1 #include <linux/fanotify.h>
2 #include <linux/fcntl.h>
3 #include <linux/file.h>
5 #include <linux/anon_inodes.h>
6 #include <linux/fsnotify_backend.h>
7 #include <linux/init.h>
8 #include <linux/mount.h>
9 #include <linux/namei.h>
10 #include <linux/poll.h>
11 #include <linux/security.h>
12 #include <linux/syscalls.h>
13 #include <linux/slab.h>
14 #include <linux/types.h>
15 #include <linux/uaccess.h>
17 #include <asm/ioctls.h>
19 #include "../../mount.h"
21 #define FANOTIFY_DEFAULT_MAX_EVENTS 16384
22 #define FANOTIFY_DEFAULT_MAX_MARKS 8192
23 #define FANOTIFY_DEFAULT_MAX_LISTENERS 128
25 extern const struct fsnotify_ops fanotify_fsnotify_ops;
27 static struct kmem_cache *fanotify_mark_cache __read_mostly;
28 static struct kmem_cache *fanotify_response_event_cache __read_mostly;
30 struct fanotify_response_event {
31 struct list_head list;
33 struct fsnotify_event *event;
37 * Get an fsnotify notification event if one exists and is small
38 * enough to fit in "count". Return an error pointer if the count
39 * is not large enough.
41 * Called with the group->notification_mutex held.
43 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
46 BUG_ON(!mutex_is_locked(&group->notification_mutex));
48 pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
50 if (fsnotify_notify_queue_is_empty(group))
53 if (FAN_EVENT_METADATA_LEN > count)
54 return ERR_PTR(-EINVAL);
56 /* held the notification_mutex the whole time, so this is the
57 * same event we peeked above */
58 return fsnotify_remove_notify_event(group);
61 static int create_fd(struct fsnotify_group *group,
62 struct fsnotify_event *event,
66 struct file *new_file;
68 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
70 client_fd = get_unused_fd();
74 if (event->data_type != FSNOTIFY_EVENT_PATH) {
76 put_unused_fd(client_fd);
81 * we need a new file handle for the userspace program so it can read even if it was
82 * originally opened O_WRONLY.
84 /* it's possible this event was an overflow event. in that case dentry and mnt
85 * are NULL; That's fine, just don't call dentry open */
86 if (event->path.dentry && event->path.mnt)
87 new_file = dentry_open(&event->path,
88 group->fanotify_data.f_flags | FMODE_NONOTIFY,
91 new_file = ERR_PTR(-EOVERFLOW);
92 if (IS_ERR(new_file)) {
94 * we still send an event even if we can't open the file. this
95 * can happen when say tasks are gone and we try to open their
96 * /proc files or we try to open a WRONLY file like in sysfs
97 * we just send the errno to userspace since there isn't much
100 put_unused_fd(client_fd);
101 client_fd = PTR_ERR(new_file);
109 static int fill_event_metadata(struct fsnotify_group *group,
110 struct fanotify_event_metadata *metadata,
111 struct fsnotify_event *event,
116 pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
117 group, metadata, event);
120 metadata->event_len = FAN_EVENT_METADATA_LEN;
121 metadata->metadata_len = FAN_EVENT_METADATA_LEN;
122 metadata->vers = FANOTIFY_METADATA_VERSION;
123 metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
124 metadata->pid = pid_vnr(event->tgid);
125 if (unlikely(event->mask & FAN_Q_OVERFLOW))
126 metadata->fd = FAN_NOFD;
128 metadata->fd = create_fd(group, event, file);
129 if (metadata->fd < 0)
136 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
137 static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
140 struct fanotify_response_event *re, *return_re = NULL;
142 mutex_lock(&group->fanotify_data.access_mutex);
143 list_for_each_entry(re, &group->fanotify_data.access_list, list) {
147 list_del_init(&re->list);
151 mutex_unlock(&group->fanotify_data.access_mutex);
153 pr_debug("%s: found return_re=%p\n", __func__, return_re);
158 static int process_access_response(struct fsnotify_group *group,
159 struct fanotify_response *response_struct)
161 struct fanotify_response_event *re;
162 __s32 fd = response_struct->fd;
163 __u32 response = response_struct->response;
165 pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
168 * make sure the response is valid, if invalid we do nothing and either
169 * userspace can send a valid response or we will clean it up after the
183 re = dequeue_re(group, fd);
187 re->event->response = response;
189 wake_up(&group->fanotify_data.access_waitq);
191 kmem_cache_free(fanotify_response_event_cache, re);
196 static int prepare_for_access_response(struct fsnotify_group *group,
197 struct fsnotify_event *event,
200 struct fanotify_response_event *re;
202 if (!(event->mask & FAN_ALL_PERM_EVENTS))
205 re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
212 mutex_lock(&group->fanotify_data.access_mutex);
214 if (atomic_read(&group->fanotify_data.bypass_perm)) {
215 mutex_unlock(&group->fanotify_data.access_mutex);
216 kmem_cache_free(fanotify_response_event_cache, re);
217 event->response = FAN_ALLOW;
221 list_add_tail(&re->list, &group->fanotify_data.access_list);
222 mutex_unlock(&group->fanotify_data.access_mutex);
228 static int prepare_for_access_response(struct fsnotify_group *group,
229 struct fsnotify_event *event,
237 static ssize_t copy_event_to_user(struct fsnotify_group *group,
238 struct fsnotify_event *event,
241 struct fanotify_event_metadata fanotify_event_metadata;
245 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
247 ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
251 fd = fanotify_event_metadata.fd;
253 if (copy_to_user(buf, &fanotify_event_metadata,
254 fanotify_event_metadata.event_len))
257 ret = prepare_for_access_response(group, event, fd);
262 return fanotify_event_metadata.event_len;
265 if (fd != FAN_NOFD) {
270 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
271 if (event->mask & FAN_ALL_PERM_EVENTS) {
272 event->response = FAN_DENY;
273 wake_up(&group->fanotify_data.access_waitq);
279 /* intofiy userspace file descriptor functions */
280 static unsigned int fanotify_poll(struct file *file, poll_table *wait)
282 struct fsnotify_group *group = file->private_data;
285 poll_wait(file, &group->notification_waitq, wait);
286 mutex_lock(&group->notification_mutex);
287 if (!fsnotify_notify_queue_is_empty(group))
288 ret = POLLIN | POLLRDNORM;
289 mutex_unlock(&group->notification_mutex);
294 static ssize_t fanotify_read(struct file *file, char __user *buf,
295 size_t count, loff_t *pos)
297 struct fsnotify_group *group;
298 struct fsnotify_event *kevent;
304 group = file->private_data;
306 pr_debug("%s: group=%p\n", __func__, group);
309 prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
311 mutex_lock(&group->notification_mutex);
312 kevent = get_one_event(group, count);
313 mutex_unlock(&group->notification_mutex);
316 ret = PTR_ERR(kevent);
319 ret = copy_event_to_user(group, kevent, buf);
320 fsnotify_put_event(kevent);
329 if (file->f_flags & O_NONBLOCK)
332 if (signal_pending(current))
341 finish_wait(&group->notification_waitq, &wait);
342 if (start != buf && ret != -EFAULT)
347 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
349 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
350 struct fanotify_response response = { .fd = -1, .response = -1 };
351 struct fsnotify_group *group;
354 group = file->private_data;
356 if (count > sizeof(response))
357 count = sizeof(response);
359 pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
361 if (copy_from_user(&response, buf, count))
364 ret = process_access_response(group, &response);
374 static int fanotify_release(struct inode *ignored, struct file *file)
376 struct fsnotify_group *group = file->private_data;
378 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
379 struct fanotify_response_event *re, *lre;
381 mutex_lock(&group->fanotify_data.access_mutex);
383 atomic_inc(&group->fanotify_data.bypass_perm);
385 list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
386 pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
389 list_del_init(&re->list);
390 re->event->response = FAN_ALLOW;
392 kmem_cache_free(fanotify_response_event_cache, re);
394 mutex_unlock(&group->fanotify_data.access_mutex);
396 wake_up(&group->fanotify_data.access_waitq);
398 /* matches the fanotify_init->fsnotify_alloc_group */
399 fsnotify_put_group(group);
404 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
406 struct fsnotify_group *group;
407 struct fsnotify_event_holder *holder;
412 group = file->private_data;
414 p = (void __user *) arg;
418 mutex_lock(&group->notification_mutex);
419 list_for_each_entry(holder, &group->notification_list, event_list)
420 send_len += FAN_EVENT_METADATA_LEN;
421 mutex_unlock(&group->notification_mutex);
422 ret = put_user(send_len, (int __user *) p);
429 static const struct file_operations fanotify_fops = {
430 .poll = fanotify_poll,
431 .read = fanotify_read,
432 .write = fanotify_write,
434 .release = fanotify_release,
435 .unlocked_ioctl = fanotify_ioctl,
436 .compat_ioctl = fanotify_ioctl,
437 .llseek = noop_llseek,
440 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
442 kmem_cache_free(fanotify_mark_cache, fsn_mark);
445 static int fanotify_find_path(int dfd, const char __user *filename,
446 struct path *path, unsigned int flags)
450 pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
451 dfd, filename, flags);
453 if (filename == NULL) {
454 struct fd f = fdget(dfd);
461 if ((flags & FAN_MARK_ONLYDIR) &&
462 !(S_ISDIR(f.file->f_path.dentry->d_inode->i_mode))) {
467 *path = f.file->f_path;
471 unsigned int lookup_flags = 0;
473 if (!(flags & FAN_MARK_DONT_FOLLOW))
474 lookup_flags |= LOOKUP_FOLLOW;
475 if (flags & FAN_MARK_ONLYDIR)
476 lookup_flags |= LOOKUP_DIRECTORY;
478 ret = user_path_at(dfd, filename, lookup_flags, path);
483 /* you can only watch an inode if you have read permissions on it */
484 ret = inode_permission(path->dentry->d_inode, MAY_READ);
491 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
497 spin_lock(&fsn_mark->lock);
498 if (!(flags & FAN_MARK_IGNORED_MASK)) {
499 oldmask = fsn_mark->mask;
500 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask & ~mask));
502 oldmask = fsn_mark->ignored_mask;
503 fsnotify_set_mark_ignored_mask_locked(fsn_mark, (oldmask & ~mask));
505 spin_unlock(&fsn_mark->lock);
507 if (!(oldmask & ~mask))
508 fsnotify_destroy_mark(fsn_mark);
510 return mask & oldmask;
513 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
514 struct vfsmount *mnt, __u32 mask,
517 struct fsnotify_mark *fsn_mark = NULL;
520 fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
524 removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags);
525 fsnotify_put_mark(fsn_mark);
526 if (removed & real_mount(mnt)->mnt_fsnotify_mask)
527 fsnotify_recalc_vfsmount_mask(mnt);
532 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
533 struct inode *inode, __u32 mask,
536 struct fsnotify_mark *fsn_mark = NULL;
539 fsn_mark = fsnotify_find_inode_mark(group, inode);
543 removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags);
544 /* matches the fsnotify_find_inode_mark() */
545 fsnotify_put_mark(fsn_mark);
546 if (removed & inode->i_fsnotify_mask)
547 fsnotify_recalc_inode_mask(inode);
552 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
558 spin_lock(&fsn_mark->lock);
559 if (!(flags & FAN_MARK_IGNORED_MASK)) {
560 oldmask = fsn_mark->mask;
561 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask | mask));
563 __u32 tmask = fsn_mark->ignored_mask | mask;
564 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
565 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
566 fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
569 if (!(flags & FAN_MARK_ONDIR)) {
570 __u32 tmask = fsn_mark->ignored_mask | FAN_ONDIR;
571 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
574 spin_unlock(&fsn_mark->lock);
576 return mask & ~oldmask;
579 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
580 struct vfsmount *mnt, __u32 mask,
583 struct fsnotify_mark *fsn_mark;
587 fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
589 if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
592 fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
596 fsnotify_init_mark(fsn_mark, fanotify_free_mark);
597 ret = fsnotify_add_mark(fsn_mark, group, NULL, mnt, 0);
601 added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
603 if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
604 fsnotify_recalc_vfsmount_mask(mnt);
606 fsnotify_put_mark(fsn_mark);
610 static int fanotify_add_inode_mark(struct fsnotify_group *group,
611 struct inode *inode, __u32 mask,
614 struct fsnotify_mark *fsn_mark;
618 pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
621 * If some other task has this inode open for write we should not add
622 * an ignored mark, unless that ignored mark is supposed to survive
623 * modification changes anyway.
625 if ((flags & FAN_MARK_IGNORED_MASK) &&
626 !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
627 (atomic_read(&inode->i_writecount) > 0))
630 fsn_mark = fsnotify_find_inode_mark(group, inode);
632 if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
635 fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
639 fsnotify_init_mark(fsn_mark, fanotify_free_mark);
640 ret = fsnotify_add_mark(fsn_mark, group, inode, NULL, 0);
644 added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
646 if (added & ~inode->i_fsnotify_mask)
647 fsnotify_recalc_inode_mask(inode);
649 fsnotify_put_mark(fsn_mark);
653 /* fanotify syscalls */
654 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
656 struct fsnotify_group *group;
658 struct user_struct *user;
660 pr_debug("%s: flags=%d event_f_flags=%d\n",
661 __func__, flags, event_f_flags);
663 if (!capable(CAP_SYS_ADMIN))
666 if (flags & ~FAN_ALL_INIT_FLAGS)
669 user = get_current_user();
670 if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
675 f_flags = O_RDWR | FMODE_NONOTIFY;
676 if (flags & FAN_CLOEXEC)
677 f_flags |= O_CLOEXEC;
678 if (flags & FAN_NONBLOCK)
679 f_flags |= O_NONBLOCK;
681 /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
682 group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
685 return PTR_ERR(group);
688 group->fanotify_data.user = user;
689 atomic_inc(&user->fanotify_listeners);
691 group->fanotify_data.f_flags = event_f_flags;
692 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
693 mutex_init(&group->fanotify_data.access_mutex);
694 init_waitqueue_head(&group->fanotify_data.access_waitq);
695 INIT_LIST_HEAD(&group->fanotify_data.access_list);
696 atomic_set(&group->fanotify_data.bypass_perm, 0);
698 switch (flags & FAN_ALL_CLASS_BITS) {
699 case FAN_CLASS_NOTIF:
700 group->priority = FS_PRIO_0;
702 case FAN_CLASS_CONTENT:
703 group->priority = FS_PRIO_1;
705 case FAN_CLASS_PRE_CONTENT:
706 group->priority = FS_PRIO_2;
713 if (flags & FAN_UNLIMITED_QUEUE) {
715 if (!capable(CAP_SYS_ADMIN))
717 group->max_events = UINT_MAX;
719 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
722 if (flags & FAN_UNLIMITED_MARKS) {
724 if (!capable(CAP_SYS_ADMIN))
726 group->fanotify_data.max_marks = UINT_MAX;
728 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
731 fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
738 fsnotify_put_group(group);
742 SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int flags,
744 const char __user * pathname)
746 struct inode *inode = NULL;
747 struct vfsmount *mnt = NULL;
748 struct fsnotify_group *group;
753 pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
754 __func__, fanotify_fd, flags, dfd, pathname, mask);
756 /* we only use the lower 32 bits as of right now. */
757 if (mask & ((__u64)0xffffffff << 32))
760 if (flags & ~FAN_ALL_MARK_FLAGS)
762 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
763 case FAN_MARK_ADD: /* fallthrough */
764 case FAN_MARK_REMOVE:
773 if (mask & FAN_ONDIR) {
774 flags |= FAN_MARK_ONDIR;
778 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
779 if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
781 if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
785 f = fdget(fanotify_fd);
786 if (unlikely(!f.file))
789 /* verify that this is indeed an fanotify instance */
791 if (unlikely(f.file->f_op != &fanotify_fops))
793 group = f.file->private_data;
796 * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF. These are not
797 * allowed to set permissions events.
800 if (mask & FAN_ALL_PERM_EVENTS &&
801 group->priority == FS_PRIO_0)
804 ret = fanotify_find_path(dfd, pathname, &path, flags);
808 /* inode held in place by reference to path; group by fget on fd */
809 if (!(flags & FAN_MARK_MOUNT))
810 inode = path.dentry->d_inode;
814 /* create/update an inode mark */
815 switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
817 if (flags & FAN_MARK_MOUNT)
818 ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
820 ret = fanotify_add_inode_mark(group, inode, mask, flags);
822 case FAN_MARK_REMOVE:
823 if (flags & FAN_MARK_MOUNT)
824 ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
826 ret = fanotify_remove_inode_mark(group, inode, mask, flags);
829 if (flags & FAN_MARK_MOUNT)
830 fsnotify_clear_vfsmount_marks_by_group(group);
832 fsnotify_clear_inode_marks_by_group(group);
844 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
845 asmlinkage long SyS_fanotify_mark(long fanotify_fd, long flags, __u64 mask,
846 long dfd, long pathname)
848 return SYSC_fanotify_mark((int) fanotify_fd, (unsigned int) flags,
850 (const char __user *) pathname);
852 SYSCALL_ALIAS(sys_fanotify_mark, SyS_fanotify_mark);
856 * fanotify_user_setup - Our initialization function. Note that we cannot return
857 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
858 * must result in panic().
860 static int __init fanotify_user_setup(void)
862 fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
863 fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
868 device_initcall(fanotify_user_setup);