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WIP FPC-III support
[linux/fpc-iii.git] / fs / notify / fanotify / fanotify_user.c
blobdcab112e1f0012073456c56b52b1ce4ac261d9a4
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 "../../mount.h"
26 #include "../fdinfo.h"
27 #include "fanotify.h"
28
29 #define FANOTIFY_DEFAULT_MAX_EVENTS 16384
30 #define FANOTIFY_DEFAULT_MAX_MARKS 8192
31 #define FANOTIFY_DEFAULT_MAX_LISTENERS 128
32
33 /*
34 * All flags that may be specified in parameter event_f_flags of fanotify_init.
35 *
36 * Internal and external open flags are stored together in field f_flags of
37 * struct file. Only external open flags shall be allowed in event_f_flags.
38 * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
39 * excluded.
40 */
41 #define FANOTIFY_INIT_ALL_EVENT_F_BITS ( \
42 O_ACCMODE | O_APPEND | O_NONBLOCK | \
43 __O_SYNC | O_DSYNC | O_CLOEXEC | \
44 O_LARGEFILE | O_NOATIME )
45
46 extern const struct fsnotify_ops fanotify_fsnotify_ops;
47
48 struct kmem_cache *fanotify_mark_cache __read_mostly;
49 struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
50 struct kmem_cache *fanotify_path_event_cachep __read_mostly;
51 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
52
53 #define FANOTIFY_EVENT_ALIGN 4
54 #define FANOTIFY_INFO_HDR_LEN \
55 (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
56
57 static int fanotify_fid_info_len(int fh_len, int name_len)
58 {
59 int info_len = fh_len;
60
61 if (name_len)
62 info_len += name_len + 1;
63
64 return roundup(FANOTIFY_INFO_HDR_LEN + info_len, FANOTIFY_EVENT_ALIGN);
65 }
66
67 static int fanotify_event_info_len(unsigned int fid_mode,
68 struct fanotify_event *event)
69 {
70 struct fanotify_info *info = fanotify_event_info(event);
71 int dir_fh_len = fanotify_event_dir_fh_len(event);
72 int fh_len = fanotify_event_object_fh_len(event);
73 int info_len = 0;
74 int dot_len = 0;
75
76 if (dir_fh_len) {
77 info_len += fanotify_fid_info_len(dir_fh_len, info->name_len);
78 } else if ((fid_mode & FAN_REPORT_NAME) && (event->mask & FAN_ONDIR)) {
79 /*
80 * With group flag FAN_REPORT_NAME, if name was not recorded in
81 * event on a directory, we will report the name ".".
82 */
83 dot_len = 1;
84 }
85
86 if (fh_len)
87 info_len += fanotify_fid_info_len(fh_len, dot_len);
88
89 return info_len;
90 }
91
92 /*
93 * Get an fanotify notification event if one exists and is small
94 * enough to fit in "count". Return an error pointer if the count
95 * is not large enough. When permission event is dequeued, its state is
96 * updated accordingly.
97 */
98 static struct fanotify_event *get_one_event(struct fsnotify_group *group,
99 size_t count)
100 {
101 size_t event_size = FAN_EVENT_METADATA_LEN;
102 struct fanotify_event *event = NULL;
103 unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
104
105 pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
106
107 spin_lock(&group->notification_lock);
108 if (fsnotify_notify_queue_is_empty(group))
109 goto out;
110
111 if (fid_mode) {
112 event_size += fanotify_event_info_len(fid_mode,
113 FANOTIFY_E(fsnotify_peek_first_event(group)));
114 }
115
116 if (event_size > count) {
117 event = ERR_PTR(-EINVAL);
118 goto out;
119 }
120 event = FANOTIFY_E(fsnotify_remove_first_event(group));
121 if (fanotify_is_perm_event(event->mask))
122 FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
123 out:
124 spin_unlock(&group->notification_lock);
125 return event;
126 }
127
128 static int create_fd(struct fsnotify_group *group, struct path *path,
129 struct file **file)
130 {
131 int client_fd;
132 struct file *new_file;
133
134 client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
135 if (client_fd < 0)
136 return client_fd;
137
138 /*
139 * we need a new file handle for the userspace program so it can read even if it was
140 * originally opened O_WRONLY.
141 */
142 new_file = dentry_open(path,
143 group->fanotify_data.f_flags | FMODE_NONOTIFY,
144 current_cred());
145 if (IS_ERR(new_file)) {
146 /*
147 * we still send an event even if we can't open the file. this
148 * can happen when say tasks are gone and we try to open their
149 * /proc files or we try to open a WRONLY file like in sysfs
150 * we just send the errno to userspace since there isn't much
151 * else we can do.
152 */
153 put_unused_fd(client_fd);
154 client_fd = PTR_ERR(new_file);
155 } else {
156 *file = new_file;
157 }
158
159 return client_fd;
160 }
161
162 /*
163 * Finish processing of permission event by setting it to ANSWERED state and
164 * drop group->notification_lock.
165 */
166 static void finish_permission_event(struct fsnotify_group *group,
167 struct fanotify_perm_event *event,
168 unsigned int response)
169 __releases(&group->notification_lock)
170 {
171 bool destroy = false;
172
173 assert_spin_locked(&group->notification_lock);
174 event->response = response;
175 if (event->state == FAN_EVENT_CANCELED)
176 destroy = true;
177 else
178 event->state = FAN_EVENT_ANSWERED;
179 spin_unlock(&group->notification_lock);
180 if (destroy)
181 fsnotify_destroy_event(group, &event->fae.fse);
182 }
183
184 static int process_access_response(struct fsnotify_group *group,
185 struct fanotify_response *response_struct)
186 {
187 struct fanotify_perm_event *event;
188 int fd = response_struct->fd;
189 int response = response_struct->response;
190
191 pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
192 fd, response);
193 /*
194 * make sure the response is valid, if invalid we do nothing and either
195 * userspace can send a valid response or we will clean it up after the
196 * timeout
197 */
198 switch (response & ~FAN_AUDIT) {
199 case FAN_ALLOW:
200 case FAN_DENY:
201 break;
202 default:
203 return -EINVAL;
204 }
205
206 if (fd < 0)
207 return -EINVAL;
208
209 if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
210 return -EINVAL;
211
212 spin_lock(&group->notification_lock);
213 list_for_each_entry(event, &group->fanotify_data.access_list,
214 fae.fse.list) {
215 if (event->fd != fd)
216 continue;
217
218 list_del_init(&event->fae.fse.list);
219 finish_permission_event(group, event, response);
220 wake_up(&group->fanotify_data.access_waitq);
221 return 0;
222 }
223 spin_unlock(&group->notification_lock);
224
225 return -ENOENT;
226 }
227
228 static int copy_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
229 int info_type, const char *name, size_t name_len,
230 char __user *buf, size_t count)
231 {
232 struct fanotify_event_info_fid info = { };
233 struct file_handle handle = { };
234 unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf;
235 size_t fh_len = fh ? fh->len : 0;
236 size_t info_len = fanotify_fid_info_len(fh_len, name_len);
237 size_t len = info_len;
238
239 pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
240 __func__, fh_len, name_len, info_len, count);
241
242 if (!fh_len)
243 return 0;
244
245 if (WARN_ON_ONCE(len < sizeof(info) || len > count))
246 return -EFAULT;
247
248 /*
249 * Copy event info fid header followed by variable sized file handle
250 * and optionally followed by variable sized filename.
251 */
252 switch (info_type) {
253 case FAN_EVENT_INFO_TYPE_FID:
254 case FAN_EVENT_INFO_TYPE_DFID:
255 if (WARN_ON_ONCE(name_len))
256 return -EFAULT;
257 break;
258 case FAN_EVENT_INFO_TYPE_DFID_NAME:
259 if (WARN_ON_ONCE(!name || !name_len))
260 return -EFAULT;
261 break;
262 default:
263 return -EFAULT;
264 }
265
266 info.hdr.info_type = info_type;
267 info.hdr.len = len;
268 info.fsid = *fsid;
269 if (copy_to_user(buf, &info, sizeof(info)))
270 return -EFAULT;
271
272 buf += sizeof(info);
273 len -= sizeof(info);
274 if (WARN_ON_ONCE(len < sizeof(handle)))
275 return -EFAULT;
276
277 handle.handle_type = fh->type;
278 handle.handle_bytes = fh_len;
279 if (copy_to_user(buf, &handle, sizeof(handle)))
280 return -EFAULT;
281
282 buf += sizeof(handle);
283 len -= sizeof(handle);
284 if (WARN_ON_ONCE(len < fh_len))
285 return -EFAULT;
286
287 /*
288 * For an inline fh and inline file name, copy through stack to exclude
289 * the copy from usercopy hardening protections.
290 */
291 fh_buf = fanotify_fh_buf(fh);
292 if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
293 memcpy(bounce, fh_buf, fh_len);
294 fh_buf = bounce;
295 }
296 if (copy_to_user(buf, fh_buf, fh_len))
297 return -EFAULT;
298
299 buf += fh_len;
300 len -= fh_len;
301
302 if (name_len) {
303 /* Copy the filename with terminating null */
304 name_len++;
305 if (WARN_ON_ONCE(len < name_len))
306 return -EFAULT;
307
308 if (copy_to_user(buf, name, name_len))
309 return -EFAULT;
310
311 buf += name_len;
312 len -= name_len;
313 }
314
315 /* Pad with 0's */
316 WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
317 if (len > 0 && clear_user(buf, len))
318 return -EFAULT;
319
320 return info_len;
321 }
322
323 static ssize_t copy_event_to_user(struct fsnotify_group *group,
324 struct fanotify_event *event,
325 char __user *buf, size_t count)
326 {
327 struct fanotify_event_metadata metadata;
328 struct path *path = fanotify_event_path(event);
329 struct fanotify_info *info = fanotify_event_info(event);
330 unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
331 struct file *f = NULL;
332 int ret, fd = FAN_NOFD;
333 int info_type = 0;
334
335 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
336
337 metadata.event_len = FAN_EVENT_METADATA_LEN +
338 fanotify_event_info_len(fid_mode, event);
339 metadata.metadata_len = FAN_EVENT_METADATA_LEN;
340 metadata.vers = FANOTIFY_METADATA_VERSION;
341 metadata.reserved = 0;
342 metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
343 metadata.pid = pid_vnr(event->pid);
344
345 if (path && path->mnt && path->dentry) {
346 fd = create_fd(group, path, &f);
347 if (fd < 0)
348 return fd;
349 }
350 metadata.fd = fd;
351
352 ret = -EFAULT;
353 /*
354 * Sanity check copy size in case get_one_event() and
355 * event_len sizes ever get out of sync.
356 */
357 if (WARN_ON_ONCE(metadata.event_len > count))
358 goto out_close_fd;
359
360 if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
361 goto out_close_fd;
362
363 buf += FAN_EVENT_METADATA_LEN;
364 count -= FAN_EVENT_METADATA_LEN;
365
366 if (fanotify_is_perm_event(event->mask))
367 FANOTIFY_PERM(event)->fd = fd;
368
369 if (f)
370 fd_install(fd, f);
371
372 /* Event info records order is: dir fid + name, child fid */
373 if (fanotify_event_dir_fh_len(event)) {
374 info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
375 FAN_EVENT_INFO_TYPE_DFID;
376 ret = copy_info_to_user(fanotify_event_fsid(event),
377 fanotify_info_dir_fh(info),
378 info_type, fanotify_info_name(info),
379 info->name_len, buf, count);
380 if (ret < 0)
381 return ret;
382
383 buf += ret;
384 count -= ret;
385 }
386
387 if (fanotify_event_object_fh_len(event)) {
388 const char *dot = NULL;
389 int dot_len = 0;
390
391 if (fid_mode == FAN_REPORT_FID || info_type) {
392 /*
393 * With only group flag FAN_REPORT_FID only type FID is
394 * reported. Second info record type is always FID.
395 */
396 info_type = FAN_EVENT_INFO_TYPE_FID;
397 } else if ((fid_mode & FAN_REPORT_NAME) &&
398 (event->mask & FAN_ONDIR)) {
399 /*
400 * With group flag FAN_REPORT_NAME, if name was not
401 * recorded in an event on a directory, report the
402 * name "." with info type DFID_NAME.
403 */
404 info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
405 dot = ".";
406 dot_len = 1;
407 } else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
408 (event->mask & FAN_ONDIR)) {
409 /*
410 * With group flag FAN_REPORT_DIR_FID, a single info
411 * record has type DFID for directory entry modification
412 * event and for event on a directory.
413 */
414 info_type = FAN_EVENT_INFO_TYPE_DFID;
415 } else {
416 /*
417 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,
418 * a single info record has type FID for event on a
419 * non-directory, when there is no directory to report.
420 * For example, on FAN_DELETE_SELF event.
421 */
422 info_type = FAN_EVENT_INFO_TYPE_FID;
423 }
424
425 ret = copy_info_to_user(fanotify_event_fsid(event),
426 fanotify_event_object_fh(event),
427 info_type, dot, dot_len, buf, count);
428 if (ret < 0)
429 return ret;
430
431 buf += ret;
432 count -= ret;
433 }
434
435 return metadata.event_len;
436
437 out_close_fd:
438 if (fd != FAN_NOFD) {
439 put_unused_fd(fd);
440 fput(f);
441 }
442 return ret;
443 }
444
445 /* intofiy userspace file descriptor functions */
446 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
447 {
448 struct fsnotify_group *group = file->private_data;
449 __poll_t ret = 0;
450
451 poll_wait(file, &group->notification_waitq, wait);
452 spin_lock(&group->notification_lock);
453 if (!fsnotify_notify_queue_is_empty(group))
454 ret = EPOLLIN | EPOLLRDNORM;
455 spin_unlock(&group->notification_lock);
456
457 return ret;
458 }
459
460 static ssize_t fanotify_read(struct file *file, char __user *buf,
461 size_t count, loff_t *pos)
462 {
463 struct fsnotify_group *group;
464 struct fanotify_event *event;
465 char __user *start;
466 int ret;
467 DEFINE_WAIT_FUNC(wait, woken_wake_function);
468
469 start = buf;
470 group = file->private_data;
471
472 pr_debug("%s: group=%p\n", __func__, group);
473
474 add_wait_queue(&group->notification_waitq, &wait);
475 while (1) {
476 /*
477 * User can supply arbitrarily large buffer. Avoid softlockups
478 * in case there are lots of available events.
479 */
480 cond_resched();
481 event = get_one_event(group, count);
482 if (IS_ERR(event)) {
483 ret = PTR_ERR(event);
484 break;
485 }
486
487 if (!event) {
488 ret = -EAGAIN;
489 if (file->f_flags & O_NONBLOCK)
490 break;
491
492 ret = -ERESTARTSYS;
493 if (signal_pending(current))
494 break;
495
496 if (start != buf)
497 break;
498
499 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
500 continue;
501 }
502
503 ret = copy_event_to_user(group, event, buf, count);
504 if (unlikely(ret == -EOPENSTALE)) {
505 /*
506 * We cannot report events with stale fd so drop it.
507 * Setting ret to 0 will continue the event loop and
508 * do the right thing if there are no more events to
509 * read (i.e. return bytes read, -EAGAIN or wait).
510 */
511 ret = 0;
512 }
513
514 /*
515 * Permission events get queued to wait for response. Other
516 * events can be destroyed now.
517 */
518 if (!fanotify_is_perm_event(event->mask)) {
519 fsnotify_destroy_event(group, &event->fse);
520 } else {
521 if (ret <= 0) {
522 spin_lock(&group->notification_lock);
523 finish_permission_event(group,
524 FANOTIFY_PERM(event), FAN_DENY);
525 wake_up(&group->fanotify_data.access_waitq);
526 } else {
527 spin_lock(&group->notification_lock);
528 list_add_tail(&event->fse.list,
529 &group->fanotify_data.access_list);
530 spin_unlock(&group->notification_lock);
531 }
532 }
533 if (ret < 0)
534 break;
535 buf += ret;
536 count -= ret;
537 }
538 remove_wait_queue(&group->notification_waitq, &wait);
539
540 if (start != buf && ret != -EFAULT)
541 ret = buf - start;
542 return ret;
543 }
544
545 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
546 {
547 struct fanotify_response response = { .fd = -1, .response = -1 };
548 struct fsnotify_group *group;
549 int ret;
550
551 if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
552 return -EINVAL;
553
554 group = file->private_data;
555
556 if (count < sizeof(response))
557 return -EINVAL;
558
559 count = sizeof(response);
560
561 pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
562
563 if (copy_from_user(&response, buf, count))
564 return -EFAULT;
565
566 ret = process_access_response(group, &response);
567 if (ret < 0)
568 count = ret;
569
570 return count;
571 }
572
573 static int fanotify_release(struct inode *ignored, struct file *file)
574 {
575 struct fsnotify_group *group = file->private_data;
576
577 /*
578 * Stop new events from arriving in the notification queue. since
579 * userspace cannot use fanotify fd anymore, no event can enter or
580 * leave access_list by now either.
581 */
582 fsnotify_group_stop_queueing(group);
583
584 /*
585 * Process all permission events on access_list and notification queue
586 * and simulate reply from userspace.
587 */
588 spin_lock(&group->notification_lock);
589 while (!list_empty(&group->fanotify_data.access_list)) {
590 struct fanotify_perm_event *event;
591
592 event = list_first_entry(&group->fanotify_data.access_list,
593 struct fanotify_perm_event, fae.fse.list);
594 list_del_init(&event->fae.fse.list);
595 finish_permission_event(group, event, FAN_ALLOW);
596 spin_lock(&group->notification_lock);
597 }
598
599 /*
600 * Destroy all non-permission events. For permission events just
601 * dequeue them and set the response. They will be freed once the
602 * response is consumed and fanotify_get_response() returns.
603 */
604 while (!fsnotify_notify_queue_is_empty(group)) {
605 struct fanotify_event *event;
606
607 event = FANOTIFY_E(fsnotify_remove_first_event(group));
608 if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
609 spin_unlock(&group->notification_lock);
610 fsnotify_destroy_event(group, &event->fse);
611 } else {
612 finish_permission_event(group, FANOTIFY_PERM(event),
613 FAN_ALLOW);
614 }
615 spin_lock(&group->notification_lock);
616 }
617 spin_unlock(&group->notification_lock);
618
619 /* Response for all permission events it set, wakeup waiters */
620 wake_up(&group->fanotify_data.access_waitq);
621
622 /* matches the fanotify_init->fsnotify_alloc_group */
623 fsnotify_destroy_group(group);
624
625 return 0;
626 }
627
628 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
629 {
630 struct fsnotify_group *group;
631 struct fsnotify_event *fsn_event;
632 void __user *p;
633 int ret = -ENOTTY;
634 size_t send_len = 0;
635
636 group = file->private_data;
637
638 p = (void __user *) arg;
639
640 switch (cmd) {
641 case FIONREAD:
642 spin_lock(&group->notification_lock);
643 list_for_each_entry(fsn_event, &group->notification_list, list)
644 send_len += FAN_EVENT_METADATA_LEN;
645 spin_unlock(&group->notification_lock);
646 ret = put_user(send_len, (int __user *) p);
647 break;
648 }
649
650 return ret;
651 }
652
653 static const struct file_operations fanotify_fops = {
654 .show_fdinfo = fanotify_show_fdinfo,
655 .poll = fanotify_poll,
656 .read = fanotify_read,
657 .write = fanotify_write,
658 .fasync = NULL,
659 .release = fanotify_release,
660 .unlocked_ioctl = fanotify_ioctl,
661 .compat_ioctl = compat_ptr_ioctl,
662 .llseek = noop_llseek,
663 };
664
665 static int fanotify_find_path(int dfd, const char __user *filename,
666 struct path *path, unsigned int flags, __u64 mask,
667 unsigned int obj_type)
668 {
669 int ret;
670
671 pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
672 dfd, filename, flags);
673
674 if (filename == NULL) {
675 struct fd f = fdget(dfd);
676
677 ret = -EBADF;
678 if (!f.file)
679 goto out;
680
681 ret = -ENOTDIR;
682 if ((flags & FAN_MARK_ONLYDIR) &&
683 !(S_ISDIR(file_inode(f.file)->i_mode))) {
684 fdput(f);
685 goto out;
686 }
687
688 *path = f.file->f_path;
689 path_get(path);
690 fdput(f);
691 } else {
692 unsigned int lookup_flags = 0;
693
694 if (!(flags & FAN_MARK_DONT_FOLLOW))
695 lookup_flags |= LOOKUP_FOLLOW;
696 if (flags & FAN_MARK_ONLYDIR)
697 lookup_flags |= LOOKUP_DIRECTORY;
698
699 ret = user_path_at(dfd, filename, lookup_flags, path);
700 if (ret)
701 goto out;
702 }
703
704 /* you can only watch an inode if you have read permissions on it */
705 ret = inode_permission(path->dentry->d_inode, MAY_READ);
706 if (ret) {
707 path_put(path);
708 goto out;
709 }
710
711 ret = security_path_notify(path, mask, obj_type);
712 if (ret)
713 path_put(path);
714
715 out:
716 return ret;
717 }
718
719 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
720 __u32 mask, unsigned int flags,
721 __u32 umask, int *destroy)
722 {
723 __u32 oldmask = 0;
724
725 /* umask bits cannot be removed by user */
726 mask &= ~umask;
727 spin_lock(&fsn_mark->lock);
728 if (!(flags & FAN_MARK_IGNORED_MASK)) {
729 oldmask = fsn_mark->mask;
730 fsn_mark->mask &= ~mask;
731 } else {
732 fsn_mark->ignored_mask &= ~mask;
733 }
734 /*
735 * We need to keep the mark around even if remaining mask cannot
736 * result in any events (e.g. mask == FAN_ONDIR) to support incremenal
737 * changes to the mask.
738 * Destroy mark when only umask bits remain.
739 */
740 *destroy = !((fsn_mark->mask | fsn_mark->ignored_mask) & ~umask);
741 spin_unlock(&fsn_mark->lock);
742
743 return mask & oldmask;
744 }
745
746 static int fanotify_remove_mark(struct fsnotify_group *group,
747 fsnotify_connp_t *connp, __u32 mask,
748 unsigned int flags, __u32 umask)
749 {
750 struct fsnotify_mark *fsn_mark = NULL;
751 __u32 removed;
752 int destroy_mark;
753
754 mutex_lock(&group->mark_mutex);
755 fsn_mark = fsnotify_find_mark(connp, group);
756 if (!fsn_mark) {
757 mutex_unlock(&group->mark_mutex);
758 return -ENOENT;
759 }
760
761 removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
762 umask, &destroy_mark);
763 if (removed & fsnotify_conn_mask(fsn_mark->connector))
764 fsnotify_recalc_mask(fsn_mark->connector);
765 if (destroy_mark)
766 fsnotify_detach_mark(fsn_mark);
767 mutex_unlock(&group->mark_mutex);
768 if (destroy_mark)
769 fsnotify_free_mark(fsn_mark);
770
771 /* matches the fsnotify_find_mark() */
772 fsnotify_put_mark(fsn_mark);
773 return 0;
774 }
775
776 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
777 struct vfsmount *mnt, __u32 mask,
778 unsigned int flags, __u32 umask)
779 {
780 return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
781 mask, flags, umask);
782 }
783
784 static int fanotify_remove_sb_mark(struct fsnotify_group *group,
785 struct super_block *sb, __u32 mask,
786 unsigned int flags, __u32 umask)
787 {
788 return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask,
789 flags, umask);
790 }
791
792 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
793 struct inode *inode, __u32 mask,
794 unsigned int flags, __u32 umask)
795 {
796 return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask,
797 flags, umask);
798 }
799
800 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
801 __u32 mask,
802 unsigned int flags)
803 {
804 __u32 oldmask = -1;
805
806 spin_lock(&fsn_mark->lock);
807 if (!(flags & FAN_MARK_IGNORED_MASK)) {
808 oldmask = fsn_mark->mask;
809 fsn_mark->mask |= mask;
810 } else {
811 fsn_mark->ignored_mask |= mask;
812 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
813 fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
814 }
815 spin_unlock(&fsn_mark->lock);
816
817 return mask & ~oldmask;
818 }
819
820 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
821 fsnotify_connp_t *connp,
822 unsigned int type,
823 __kernel_fsid_t *fsid)
824 {
825 struct fsnotify_mark *mark;
826 int ret;
827
828 if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
829 return ERR_PTR(-ENOSPC);
830
831 mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
832 if (!mark)
833 return ERR_PTR(-ENOMEM);
834
835 fsnotify_init_mark(mark, group);
836 ret = fsnotify_add_mark_locked(mark, connp, type, 0, fsid);
837 if (ret) {
838 fsnotify_put_mark(mark);
839 return ERR_PTR(ret);
840 }
841
842 return mark;
843 }
844
845
846 static int fanotify_add_mark(struct fsnotify_group *group,
847 fsnotify_connp_t *connp, unsigned int type,
848 __u32 mask, unsigned int flags,
849 __kernel_fsid_t *fsid)
850 {
851 struct fsnotify_mark *fsn_mark;
852 __u32 added;
853
854 mutex_lock(&group->mark_mutex);
855 fsn_mark = fsnotify_find_mark(connp, group);
856 if (!fsn_mark) {
857 fsn_mark = fanotify_add_new_mark(group, connp, type, fsid);
858 if (IS_ERR(fsn_mark)) {
859 mutex_unlock(&group->mark_mutex);
860 return PTR_ERR(fsn_mark);
861 }
862 }
863 added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
864 if (added & ~fsnotify_conn_mask(fsn_mark->connector))
865 fsnotify_recalc_mask(fsn_mark->connector);
866 mutex_unlock(&group->mark_mutex);
867
868 fsnotify_put_mark(fsn_mark);
869 return 0;
870 }
871
872 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
873 struct vfsmount *mnt, __u32 mask,
874 unsigned int flags, __kernel_fsid_t *fsid)
875 {
876 return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
877 FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid);
878 }
879
880 static int fanotify_add_sb_mark(struct fsnotify_group *group,
881 struct super_block *sb, __u32 mask,
882 unsigned int flags, __kernel_fsid_t *fsid)
883 {
884 return fanotify_add_mark(group, &sb->s_fsnotify_marks,
885 FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid);
886 }
887
888 static int fanotify_add_inode_mark(struct fsnotify_group *group,
889 struct inode *inode, __u32 mask,
890 unsigned int flags, __kernel_fsid_t *fsid)
891 {
892 pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
893
894 /*
895 * If some other task has this inode open for write we should not add
896 * an ignored mark, unless that ignored mark is supposed to survive
897 * modification changes anyway.
898 */
899 if ((flags & FAN_MARK_IGNORED_MASK) &&
900 !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
901 inode_is_open_for_write(inode))
902 return 0;
903
904 return fanotify_add_mark(group, &inode->i_fsnotify_marks,
905 FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
906 }
907
908 static struct fsnotify_event *fanotify_alloc_overflow_event(void)
909 {
910 struct fanotify_event *oevent;
911
912 oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
913 if (!oevent)
914 return NULL;
915
916 fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
917 oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
918
919 return &oevent->fse;
920 }
921
922 /* fanotify syscalls */
923 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
924 {
925 struct fsnotify_group *group;
926 int f_flags, fd;
927 struct user_struct *user;
928 unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
929 unsigned int class = flags & FANOTIFY_CLASS_BITS;
930
931 pr_debug("%s: flags=%x event_f_flags=%x\n",
932 __func__, flags, event_f_flags);
933
934 if (!capable(CAP_SYS_ADMIN))
935 return -EPERM;
936
937 #ifdef CONFIG_AUDITSYSCALL
938 if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
939 #else
940 if (flags & ~FANOTIFY_INIT_FLAGS)
941 #endif
942 return -EINVAL;
943
944 if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
945 return -EINVAL;
946
947 switch (event_f_flags & O_ACCMODE) {
948 case O_RDONLY:
949 case O_RDWR:
950 case O_WRONLY:
951 break;
952 default:
953 return -EINVAL;
954 }
955
956 if (fid_mode && class != FAN_CLASS_NOTIF)
957 return -EINVAL;
958
959 /*
960 * Child name is reported with parent fid so requires dir fid.
961 * We can report both child fid and dir fid with or without name.
962 */
963 if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
964 return -EINVAL;
965
966 user = get_current_user();
967 if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
968 free_uid(user);
969 return -EMFILE;
970 }
971
972 f_flags = O_RDWR | FMODE_NONOTIFY;
973 if (flags & FAN_CLOEXEC)
974 f_flags |= O_CLOEXEC;
975 if (flags & FAN_NONBLOCK)
976 f_flags |= O_NONBLOCK;
977
978 /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
979 group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
980 if (IS_ERR(group)) {
981 free_uid(user);
982 return PTR_ERR(group);
983 }
984
985 group->fanotify_data.user = user;
986 group->fanotify_data.flags = flags;
987 atomic_inc(&user->fanotify_listeners);
988 group->memcg = get_mem_cgroup_from_mm(current->mm);
989
990 group->overflow_event = fanotify_alloc_overflow_event();
991 if (unlikely(!group->overflow_event)) {
992 fd = -ENOMEM;
993 goto out_destroy_group;
994 }
995
996 if (force_o_largefile())
997 event_f_flags |= O_LARGEFILE;
998 group->fanotify_data.f_flags = event_f_flags;
999 init_waitqueue_head(&group->fanotify_data.access_waitq);
1000 INIT_LIST_HEAD(&group->fanotify_data.access_list);
1001 switch (class) {
1002 case FAN_CLASS_NOTIF:
1003 group->priority = FS_PRIO_0;
1004 break;
1005 case FAN_CLASS_CONTENT:
1006 group->priority = FS_PRIO_1;
1007 break;
1008 case FAN_CLASS_PRE_CONTENT:
1009 group->priority = FS_PRIO_2;
1010 break;
1011 default:
1012 fd = -EINVAL;
1013 goto out_destroy_group;
1014 }
1015
1016 if (flags & FAN_UNLIMITED_QUEUE) {
1017 fd = -EPERM;
1018 if (!capable(CAP_SYS_ADMIN))
1019 goto out_destroy_group;
1020 group->max_events = UINT_MAX;
1021 } else {
1022 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
1023 }
1024
1025 if (flags & FAN_UNLIMITED_MARKS) {
1026 fd = -EPERM;
1027 if (!capable(CAP_SYS_ADMIN))
1028 goto out_destroy_group;
1029 group->fanotify_data.max_marks = UINT_MAX;
1030 } else {
1031 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
1032 }
1033
1034 if (flags & FAN_ENABLE_AUDIT) {
1035 fd = -EPERM;
1036 if (!capable(CAP_AUDIT_WRITE))
1037 goto out_destroy_group;
1038 }
1039
1040 fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
1041 if (fd < 0)
1042 goto out_destroy_group;
1043
1044 return fd;
1045
1046 out_destroy_group:
1047 fsnotify_destroy_group(group);
1048 return fd;
1049 }
1050
1051 /* Check if filesystem can encode a unique fid */
1052 static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
1053 {
1054 __kernel_fsid_t root_fsid;
1055 int err;
1056
1057 /*
1058 * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
1059 */
1060 err = vfs_get_fsid(path->dentry, fsid);
1061 if (err)
1062 return err;
1063
1064 if (!fsid->val[0] && !fsid->val[1])
1065 return -ENODEV;
1066
1067 /*
1068 * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
1069 * which uses a different fsid than sb root.
1070 */
1071 err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
1072 if (err)
1073 return err;
1074
1075 if (root_fsid.val[0] != fsid->val[0] ||
1076 root_fsid.val[1] != fsid->val[1])
1077 return -EXDEV;
1078
1079 /*
1080 * We need to make sure that the file system supports at least
1081 * encoding a file handle so user can use name_to_handle_at() to
1082 * compare fid returned with event to the file handle of watched
1083 * objects. However, name_to_handle_at() requires that the
1084 * filesystem also supports decoding file handles.
1085 */
1086 if (!path->dentry->d_sb->s_export_op ||
1087 !path->dentry->d_sb->s_export_op->fh_to_dentry)
1088 return -EOPNOTSUPP;
1089
1090 return 0;
1091 }
1092
1093 static int fanotify_events_supported(struct path *path, __u64 mask)
1094 {
1095 /*
1096 * Some filesystems such as 'proc' acquire unusual locks when opening
1097 * files. For them fanotify permission events have high chances of
1098 * deadlocking the system - open done when reporting fanotify event
1099 * blocks on this "unusual" lock while another process holding the lock
1100 * waits for fanotify permission event to be answered. Just disallow
1101 * permission events for such filesystems.
1102 */
1103 if (mask & FANOTIFY_PERM_EVENTS &&
1104 path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
1105 return -EINVAL;
1106 return 0;
1107 }
1108
1109 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
1110 int dfd, const char __user *pathname)
1111 {
1112 struct inode *inode = NULL;
1113 struct vfsmount *mnt = NULL;
1114 struct fsnotify_group *group;
1115 struct fd f;
1116 struct path path;
1117 __kernel_fsid_t __fsid, *fsid = NULL;
1118 u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
1119 unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1120 bool ignored = flags & FAN_MARK_IGNORED_MASK;
1121 unsigned int obj_type, fid_mode;
1122 u32 umask = 0;
1123 int ret;
1124
1125 pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
1126 __func__, fanotify_fd, flags, dfd, pathname, mask);
1127
1128 /* we only use the lower 32 bits as of right now. */
1129 if (mask & ((__u64)0xffffffff << 32))
1130 return -EINVAL;
1131
1132 if (flags & ~FANOTIFY_MARK_FLAGS)
1133 return -EINVAL;
1134
1135 switch (mark_type) {
1136 case FAN_MARK_INODE:
1137 obj_type = FSNOTIFY_OBJ_TYPE_INODE;
1138 break;
1139 case FAN_MARK_MOUNT:
1140 obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
1141 break;
1142 case FAN_MARK_FILESYSTEM:
1143 obj_type = FSNOTIFY_OBJ_TYPE_SB;
1144 break;
1145 default:
1146 return -EINVAL;
1147 }
1148
1149 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
1150 case FAN_MARK_ADD:
1151 case FAN_MARK_REMOVE:
1152 if (!mask)
1153 return -EINVAL;
1154 break;
1155 case FAN_MARK_FLUSH:
1156 if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
1157 return -EINVAL;
1158 break;
1159 default:
1160 return -EINVAL;
1161 }
1162
1163 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1164 valid_mask |= FANOTIFY_PERM_EVENTS;
1165
1166 if (mask & ~valid_mask)
1167 return -EINVAL;
1168
1169 /* Event flags (ONDIR, ON_CHILD) are meaningless in ignored mask */
1170 if (ignored)
1171 mask &= ~FANOTIFY_EVENT_FLAGS;
1172
1173 f = fdget(fanotify_fd);
1174 if (unlikely(!f.file))
1175 return -EBADF;
1176
1177 /* verify that this is indeed an fanotify instance */
1178 ret = -EINVAL;
1179 if (unlikely(f.file->f_op != &fanotify_fops))
1180 goto fput_and_out;
1181 group = f.file->private_data;
1182
1183 /*
1184 * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF. These are not
1185 * allowed to set permissions events.
1186 */
1187 ret = -EINVAL;
1188 if (mask & FANOTIFY_PERM_EVENTS &&
1189 group->priority == FS_PRIO_0)
1190 goto fput_and_out;
1191
1192 /*
1193 * Events with data type inode do not carry enough information to report
1194 * event->fd, so we do not allow setting a mask for inode events unless
1195 * group supports reporting fid.
1196 * inode events are not supported on a mount mark, because they do not
1197 * carry enough information (i.e. path) to be filtered by mount point.
1198 */
1199 fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
1200 if (mask & FANOTIFY_INODE_EVENTS &&
1201 (!fid_mode || mark_type == FAN_MARK_MOUNT))
1202 goto fput_and_out;
1203
1204 if (flags & FAN_MARK_FLUSH) {
1205 ret = 0;
1206 if (mark_type == FAN_MARK_MOUNT)
1207 fsnotify_clear_vfsmount_marks_by_group(group);
1208 else if (mark_type == FAN_MARK_FILESYSTEM)
1209 fsnotify_clear_sb_marks_by_group(group);
1210 else
1211 fsnotify_clear_inode_marks_by_group(group);
1212 goto fput_and_out;
1213 }
1214
1215 ret = fanotify_find_path(dfd, pathname, &path, flags,
1216 (mask & ALL_FSNOTIFY_EVENTS), obj_type);
1217 if (ret)
1218 goto fput_and_out;
1219
1220 if (flags & FAN_MARK_ADD) {
1221 ret = fanotify_events_supported(&path, mask);
1222 if (ret)
1223 goto path_put_and_out;
1224 }
1225
1226 if (fid_mode) {
1227 ret = fanotify_test_fid(&path, &__fsid);
1228 if (ret)
1229 goto path_put_and_out;
1230
1231 fsid = &__fsid;
1232 }
1233
1234 /* inode held in place by reference to path; group by fget on fd */
1235 if (mark_type == FAN_MARK_INODE)
1236 inode = path.dentry->d_inode;
1237 else
1238 mnt = path.mnt;
1239
1240 /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
1241 if (mnt || !S_ISDIR(inode->i_mode)) {
1242 mask &= ~FAN_EVENT_ON_CHILD;
1243 umask = FAN_EVENT_ON_CHILD;
1244 /*
1245 * If group needs to report parent fid, register for getting
1246 * events with parent/name info for non-directory.
1247 */
1248 if ((fid_mode & FAN_REPORT_DIR_FID) &&
1249 (flags & FAN_MARK_ADD) && !ignored)
1250 mask |= FAN_EVENT_ON_CHILD;
1251 }
1252
1253 /* create/update an inode mark */
1254 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
1255 case FAN_MARK_ADD:
1256 if (mark_type == FAN_MARK_MOUNT)
1257 ret = fanotify_add_vfsmount_mark(group, mnt, mask,
1258 flags, fsid);
1259 else if (mark_type == FAN_MARK_FILESYSTEM)
1260 ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
1261 flags, fsid);
1262 else
1263 ret = fanotify_add_inode_mark(group, inode, mask,
1264 flags, fsid);
1265 break;
1266 case FAN_MARK_REMOVE:
1267 if (mark_type == FAN_MARK_MOUNT)
1268 ret = fanotify_remove_vfsmount_mark(group, mnt, mask,
1269 flags, umask);
1270 else if (mark_type == FAN_MARK_FILESYSTEM)
1271 ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask,
1272 flags, umask);
1273 else
1274 ret = fanotify_remove_inode_mark(group, inode, mask,
1275 flags, umask);
1276 break;
1277 default:
1278 ret = -EINVAL;
1279 }
1280
1281 path_put_and_out:
1282 path_put(&path);
1283 fput_and_out:
1284 fdput(f);
1285 return ret;
1286 }
1287
1288 #ifndef CONFIG_ARCH_SPLIT_ARG64
1289 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
1290 __u64, mask, int, dfd,
1291 const char __user *, pathname)
1292 {
1293 return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
1294 }
1295 #endif
1296
1297 #if defined(CONFIG_ARCH_SPLIT_ARG64) || defined(CONFIG_COMPAT)
1298 SYSCALL32_DEFINE6(fanotify_mark,
1299 int, fanotify_fd, unsigned int, flags,
1300 SC_ARG64(mask), int, dfd,
1301 const char __user *, pathname)
1302 {
1303 return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask),
1304 dfd, pathname);
1305 }
1306 #endif
1307
1308 /*
1309 * fanotify_user_setup - Our initialization function. Note that we cannot return
1310 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
1311 * must result in panic().
1312 */
1313 static int __init fanotify_user_setup(void)
1314 {
1315 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10);
1316 BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
1317
1318 fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
1319 SLAB_PANIC|SLAB_ACCOUNT);
1320 fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
1321 SLAB_PANIC);
1322 fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
1323 SLAB_PANIC);
1324 if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
1325 fanotify_perm_event_cachep =
1326 KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
1327 }
1328
1329 return 0;
1330 }
1331 device_initcall(fanotify_user_setup);
Linux with added FPC-III support