
1217 group = fsnotify_alloc_user_group(&fanotify_fsnotify_ops);
1218 if (IS_ERR(group)) {
1219 return PTR_ERR(group);
1220 }
1221
1222 /* Enforce groups limits per user in all containing user ns */
1223 group->fanotify_data.ucounts = inc_ucount(current_user_ns(),
1224 current_euid(),
1225 UCOUNT_FANOTIFY_GROUPS);
1226 if (!group->fanotify_data.ucounts) {
1227 fd = -EMFILE;
1228 goto out_destroy_group;
1229 }
1230
1231 group->fanotify_data.flags = flags | internal_flags;
1232 group->memcg = get_mem_cgroup_from_mm(current->mm);
1233
1234 group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
1235 if (!group->fanotify_data.merge_hash) {
1236 fd = -ENOMEM;
1237 goto out_destroy_group;
1238 }
1239
1240 group->overflow_event = fanotify_alloc_overflow_event();
1241 if (unlikely(!group->overflow_event)) {
1242 fd = -ENOMEM;
1243 goto out_destroy_group;
1244 }
1245
1246 if (force_o_largefile())
1247 event_f_flags |= O_LARGEFILE;
1248 group->fanotify_data.f_flags = event_f_flags;
1249 init_waitqueue_head(&group->fanotify_data.access_waitq);
1250 INIT_LIST_HEAD(&group->fanotify_data.access_list);
1251 switch (class) {
1252 case FAN_CLASS_NOTIF:
1253 group->priority = FS_PRIO_0;
1254 break;
1255 case FAN_CLASS_CONTENT:
1256 group->priority = FS_PRIO_1;
1257 break;
1258 case FAN_CLASS_PRE_CONTENT:
1259 group->priority = FS_PRIO_2;
1260 break;
1261 default:
1262 fd = -EINVAL;
1263 goto out_destroy_group;
1264 }
1265
1266 if (flags & FAN_UNLIMITED_QUEUE) {
1267 fd = -EPERM;
1268 if (!capable(CAP_SYS_ADMIN))
1269 goto out_destroy_group;
1270 group->max_events = UINT_MAX;
1271 } else {
1272 group->max_events = fanotify_max_queued_events;
1273 }
1274
1275 if (flags & FAN_UNLIMITED_MARKS) {
1276 fd = -EPERM;
1277 if (!capable(CAP_SYS_ADMIN))
1278 goto out_destroy_group;
1279 }
1280
1281 if (flags & FAN_ENABLE_AUDIT) {
1282 fd = -EPERM;
1283 if (!capable(CAP_AUDIT_WRITE))
1284 goto out_destroy_group;
1285 }
1286
1287 fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
1288 if (fd < 0)
1289 goto out_destroy_group;
1290
1291 return fd;
1292
1293 out_destroy_group:
1294 fsnotify_destroy_group(group);
1295 return fd;
1296 }
1297
1298 /* Check if filesystem can encode a unique fid */
fanotify_test_fid(struct path * path,__kernel_fsid_t * fsid)1299 static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
1300 {
1301 __kernel_fsid_t root_fsid;
1302 int err;
1303
1304 /*
1305 * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
1306 */
1307 err = vfs_get_fsid(path->dentry, fsid);
1308 if (err)
1309 return err;
1310
1311 if (!fsid->val[0] && !fsid->val[1])
1312 return -ENODEV;
1313
1314 /*
1315 * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
1316 * which uses a different fsid than sb root.
1317 */
1318 err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
1319 if (err)
1320 return err;
1321
1322 if (root_fsid.val[0] != fsid->val[0] ||
1323 root_fsid.val[1] != fsid->val[1])
1324 return -EXDEV;
1325
1326 /*
1327 * We need to make sure that the file system supports at least
1328 * encoding a file handle so user can use name_to_handle_at() to
1329 * compare fid returned with event to the file handle of watched
1330 * objects. However, name_to_handle_at() requires that the
1331 * filesystem also supports decoding file handles.
1332 */
1333 if (!path->dentry->d_sb->s_export_op ||
1334 !path->dentry->d_sb->s_export_op->fh_to_dentry)
1335 return -EOPNOTSUPP;
1336
1337 return 0;
1338 }
1339
fanotify_events_supported(struct path * path,__u64 mask)1340 static int fanotify_events_supported(struct path *path, __u64 mask)
1341 {
1342 /*
1343 * Some filesystems such as 'proc' acquire unusual locks when opening
1344 * files. For them fanotify permission events have high chances of
1345 * deadlocking the system - open done when reporting fanotify event
1346 * blocks on this "unusual" lock while another process holding the lock
1347 * waits for fanotify permission event to be answered. Just disallow
1348 * permission events for such filesystems.
1349 */
1350 if (mask & FANOTIFY_PERM_EVENTS &&
1351 path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
1352 return -EINVAL;
1353 return 0;
1354 }
1355
do_fanotify_mark(int fanotify_fd,unsigned int flags,__u64 mask,int dfd,const char __user * pathname)1356 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
1357 int dfd, const char __user *pathname)
1358 {
1359 struct inode *inode = NULL;
1360 struct vfsmount *mnt = NULL;
1361 struct fsnotify_group *group;
1362 struct fd f;
1363 struct path path;
1364 __kernel_fsid_t __fsid, *fsid = NULL;
1365 u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
1366 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1367 bool ignored = flags & FAN_MARK_IGNORED_MASK;
1368 unsigned int obj_type, fid_mode;
1369 u32 umask = 0;
1370 int ret;
1371
1372 pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
1373 __func__, fanotify_fd, flags, dfd, pathname, mask);
1374
1375 /* we only use the lower 32 bits as of right now. */
1376 if (upper_32_bits(mask))
1377 return -EINVAL;
1378
1379 if (flags & ~FANOTIFY_MARK_FLAGS)
1380 return -EINVAL;
1381
1382 switch (mark_type) {
1383 case FAN_MARK_INODE:
1384 obj_type = FSNOTIFY_OBJ_TYPE_INODE;
1385 break;
1386 case FAN_MARK_MOUNT:
1387 obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
1388 break;
1389 case FAN_MARK_FILESYSTEM:
1390 obj_type = FSNOTIFY_OBJ_TYPE_SB;
1391 break;
1392 default:
1393 return -EINVAL;
1394 }
1395
1396 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
1397 case FAN_MARK_ADD:
1398 case FAN_MARK_REMOVE:
1399 if (!mask)
1400 return -EINVAL;
1401 break;
1402 case FAN_MARK_FLUSH:
1403 if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
1404 return -EINVAL;
1405 break;
1406 default:
1407 return -EINVAL;
1408 }
1409
1410 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1411 valid_mask |= FANOTIFY_PERM_EVENTS;
1412
1413 if (mask & ~valid_mask)
1414 return -EINVAL;
1415
1416 /* Event flags (ONDIR, ON_CHILD) are meaningless in ignored mask */
1417 if (ignored)
1418 mask &= ~FANOTIFY_EVENT_FLAGS;
1419
1420 f = fdget(fanotify_fd);
1421 if (unlikely(!f.file))
1422 return -EBADF;
1423
1424 /* verify that this is indeed an fanotify instance */
1425 ret = -EINVAL;
1426 if (unlikely(f.file->f_op != &fanotify_fops))
1427 goto fput_and_out;
1428 group = f.file->private_data;
1429
1430 /*
1431 * An unprivileged user is not allowed to setup mount nor filesystem
1432 * marks. This also includes setting up such marks by a group that
1433 * was initialized by an unprivileged user.
1434 */
1435 ret = -EPERM;
1436 if ((!capable(CAP_SYS_ADMIN) ||
1437 FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV)) &&
1438 mark_type != FAN_MARK_INODE)
1439 goto fput_and_out;
1440
1441 /*
1442 * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF. These are not
1443 * allowed to set permissions events.
1444 */
1445 ret = -EINVAL;
1446 if (mask & FANOTIFY_PERM_EVENTS &&
1447 group->priority == FS_PRIO_0)
1448 goto fput_and_out;
1449
1450 /*
1451 * Events with data type inode do not carry enough information to report
1452 * event->fd, so we do not allow setting a mask for inode events unless
1453 * group supports reporting fid.
1454 * inode events are not supported on a mount mark, because they do not
1455 * carry enough information (i.e. path) to be filtered by mount point.
1456 */
1457 fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
1458 if (mask & FANOTIFY_INODE_EVENTS &&
1459 (!fid_mode || mark_type == FAN_MARK_MOUNT))
1460 goto fput_and_out;
1461
1462 if (flags & FAN_MARK_FLUSH) {
1463 ret = 0;
1464 if (mark_type == FAN_MARK_MOUNT)
1465 fsnotify_clear_vfsmount_marks_by_group(group);
1466 else if (mark_type == FAN_MARK_FILESYSTEM)
1467 fsnotify_clear_sb_marks_by_group(group);
1468 else
1469 fsnotify_clear_inode_marks_by_group(group);
1470 goto fput_and_out;
1471 }
1472
1473 ret = fanotify_find_path(dfd, pathname, &path, flags,
1474 (mask & ALL_FSNOTIFY_EVENTS), obj_type);
1475 if (ret)
1476 goto fput_and_out;
1477
1478 if (flags & FAN_MARK_ADD) {
1479 ret = fanotify_events_supported(&path, mask);
1480 if (ret)
1481 goto path_put_and_out;
1482 }
1483
1484 if (fid_mode) {
1485 ret = fanotify_test_fid(&path, &__fsid);
1486 if (ret)
1487 goto path_put_and_out;
1488
1489 fsid = &__fsid;
1490 }
1491
1492 /* inode held in place by reference to path; group by fget on fd */
1493 if (mark_type == FAN_MARK_INODE)
1494 inode = path.dentry->d_inode;
1495 else
1496 mnt = path.mnt;
1497
1498 /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
1499 if (mnt || !S_ISDIR(inode->i_mode)) {
1500 mask &= ~FAN_EVENT_ON_CHILD;
1501 umask = FAN_EVENT_ON_CHILD;
1502 /*
1503 * If group needs to report parent fid, register for getting
1504 * events with parent/name info for non-directory.
1505 */
1506 if ((fid_mode & FAN_REPORT_DIR_FID) &&
1507 (flags & FAN_MARK_ADD) && !ignored)
1508 mask |= FAN_EVENT_ON_CHILD;
1509 }
1510
1511 /* create/update an inode mark */
1512 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
1513 case FAN_MARK_ADD:
1514 if (mark_type == FAN_MARK_MOUNT)
1515 ret = fanotify_add_vfsmount_mark(group, mnt, mask,
1516 flags, fsid);
1517 else if (mark_type == FAN_MARK_FILESYSTEM)
1518 ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
1519 flags, fsid);
1520 else
1521 ret = fanotify_add_inode_mark(group, inode, mask,
1522 flags, fsid);
1523 break;
1524 case FAN_MARK_REMOVE:
1525 if (mark_type == FAN_MARK_MOUNT)
1526 ret = fanotify_remove_vfsmount_mark(group, mnt, mask,
1527 flags, umask);
1528 else if (mark_type == FAN_MARK_FILESYSTEM)
1529 ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask,
1530 flags, umask);
1531 else
1532 ret = fanotify_remove_inode_mark(group, inode, mask,
1533 flags, umask);
1534 break;
1535 default:
1536 ret = -EINVAL;
1537 }
1538
1539 path_put_and_out:
1540 path_put(&path);
1541 fput_and_out:
1542 fdput(f);
1543 return ret;
1544 }
1545
1546 #ifndef CONFIG_ARCH_SPLIT_ARG64
SYSCALL_DEFINE5(fanotify_mark,int,fanotify_fd,unsigned int,flags,__u64,mask,int,dfd,const char __user *,pathname)1547 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
1548 __u64, mask, int, dfd,
1549 const char __user *, pathname)
1550 {
1551 return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
1552 }
1553 #endif
1554
1555 #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)1556 SYSCALL32_DEFINE6(fanotify_mark,
1557 int, fanotify_fd, unsigned int, flags,
1558 SC_ARG64(mask), int, dfd,
1559 const char __user *, pathname)
1560 {
1561 return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask),
1562 dfd, pathname);
1563 }
1564 #endif
1565
1566 /*
1567 * fanotify_user_setup - Our initialization function. Note that we cannot return
1568 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
1569 * must result in panic().
1570 */
fanotify_user_setup(void)1571 static int __init fanotify_user_setup(void)
1572 {
1573 struct sysinfo si;
1574 int max_marks;
1575
1576 si_meminfo(&si);
1577 /*
1578 * Allow up to 1% of addressable memory to be accounted for per user
1579 * marks limited to the range [8192, 1048576]. mount and sb marks are
1580 * a lot cheaper than inode marks, but there is no reason for a user
1581 * to have many of those, so calculate by the cost of inode marks.
1582 */
1583 max_marks = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) /
1584 INODE_MARK_COST;
1585 max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
1586 FANOTIFY_DEFAULT_MAX_USER_MARKS);
1587
1588 BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
1589 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 11);
1590 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
1591
1592 fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
1593 SLAB_PANIC|SLAB_ACCOUNT);
1594 fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
1595 SLAB_PANIC);
1596 fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
1597 SLAB_PANIC);
1598 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
1599 fanotify_perm_event_cachep =
1600 KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
1601 }
1602
1603 fanotify_max_queued_events = FANOTIFY_DEFAULT_MAX_EVENTS;
1604 init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS] =
1605 FANOTIFY_DEFAULT_MAX_GROUPS;
1606 init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS] = max_marks;
1607
1608 return 0;
1609 }
1610 device_initcall(fanotify_user_setup);
1611
