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Linux/fs/notify/fanotify/fanotify_user.c

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  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 
 20 #include <asm/ioctls.h>
 21 
 22 #include "../../mount.h"
 23 #include "../fdinfo.h"
 24 #include "fanotify.h"
 25 
 26 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
 27 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
 28 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
 29 
 30 /*
 31  * All flags that may be specified in parameter event_f_flags of fanotify_init.
 32  *
 33  * Internal and external open flags are stored together in field f_flags of
 34  * struct file. Only external open flags shall be allowed in event_f_flags.
 35  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
 36  * excluded.
 37  */
 38 #define FANOTIFY_INIT_ALL_EVENT_F_BITS                          ( \
 39                 O_ACCMODE       | O_APPEND      | O_NONBLOCK    | \
 40                 __O_SYNC        | O_DSYNC       | O_CLOEXEC     | \
 41                 O_LARGEFILE     | O_NOATIME     )
 42 
 43 extern const struct fsnotify_ops fanotify_fsnotify_ops;
 44 
 45 struct kmem_cache *fanotify_mark_cache __read_mostly;
 46 struct kmem_cache *fanotify_event_cachep __read_mostly;
 47 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
 48 
 49 /*
 50  * Get an fsnotify notification event if one exists and is small
 51  * enough to fit in "count". Return an error pointer if the count
 52  * is not large enough.
 53  *
 54  * Called with the group->notification_lock held.
 55  */
 56 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
 57                                             size_t count)
 58 {
 59         assert_spin_locked(&group->notification_lock);
 60 
 61         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
 62 
 63         if (fsnotify_notify_queue_is_empty(group))
 64                 return NULL;
 65 
 66         if (FAN_EVENT_METADATA_LEN > count)
 67                 return ERR_PTR(-EINVAL);
 68 
 69         /* held the notification_lock the whole time, so this is the
 70          * same event we peeked above */
 71         return fsnotify_remove_first_event(group);
 72 }
 73 
 74 static int create_fd(struct fsnotify_group *group,
 75                      struct fanotify_event_info *event,
 76                      struct file **file)
 77 {
 78         int client_fd;
 79         struct file *new_file;
 80 
 81         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 82 
 83         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
 84         if (client_fd < 0)
 85                 return client_fd;
 86 
 87         /*
 88          * we need a new file handle for the userspace program so it can read even if it was
 89          * originally opened O_WRONLY.
 90          */
 91         /* it's possible this event was an overflow event.  in that case dentry and mnt
 92          * are NULL;  That's fine, just don't call dentry open */
 93         if (event->path.dentry && event->path.mnt)
 94                 new_file = dentry_open(&event->path,
 95                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
 96                                        current_cred());
 97         else
 98                 new_file = ERR_PTR(-EOVERFLOW);
 99         if (IS_ERR(new_file)) {
100                 /*
101                  * we still send an event even if we can't open the file.  this
102                  * can happen when say tasks are gone and we try to open their
103                  * /proc files or we try to open a WRONLY file like in sysfs
104                  * we just send the errno to userspace since there isn't much
105                  * else we can do.
106                  */
107                 put_unused_fd(client_fd);
108                 client_fd = PTR_ERR(new_file);
109         } else {
110                 *file = new_file;
111         }
112 
113         return client_fd;
114 }
115 
116 static int fill_event_metadata(struct fsnotify_group *group,
117                                struct fanotify_event_metadata *metadata,
118                                struct fsnotify_event *fsn_event,
119                                struct file **file)
120 {
121         int ret = 0;
122         struct fanotify_event_info *event;
123 
124         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
125                  group, metadata, fsn_event);
126 
127         *file = NULL;
128         event = container_of(fsn_event, struct fanotify_event_info, fse);
129         metadata->event_len = FAN_EVENT_METADATA_LEN;
130         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
131         metadata->vers = FANOTIFY_METADATA_VERSION;
132         metadata->reserved = 0;
133         metadata->mask = fsn_event->mask & FAN_ALL_OUTGOING_EVENTS;
134         metadata->pid = pid_vnr(event->tgid);
135         if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
136                 metadata->fd = FAN_NOFD;
137         else {
138                 metadata->fd = create_fd(group, event, file);
139                 if (metadata->fd < 0)
140                         ret = metadata->fd;
141         }
142 
143         return ret;
144 }
145 
146 static struct fanotify_perm_event_info *dequeue_event(
147                                 struct fsnotify_group *group, int fd)
148 {
149         struct fanotify_perm_event_info *event, *return_e = NULL;
150 
151         spin_lock(&group->notification_lock);
152         list_for_each_entry(event, &group->fanotify_data.access_list,
153                             fae.fse.list) {
154                 if (event->fd != fd)
155                         continue;
156 
157                 list_del_init(&event->fae.fse.list);
158                 return_e = event;
159                 break;
160         }
161         spin_unlock(&group->notification_lock);
162 
163         pr_debug("%s: found return_re=%p\n", __func__, return_e);
164 
165         return return_e;
166 }
167 
168 static int process_access_response(struct fsnotify_group *group,
169                                    struct fanotify_response *response_struct)
170 {
171         struct fanotify_perm_event_info *event;
172         int fd = response_struct->fd;
173         int response = response_struct->response;
174 
175         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
176                  fd, response);
177         /*
178          * make sure the response is valid, if invalid we do nothing and either
179          * userspace can send a valid response or we will clean it up after the
180          * timeout
181          */
182         switch (response & ~FAN_AUDIT) {
183         case FAN_ALLOW:
184         case FAN_DENY:
185                 break;
186         default:
187                 return -EINVAL;
188         }
189 
190         if (fd < 0)
191                 return -EINVAL;
192 
193         if ((response & FAN_AUDIT) && !group->fanotify_data.audit)
194                 return -EINVAL;
195 
196         event = dequeue_event(group, fd);
197         if (!event)
198                 return -ENOENT;
199 
200         event->response = response;
201         wake_up(&group->fanotify_data.access_waitq);
202 
203         return 0;
204 }
205 
206 static ssize_t copy_event_to_user(struct fsnotify_group *group,
207                                   struct fsnotify_event *event,
208                                   char __user *buf)
209 {
210         struct fanotify_event_metadata fanotify_event_metadata;
211         struct file *f;
212         int fd, ret;
213 
214         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
215 
216         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
217         if (ret < 0)
218                 return ret;
219 
220         fd = fanotify_event_metadata.fd;
221         ret = -EFAULT;
222         if (copy_to_user(buf, &fanotify_event_metadata,
223                          fanotify_event_metadata.event_len))
224                 goto out_close_fd;
225 
226         if (fanotify_is_perm_event(event->mask))
227                 FANOTIFY_PE(event)->fd = fd;
228 
229         if (fd != FAN_NOFD)
230                 fd_install(fd, f);
231         return fanotify_event_metadata.event_len;
232 
233 out_close_fd:
234         if (fd != FAN_NOFD) {
235                 put_unused_fd(fd);
236                 fput(f);
237         }
238         return ret;
239 }
240 
241 /* intofiy userspace file descriptor functions */
242 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
243 {
244         struct fsnotify_group *group = file->private_data;
245         __poll_t ret = 0;
246 
247         poll_wait(file, &group->notification_waitq, wait);
248         spin_lock(&group->notification_lock);
249         if (!fsnotify_notify_queue_is_empty(group))
250                 ret = EPOLLIN | EPOLLRDNORM;
251         spin_unlock(&group->notification_lock);
252 
253         return ret;
254 }
255 
256 static ssize_t fanotify_read(struct file *file, char __user *buf,
257                              size_t count, loff_t *pos)
258 {
259         struct fsnotify_group *group;
260         struct fsnotify_event *kevent;
261         char __user *start;
262         int ret;
263         DEFINE_WAIT_FUNC(wait, woken_wake_function);
264 
265         start = buf;
266         group = file->private_data;
267 
268         pr_debug("%s: group=%p\n", __func__, group);
269 
270         add_wait_queue(&group->notification_waitq, &wait);
271         while (1) {
272                 spin_lock(&group->notification_lock);
273                 kevent = get_one_event(group, count);
274                 spin_unlock(&group->notification_lock);
275 
276                 if (IS_ERR(kevent)) {
277                         ret = PTR_ERR(kevent);
278                         break;
279                 }
280 
281                 if (!kevent) {
282                         ret = -EAGAIN;
283                         if (file->f_flags & O_NONBLOCK)
284                                 break;
285 
286                         ret = -ERESTARTSYS;
287                         if (signal_pending(current))
288                                 break;
289 
290                         if (start != buf)
291                                 break;
292 
293                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
294                         continue;
295                 }
296 
297                 ret = copy_event_to_user(group, kevent, buf);
298                 if (unlikely(ret == -EOPENSTALE)) {
299                         /*
300                          * We cannot report events with stale fd so drop it.
301                          * Setting ret to 0 will continue the event loop and
302                          * do the right thing if there are no more events to
303                          * read (i.e. return bytes read, -EAGAIN or wait).
304                          */
305                         ret = 0;
306                 }
307 
308                 /*
309                  * Permission events get queued to wait for response.  Other
310                  * events can be destroyed now.
311                  */
312                 if (!fanotify_is_perm_event(kevent->mask)) {
313                         fsnotify_destroy_event(group, kevent);
314                 } else {
315                         if (ret <= 0) {
316                                 FANOTIFY_PE(kevent)->response = FAN_DENY;
317                                 wake_up(&group->fanotify_data.access_waitq);
318                         } else {
319                                 spin_lock(&group->notification_lock);
320                                 list_add_tail(&kevent->list,
321                                         &group->fanotify_data.access_list);
322                                 spin_unlock(&group->notification_lock);
323                         }
324                 }
325                 if (ret < 0)
326                         break;
327                 buf += ret;
328                 count -= ret;
329         }
330         remove_wait_queue(&group->notification_waitq, &wait);
331 
332         if (start != buf && ret != -EFAULT)
333                 ret = buf - start;
334         return ret;
335 }
336 
337 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
338 {
339         struct fanotify_response response = { .fd = -1, .response = -1 };
340         struct fsnotify_group *group;
341         int ret;
342 
343         if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
344                 return -EINVAL;
345 
346         group = file->private_data;
347 
348         if (count > sizeof(response))
349                 count = sizeof(response);
350 
351         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
352 
353         if (copy_from_user(&response, buf, count))
354                 return -EFAULT;
355 
356         ret = process_access_response(group, &response);
357         if (ret < 0)
358                 count = ret;
359 
360         return count;
361 }
362 
363 static int fanotify_release(struct inode *ignored, struct file *file)
364 {
365         struct fsnotify_group *group = file->private_data;
366         struct fanotify_perm_event_info *event, *next;
367         struct fsnotify_event *fsn_event;
368 
369         /*
370          * Stop new events from arriving in the notification queue. since
371          * userspace cannot use fanotify fd anymore, no event can enter or
372          * leave access_list by now either.
373          */
374         fsnotify_group_stop_queueing(group);
375 
376         /*
377          * Process all permission events on access_list and notification queue
378          * and simulate reply from userspace.
379          */
380         spin_lock(&group->notification_lock);
381         list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
382                                  fae.fse.list) {
383                 pr_debug("%s: found group=%p event=%p\n", __func__, group,
384                          event);
385 
386                 list_del_init(&event->fae.fse.list);
387                 event->response = FAN_ALLOW;
388         }
389 
390         /*
391          * Destroy all non-permission events. For permission events just
392          * dequeue them and set the response. They will be freed once the
393          * response is consumed and fanotify_get_response() returns.
394          */
395         while (!fsnotify_notify_queue_is_empty(group)) {
396                 fsn_event = fsnotify_remove_first_event(group);
397                 if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
398                         spin_unlock(&group->notification_lock);
399                         fsnotify_destroy_event(group, fsn_event);
400                         spin_lock(&group->notification_lock);
401                 } else {
402                         FANOTIFY_PE(fsn_event)->response = FAN_ALLOW;
403                 }
404         }
405         spin_unlock(&group->notification_lock);
406 
407         /* Response for all permission events it set, wakeup waiters */
408         wake_up(&group->fanotify_data.access_waitq);
409 
410         /* matches the fanotify_init->fsnotify_alloc_group */
411         fsnotify_destroy_group(group);
412 
413         return 0;
414 }
415 
416 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
417 {
418         struct fsnotify_group *group;
419         struct fsnotify_event *fsn_event;
420         void __user *p;
421         int ret = -ENOTTY;
422         size_t send_len = 0;
423 
424         group = file->private_data;
425 
426         p = (void __user *) arg;
427 
428         switch (cmd) {
429         case FIONREAD:
430                 spin_lock(&group->notification_lock);
431                 list_for_each_entry(fsn_event, &group->notification_list, list)
432                         send_len += FAN_EVENT_METADATA_LEN;
433                 spin_unlock(&group->notification_lock);
434                 ret = put_user(send_len, (int __user *) p);
435                 break;
436         }
437 
438         return ret;
439 }
440 
441 static const struct file_operations fanotify_fops = {
442         .show_fdinfo    = fanotify_show_fdinfo,
443         .poll           = fanotify_poll,
444         .read           = fanotify_read,
445         .write          = fanotify_write,
446         .fasync         = NULL,
447         .release        = fanotify_release,
448         .unlocked_ioctl = fanotify_ioctl,
449         .compat_ioctl   = fanotify_ioctl,
450         .llseek         = noop_llseek,
451 };
452 
453 static int fanotify_find_path(int dfd, const char __user *filename,
454                               struct path *path, unsigned int flags)
455 {
456         int ret;
457 
458         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
459                  dfd, filename, flags);
460 
461         if (filename == NULL) {
462                 struct fd f = fdget(dfd);
463 
464                 ret = -EBADF;
465                 if (!f.file)
466                         goto out;
467 
468                 ret = -ENOTDIR;
469                 if ((flags & FAN_MARK_ONLYDIR) &&
470                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
471                         fdput(f);
472                         goto out;
473                 }
474 
475                 *path = f.file->f_path;
476                 path_get(path);
477                 fdput(f);
478         } else {
479                 unsigned int lookup_flags = 0;
480 
481                 if (!(flags & FAN_MARK_DONT_FOLLOW))
482                         lookup_flags |= LOOKUP_FOLLOW;
483                 if (flags & FAN_MARK_ONLYDIR)
484                         lookup_flags |= LOOKUP_DIRECTORY;
485 
486                 ret = user_path_at(dfd, filename, lookup_flags, path);
487                 if (ret)
488                         goto out;
489         }
490 
491         /* you can only watch an inode if you have read permissions on it */
492         ret = inode_permission(path->dentry->d_inode, MAY_READ);
493         if (ret)
494                 path_put(path);
495 out:
496         return ret;
497 }
498 
499 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
500                                             __u32 mask,
501                                             unsigned int flags,
502                                             int *destroy)
503 {
504         __u32 oldmask = 0;
505 
506         spin_lock(&fsn_mark->lock);
507         if (!(flags & FAN_MARK_IGNORED_MASK)) {
508                 __u32 tmask = fsn_mark->mask & ~mask;
509 
510                 if (flags & FAN_MARK_ONDIR)
511                         tmask &= ~FAN_ONDIR;
512 
513                 oldmask = fsn_mark->mask;
514                 fsn_mark->mask = tmask;
515         } else {
516                 __u32 tmask = fsn_mark->ignored_mask & ~mask;
517                 if (flags & FAN_MARK_ONDIR)
518                         tmask &= ~FAN_ONDIR;
519                 fsn_mark->ignored_mask = tmask;
520         }
521         *destroy = !(fsn_mark->mask | fsn_mark->ignored_mask);
522         spin_unlock(&fsn_mark->lock);
523 
524         return mask & oldmask;
525 }
526 
527 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
528                                          struct vfsmount *mnt, __u32 mask,
529                                          unsigned int flags)
530 {
531         struct fsnotify_mark *fsn_mark = NULL;
532         __u32 removed;
533         int destroy_mark;
534 
535         mutex_lock(&group->mark_mutex);
536         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
537                                       group);
538         if (!fsn_mark) {
539                 mutex_unlock(&group->mark_mutex);
540                 return -ENOENT;
541         }
542 
543         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
544                                                  &destroy_mark);
545         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
546                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
547         if (destroy_mark)
548                 fsnotify_detach_mark(fsn_mark);
549         mutex_unlock(&group->mark_mutex);
550         if (destroy_mark)
551                 fsnotify_free_mark(fsn_mark);
552 
553         fsnotify_put_mark(fsn_mark);
554         return 0;
555 }
556 
557 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
558                                       struct inode *inode, __u32 mask,
559                                       unsigned int flags)
560 {
561         struct fsnotify_mark *fsn_mark = NULL;
562         __u32 removed;
563         int destroy_mark;
564 
565         mutex_lock(&group->mark_mutex);
566         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
567         if (!fsn_mark) {
568                 mutex_unlock(&group->mark_mutex);
569                 return -ENOENT;
570         }
571 
572         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
573                                                  &destroy_mark);
574         if (removed & inode->i_fsnotify_mask)
575                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
576         if (destroy_mark)
577                 fsnotify_detach_mark(fsn_mark);
578         mutex_unlock(&group->mark_mutex);
579         if (destroy_mark)
580                 fsnotify_free_mark(fsn_mark);
581 
582         /* matches the fsnotify_find_mark() */
583         fsnotify_put_mark(fsn_mark);
584 
585         return 0;
586 }
587 
588 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
589                                        __u32 mask,
590                                        unsigned int flags)
591 {
592         __u32 oldmask = -1;
593 
594         spin_lock(&fsn_mark->lock);
595         if (!(flags & FAN_MARK_IGNORED_MASK)) {
596                 __u32 tmask = fsn_mark->mask | mask;
597 
598                 if (flags & FAN_MARK_ONDIR)
599                         tmask |= FAN_ONDIR;
600 
601                 oldmask = fsn_mark->mask;
602                 fsn_mark->mask = tmask;
603         } else {
604                 __u32 tmask = fsn_mark->ignored_mask | mask;
605                 if (flags & FAN_MARK_ONDIR)
606                         tmask |= FAN_ONDIR;
607 
608                 fsn_mark->ignored_mask = tmask;
609                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
610                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
611         }
612         spin_unlock(&fsn_mark->lock);
613 
614         return mask & ~oldmask;
615 }
616 
617 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
618                                                    struct inode *inode,
619                                                    struct vfsmount *mnt)
620 {
621         struct fsnotify_mark *mark;
622         int ret;
623 
624         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
625                 return ERR_PTR(-ENOSPC);
626 
627         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
628         if (!mark)
629                 return ERR_PTR(-ENOMEM);
630 
631         fsnotify_init_mark(mark, group);
632         ret = fsnotify_add_mark_locked(mark, inode, mnt, 0);
633         if (ret) {
634                 fsnotify_put_mark(mark);
635                 return ERR_PTR(ret);
636         }
637 
638         return mark;
639 }
640 
641 
642 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
643                                       struct vfsmount *mnt, __u32 mask,
644                                       unsigned int flags)
645 {
646         struct fsnotify_mark *fsn_mark;
647         __u32 added;
648 
649         mutex_lock(&group->mark_mutex);
650         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
651                                       group);
652         if (!fsn_mark) {
653                 fsn_mark = fanotify_add_new_mark(group, NULL, mnt);
654                 if (IS_ERR(fsn_mark)) {
655                         mutex_unlock(&group->mark_mutex);
656                         return PTR_ERR(fsn_mark);
657                 }
658         }
659         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
660         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
661                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
662         mutex_unlock(&group->mark_mutex);
663 
664         fsnotify_put_mark(fsn_mark);
665         return 0;
666 }
667 
668 static int fanotify_add_inode_mark(struct fsnotify_group *group,
669                                    struct inode *inode, __u32 mask,
670                                    unsigned int flags)
671 {
672         struct fsnotify_mark *fsn_mark;
673         __u32 added;
674 
675         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
676 
677         /*
678          * If some other task has this inode open for write we should not add
679          * an ignored mark, unless that ignored mark is supposed to survive
680          * modification changes anyway.
681          */
682         if ((flags & FAN_MARK_IGNORED_MASK) &&
683             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
684             (atomic_read(&inode->i_writecount) > 0))
685                 return 0;
686 
687         mutex_lock(&group->mark_mutex);
688         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
689         if (!fsn_mark) {
690                 fsn_mark = fanotify_add_new_mark(group, inode, NULL);
691                 if (IS_ERR(fsn_mark)) {
692                         mutex_unlock(&group->mark_mutex);
693                         return PTR_ERR(fsn_mark);
694                 }
695         }
696         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
697         if (added & ~inode->i_fsnotify_mask)
698                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
699         mutex_unlock(&group->mark_mutex);
700 
701         fsnotify_put_mark(fsn_mark);
702         return 0;
703 }
704 
705 /* fanotify syscalls */
706 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
707 {
708         struct fsnotify_group *group;
709         int f_flags, fd;
710         struct user_struct *user;
711         struct fanotify_event_info *oevent;
712 
713         pr_debug("%s: flags=%d event_f_flags=%d\n",
714                 __func__, flags, event_f_flags);
715 
716         if (!capable(CAP_SYS_ADMIN))
717                 return -EPERM;
718 
719 #ifdef CONFIG_AUDITSYSCALL
720         if (flags & ~(FAN_ALL_INIT_FLAGS | FAN_ENABLE_AUDIT))
721 #else
722         if (flags & ~FAN_ALL_INIT_FLAGS)
723 #endif
724                 return -EINVAL;
725 
726         if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
727                 return -EINVAL;
728 
729         switch (event_f_flags & O_ACCMODE) {
730         case O_RDONLY:
731         case O_RDWR:
732         case O_WRONLY:
733                 break;
734         default:
735                 return -EINVAL;
736         }
737 
738         user = get_current_user();
739         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
740                 free_uid(user);
741                 return -EMFILE;
742         }
743 
744         f_flags = O_RDWR | FMODE_NONOTIFY;
745         if (flags & FAN_CLOEXEC)
746                 f_flags |= O_CLOEXEC;
747         if (flags & FAN_NONBLOCK)
748                 f_flags |= O_NONBLOCK;
749 
750         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
751         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
752         if (IS_ERR(group)) {
753                 free_uid(user);
754                 return PTR_ERR(group);
755         }
756 
757         group->fanotify_data.user = user;
758         atomic_inc(&user->fanotify_listeners);
759 
760         oevent = fanotify_alloc_event(group, NULL, FS_Q_OVERFLOW, NULL);
761         if (unlikely(!oevent)) {
762                 fd = -ENOMEM;
763                 goto out_destroy_group;
764         }
765         group->overflow_event = &oevent->fse;
766 
767         if (force_o_largefile())
768                 event_f_flags |= O_LARGEFILE;
769         group->fanotify_data.f_flags = event_f_flags;
770         init_waitqueue_head(&group->fanotify_data.access_waitq);
771         INIT_LIST_HEAD(&group->fanotify_data.access_list);
772         switch (flags & FAN_ALL_CLASS_BITS) {
773         case FAN_CLASS_NOTIF:
774                 group->priority = FS_PRIO_0;
775                 break;
776         case FAN_CLASS_CONTENT:
777                 group->priority = FS_PRIO_1;
778                 break;
779         case FAN_CLASS_PRE_CONTENT:
780                 group->priority = FS_PRIO_2;
781                 break;
782         default:
783                 fd = -EINVAL;
784                 goto out_destroy_group;
785         }
786 
787         if (flags & FAN_UNLIMITED_QUEUE) {
788                 fd = -EPERM;
789                 if (!capable(CAP_SYS_ADMIN))
790                         goto out_destroy_group;
791                 group->max_events = UINT_MAX;
792         } else {
793                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
794         }
795 
796         if (flags & FAN_UNLIMITED_MARKS) {
797                 fd = -EPERM;
798                 if (!capable(CAP_SYS_ADMIN))
799                         goto out_destroy_group;
800                 group->fanotify_data.max_marks = UINT_MAX;
801         } else {
802                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
803         }
804 
805         if (flags & FAN_ENABLE_AUDIT) {
806                 fd = -EPERM;
807                 if (!capable(CAP_AUDIT_WRITE))
808                         goto out_destroy_group;
809                 group->fanotify_data.audit = true;
810         }
811 
812         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
813         if (fd < 0)
814                 goto out_destroy_group;
815 
816         return fd;
817 
818 out_destroy_group:
819         fsnotify_destroy_group(group);
820         return fd;
821 }
822 
823 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
824                             int dfd, const char  __user *pathname)
825 {
826         struct inode *inode = NULL;
827         struct vfsmount *mnt = NULL;
828         struct fsnotify_group *group;
829         struct fd f;
830         struct path path;
831         u32 valid_mask = FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD;
832         int ret;
833 
834         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
835                  __func__, fanotify_fd, flags, dfd, pathname, mask);
836 
837         /* we only use the lower 32 bits as of right now. */
838         if (mask & ((__u64)0xffffffff << 32))
839                 return -EINVAL;
840 
841         if (flags & ~FAN_ALL_MARK_FLAGS)
842                 return -EINVAL;
843         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
844         case FAN_MARK_ADD:              /* fallthrough */
845         case FAN_MARK_REMOVE:
846                 if (!mask)
847                         return -EINVAL;
848                 break;
849         case FAN_MARK_FLUSH:
850                 if (flags & ~(FAN_MARK_MOUNT | FAN_MARK_FLUSH))
851                         return -EINVAL;
852                 break;
853         default:
854                 return -EINVAL;
855         }
856 
857         if (mask & FAN_ONDIR) {
858                 flags |= FAN_MARK_ONDIR;
859                 mask &= ~FAN_ONDIR;
860         }
861 
862         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
863                 valid_mask |= FAN_ALL_PERM_EVENTS;
864 
865         if (mask & ~valid_mask)
866                 return -EINVAL;
867 
868         f = fdget(fanotify_fd);
869         if (unlikely(!f.file))
870                 return -EBADF;
871 
872         /* verify that this is indeed an fanotify instance */
873         ret = -EINVAL;
874         if (unlikely(f.file->f_op != &fanotify_fops))
875                 goto fput_and_out;
876         group = f.file->private_data;
877 
878         /*
879          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
880          * allowed to set permissions events.
881          */
882         ret = -EINVAL;
883         if (mask & FAN_ALL_PERM_EVENTS &&
884             group->priority == FS_PRIO_0)
885                 goto fput_and_out;
886 
887         if (flags & FAN_MARK_FLUSH) {
888                 ret = 0;
889                 if (flags & FAN_MARK_MOUNT)
890                         fsnotify_clear_vfsmount_marks_by_group(group);
891                 else
892                         fsnotify_clear_inode_marks_by_group(group);
893                 goto fput_and_out;
894         }
895 
896         ret = fanotify_find_path(dfd, pathname, &path, flags);
897         if (ret)
898                 goto fput_and_out;
899 
900         /* inode held in place by reference to path; group by fget on fd */
901         if (!(flags & FAN_MARK_MOUNT))
902                 inode = path.dentry->d_inode;
903         else
904                 mnt = path.mnt;
905 
906         /* create/update an inode mark */
907         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
908         case FAN_MARK_ADD:
909                 if (flags & FAN_MARK_MOUNT)
910                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
911                 else
912                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
913                 break;
914         case FAN_MARK_REMOVE:
915                 if (flags & FAN_MARK_MOUNT)
916                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
917                 else
918                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
919                 break;
920         default:
921                 ret = -EINVAL;
922         }
923 
924         path_put(&path);
925 fput_and_out:
926         fdput(f);
927         return ret;
928 }
929 
930 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
931                               __u64, mask, int, dfd,
932                               const char  __user *, pathname)
933 {
934         return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
935 }
936 
937 #ifdef CONFIG_COMPAT
938 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
939                                 int, fanotify_fd, unsigned int, flags,
940                                 __u32, mask0, __u32, mask1, int, dfd,
941                                 const char  __user *, pathname)
942 {
943         return do_fanotify_mark(fanotify_fd, flags,
944 #ifdef __BIG_ENDIAN
945                                 ((__u64)mask0 << 32) | mask1,
946 #else
947                                 ((__u64)mask1 << 32) | mask0,
948 #endif
949                                  dfd, pathname);
950 }
951 #endif
952 
953 /*
954  * fanotify_user_setup - Our initialization function.  Note that we cannot return
955  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
956  * must result in panic().
957  */
958 static int __init fanotify_user_setup(void)
959 {
960         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
961         fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
962         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
963                 fanotify_perm_event_cachep =
964                         KMEM_CACHE(fanotify_perm_event_info, SLAB_PANIC);
965         }
966 
967         return 0;
968 }
969 device_initcall(fanotify_user_setup);
970 

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