2 * fs/inotify_user.c - inotify support for userspace
5 * John McCutchan <ttb@tentacle.dhs.org>
6 * Robert Love <rml@novell.com>
8 * Copyright (C) 2005 John McCutchan
9 * Copyright 2006 Hewlett-Packard Development Company, L.P.
11 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
12 * inotify was largely rewriten to make use of the fsnotify infrastructure
14 * This program is free software; you can redistribute it and/or modify it
15 * under the terms of the GNU General Public License as published by the
16 * Free Software Foundation; either version 2, or (at your option) any
19 * This program is distributed in the hope that it will be useful, but
20 * WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22 * General Public License for more details.
25 #include <linux/file.h>
26 #include <linux/fs.h> /* struct inode */
27 #include <linux/fsnotify_backend.h>
28 #include <linux/idr.h>
29 #include <linux/init.h> /* module_init */
30 #include <linux/inotify.h>
31 #include <linux/kernel.h> /* roundup() */
32 #include <linux/namei.h> /* LOOKUP_FOLLOW */
33 #include <linux/sched.h> /* struct user */
34 #include <linux/slab.h> /* struct kmem_cache */
35 #include <linux/syscalls.h>
36 #include <linux/types.h>
37 #include <linux/anon_inodes.h>
38 #include <linux/uaccess.h>
39 #include <linux/poll.h>
40 #include <linux/wait.h>
44 #include <asm/ioctls.h>
46 /* these are configurable via /proc/sys/fs/inotify/ */
47 static int inotify_max_user_instances __read_mostly
;
48 static int inotify_max_queued_events __read_mostly
;
49 int inotify_max_user_watches __read_mostly
;
51 static struct kmem_cache
*inotify_inode_mark_cachep __read_mostly
;
52 struct kmem_cache
*event_priv_cachep __read_mostly
;
55 * When inotify registers a new group it increments this and uses that
56 * value as an offset to set the fsnotify group "name" and priority.
58 static atomic_t inotify_grp_num
;
62 #include <linux/sysctl.h>
66 ctl_table inotify_table
[] = {
68 .procname
= "max_user_instances",
69 .data
= &inotify_max_user_instances
,
70 .maxlen
= sizeof(int),
72 .proc_handler
= proc_dointvec_minmax
,
76 .procname
= "max_user_watches",
77 .data
= &inotify_max_user_watches
,
78 .maxlen
= sizeof(int),
80 .proc_handler
= proc_dointvec_minmax
,
84 .procname
= "max_queued_events",
85 .data
= &inotify_max_queued_events
,
86 .maxlen
= sizeof(int),
88 .proc_handler
= proc_dointvec_minmax
,
93 #endif /* CONFIG_SYSCTL */
95 static inline __u32
inotify_arg_to_mask(u32 arg
)
99 /* everything should accept their own ignored and cares about children */
100 mask
= (FS_IN_IGNORED
| FS_EVENT_ON_CHILD
);
102 /* mask off the flags used to open the fd */
103 mask
|= (arg
& (IN_ALL_EVENTS
| IN_ONESHOT
));
108 static inline u32
inotify_mask_to_arg(__u32 mask
)
110 return mask
& (IN_ALL_EVENTS
| IN_ISDIR
| IN_UNMOUNT
| IN_IGNORED
|
114 /* intofiy userspace file descriptor functions */
115 static unsigned int inotify_poll(struct file
*file
, poll_table
*wait
)
117 struct fsnotify_group
*group
= file
->private_data
;
120 poll_wait(file
, &group
->notification_waitq
, wait
);
121 mutex_lock(&group
->notification_mutex
);
122 if (!fsnotify_notify_queue_is_empty(group
))
123 ret
= POLLIN
| POLLRDNORM
;
124 mutex_unlock(&group
->notification_mutex
);
130 * Get an inotify_kernel_event if one exists and is small
131 * enough to fit in "count". Return an error pointer if
134 * Called with the group->notification_mutex held.
136 static struct fsnotify_event
*get_one_event(struct fsnotify_group
*group
,
139 size_t event_size
= sizeof(struct inotify_event
);
140 struct fsnotify_event
*event
;
142 if (fsnotify_notify_queue_is_empty(group
))
145 event
= fsnotify_peek_notify_event(group
);
148 event_size
+= roundup(event
->name_len
+ 1, event_size
);
150 if (event_size
> count
)
151 return ERR_PTR(-EINVAL
);
153 /* held the notification_mutex the whole time, so this is the
154 * same event we peeked above */
155 fsnotify_remove_notify_event(group
);
161 * Copy an event to user space, returning how much we copied.
163 * We already checked that the event size is smaller than the
164 * buffer we had in "get_one_event()" above.
166 static ssize_t
copy_event_to_user(struct fsnotify_group
*group
,
167 struct fsnotify_event
*event
,
170 struct inotify_event inotify_event
;
171 struct fsnotify_event_private_data
*fsn_priv
;
172 struct inotify_event_private_data
*priv
;
173 size_t event_size
= sizeof(struct inotify_event
);
176 /* we get the inotify watch descriptor from the event private data */
177 spin_lock(&event
->lock
);
178 fsn_priv
= fsnotify_remove_priv_from_event(group
, event
);
179 spin_unlock(&event
->lock
);
182 inotify_event
.wd
= -1;
184 priv
= container_of(fsn_priv
, struct inotify_event_private_data
,
185 fsnotify_event_priv_data
);
186 inotify_event
.wd
= priv
->wd
;
187 inotify_free_event_priv(fsn_priv
);
191 * round up event->name_len so it is a multiple of event_size
192 * plus an extra byte for the terminating '\0'.
195 name_len
= roundup(event
->name_len
+ 1, event_size
);
196 inotify_event
.len
= name_len
;
198 inotify_event
.mask
= inotify_mask_to_arg(event
->mask
);
199 inotify_event
.cookie
= event
->sync_cookie
;
201 /* send the main event */
202 if (copy_to_user(buf
, &inotify_event
, event_size
))
208 * fsnotify only stores the pathname, so here we have to send the pathname
209 * and then pad that pathname out to a multiple of sizeof(inotify_event)
210 * with zeros. I get my zeros from the nul_inotify_event.
213 unsigned int len_to_zero
= name_len
- event
->name_len
;
214 /* copy the path name */
215 if (copy_to_user(buf
, event
->file_name
, event
->name_len
))
217 buf
+= event
->name_len
;
219 /* fill userspace with 0's */
220 if (clear_user(buf
, len_to_zero
))
223 event_size
+= name_len
;
229 static ssize_t
inotify_read(struct file
*file
, char __user
*buf
,
230 size_t count
, loff_t
*pos
)
232 struct fsnotify_group
*group
;
233 struct fsnotify_event
*kevent
;
239 group
= file
->private_data
;
242 prepare_to_wait(&group
->notification_waitq
, &wait
, TASK_INTERRUPTIBLE
);
244 mutex_lock(&group
->notification_mutex
);
245 kevent
= get_one_event(group
, count
);
246 mutex_unlock(&group
->notification_mutex
);
249 ret
= PTR_ERR(kevent
);
252 ret
= copy_event_to_user(group
, kevent
, buf
);
253 fsnotify_put_event(kevent
);
262 if (file
->f_flags
& O_NONBLOCK
)
265 if (signal_pending(current
))
274 finish_wait(&group
->notification_waitq
, &wait
);
275 if (start
!= buf
&& ret
!= -EFAULT
)
280 static int inotify_fasync(int fd
, struct file
*file
, int on
)
282 struct fsnotify_group
*group
= file
->private_data
;
284 return fasync_helper(fd
, file
, on
, &group
->inotify_data
.fa
) >= 0 ? 0 : -EIO
;
287 static int inotify_release(struct inode
*ignored
, struct file
*file
)
289 struct fsnotify_group
*group
= file
->private_data
;
290 struct user_struct
*user
= group
->inotify_data
.user
;
292 fsnotify_clear_marks_by_group(group
);
294 /* free this group, matching get was inotify_init->fsnotify_obtain_group */
295 fsnotify_put_group(group
);
297 atomic_dec(&user
->inotify_devs
);
302 static long inotify_ioctl(struct file
*file
, unsigned int cmd
,
305 struct fsnotify_group
*group
;
306 struct fsnotify_event_holder
*holder
;
307 struct fsnotify_event
*event
;
312 group
= file
->private_data
;
313 p
= (void __user
*) arg
;
317 mutex_lock(&group
->notification_mutex
);
318 list_for_each_entry(holder
, &group
->notification_list
, event_list
) {
319 event
= holder
->event
;
320 send_len
+= sizeof(struct inotify_event
);
322 send_len
+= roundup(event
->name_len
+ 1,
323 sizeof(struct inotify_event
));
325 mutex_unlock(&group
->notification_mutex
);
326 ret
= put_user(send_len
, (int __user
*) p
);
333 static const struct file_operations inotify_fops
= {
334 .poll
= inotify_poll
,
335 .read
= inotify_read
,
336 .fasync
= inotify_fasync
,
337 .release
= inotify_release
,
338 .unlocked_ioctl
= inotify_ioctl
,
339 .compat_ioctl
= inotify_ioctl
,
344 * find_inode - resolve a user-given path to a specific inode
346 static int inotify_find_inode(const char __user
*dirname
, struct path
*path
, unsigned flags
)
350 error
= user_path_at(AT_FDCWD
, dirname
, flags
, path
);
353 /* you can only watch an inode if you have read permissions on it */
354 error
= inode_permission(path
->dentry
->d_inode
, MAY_READ
);
360 static int inotify_add_to_idr(struct idr
*idr
, spinlock_t
*idr_lock
,
362 struct inotify_inode_mark_entry
*ientry
)
367 if (unlikely(!idr_pre_get(idr
, GFP_KERNEL
)))
371 ret
= idr_get_new_above(idr
, ientry
, last_wd
+ 1,
373 /* we added the mark to the idr, take a reference */
375 fsnotify_get_mark(&ientry
->fsn_entry
);
376 spin_unlock(idr_lock
);
377 } while (ret
== -EAGAIN
);
382 static struct inotify_inode_mark_entry
*inotify_idr_find_locked(struct fsnotify_group
*group
,
385 struct idr
*idr
= &group
->inotify_data
.idr
;
386 spinlock_t
*idr_lock
= &group
->inotify_data
.idr_lock
;
387 struct inotify_inode_mark_entry
*ientry
;
389 assert_spin_locked(idr_lock
);
391 ientry
= idr_find(idr
, wd
);
393 struct fsnotify_mark_entry
*fsn_entry
= &ientry
->fsn_entry
;
395 fsnotify_get_mark(fsn_entry
);
396 /* One ref for being in the idr, one ref we just took */
397 BUG_ON(atomic_read(&fsn_entry
->refcnt
) < 2);
403 static struct inotify_inode_mark_entry
*inotify_idr_find(struct fsnotify_group
*group
,
406 struct inotify_inode_mark_entry
*ientry
;
407 spinlock_t
*idr_lock
= &group
->inotify_data
.idr_lock
;
410 ientry
= inotify_idr_find_locked(group
, wd
);
411 spin_unlock(idr_lock
);
416 static void do_inotify_remove_from_idr(struct fsnotify_group
*group
,
417 struct inotify_inode_mark_entry
*ientry
)
419 struct idr
*idr
= &group
->inotify_data
.idr
;
420 spinlock_t
*idr_lock
= &group
->inotify_data
.idr_lock
;
423 assert_spin_locked(idr_lock
);
427 /* removed from the idr, drop that ref */
428 fsnotify_put_mark(&ientry
->fsn_entry
);
432 * Remove the mark from the idr (if present) and drop the reference
433 * on the mark because it was in the idr.
435 static void inotify_remove_from_idr(struct fsnotify_group
*group
,
436 struct inotify_inode_mark_entry
*ientry
)
438 spinlock_t
*idr_lock
= &group
->inotify_data
.idr_lock
;
439 struct inotify_inode_mark_entry
*found_ientry
= NULL
;
446 * does this ientry think it is in the idr? we shouldn't get called
450 printk(KERN_WARNING
"%s: ientry=%p ientry->wd=%d ientry->group=%p"
451 " ientry->inode=%p\n", __func__
, ientry
, ientry
->wd
,
452 ientry
->fsn_entry
.group
, ientry
->fsn_entry
.inode
);
457 /* Lets look in the idr to see if we find it */
458 found_ientry
= inotify_idr_find_locked(group
, wd
);
459 if (unlikely(!found_ientry
)) {
460 printk(KERN_WARNING
"%s: ientry=%p ientry->wd=%d ientry->group=%p"
461 " ientry->inode=%p\n", __func__
, ientry
, ientry
->wd
,
462 ientry
->fsn_entry
.group
, ientry
->fsn_entry
.inode
);
468 * We found an entry in the idr at the right wd, but it's
469 * not the entry we were told to remove. eparis seriously
470 * fucked up somewhere.
472 if (unlikely(found_ientry
!= ientry
)) {
474 printk(KERN_WARNING
"%s: ientry=%p ientry->wd=%d ientry->group=%p "
475 "entry->inode=%p found_ientry=%p found_ientry->wd=%d "
476 "found_ientry->group=%p found_ientry->inode=%p\n",
477 __func__
, ientry
, ientry
->wd
, ientry
->fsn_entry
.group
,
478 ientry
->fsn_entry
.inode
, found_ientry
, found_ientry
->wd
,
479 found_ientry
->fsn_entry
.group
,
480 found_ientry
->fsn_entry
.inode
);
485 * One ref for being in the idr
486 * one ref held by the caller trying to kill us
487 * one ref grabbed by inotify_idr_find
489 if (unlikely(atomic_read(&ientry
->fsn_entry
.refcnt
) < 3)) {
490 printk(KERN_WARNING
"%s: ientry=%p ientry->wd=%d ientry->group=%p"
491 " ientry->inode=%p\n", __func__
, ientry
, ientry
->wd
,
492 ientry
->fsn_entry
.group
, ientry
->fsn_entry
.inode
);
493 /* we can't really recover with bad ref cnting.. */
497 do_inotify_remove_from_idr(group
, ientry
);
499 /* match the ref taken by inotify_idr_find_locked() */
501 fsnotify_put_mark(&found_ientry
->fsn_entry
);
503 spin_unlock(idr_lock
);
507 * Send IN_IGNORED for this wd, remove this wd from the idr.
509 void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry
*entry
,
510 struct fsnotify_group
*group
)
512 struct inotify_inode_mark_entry
*ientry
;
513 struct fsnotify_event
*ignored_event
;
514 struct inotify_event_private_data
*event_priv
;
515 struct fsnotify_event_private_data
*fsn_event_priv
;
518 ignored_event
= fsnotify_create_event(NULL
, FS_IN_IGNORED
, NULL
,
519 FSNOTIFY_EVENT_NONE
, NULL
, 0,
524 ientry
= container_of(entry
, struct inotify_inode_mark_entry
, fsn_entry
);
526 event_priv
= kmem_cache_alloc(event_priv_cachep
, GFP_NOFS
);
527 if (unlikely(!event_priv
))
528 goto skip_send_ignore
;
530 fsn_event_priv
= &event_priv
->fsnotify_event_priv_data
;
532 fsn_event_priv
->group
= group
;
533 event_priv
->wd
= ientry
->wd
;
535 ret
= fsnotify_add_notify_event(group
, ignored_event
, fsn_event_priv
);
537 inotify_free_event_priv(fsn_event_priv
);
541 /* matches the reference taken when the event was created */
542 fsnotify_put_event(ignored_event
);
544 /* remove this entry from the idr */
545 inotify_remove_from_idr(group
, ientry
);
547 atomic_dec(&group
->inotify_data
.user
->inotify_watches
);
550 /* ding dong the mark is dead */
551 static void inotify_free_mark(struct fsnotify_mark_entry
*entry
)
553 struct inotify_inode_mark_entry
*ientry
= (struct inotify_inode_mark_entry
*)entry
;
555 kmem_cache_free(inotify_inode_mark_cachep
, ientry
);
558 static int inotify_update_existing_watch(struct fsnotify_group
*group
,
562 struct fsnotify_mark_entry
*entry
;
563 struct inotify_inode_mark_entry
*ientry
;
564 __u32 old_mask
, new_mask
;
566 int add
= (arg
& IN_MASK_ADD
);
569 /* don't allow invalid bits: we don't want flags set */
570 mask
= inotify_arg_to_mask(arg
);
574 spin_lock(&inode
->i_lock
);
575 entry
= fsnotify_find_mark_entry(group
, inode
);
576 spin_unlock(&inode
->i_lock
);
580 ientry
= container_of(entry
, struct inotify_inode_mark_entry
, fsn_entry
);
582 spin_lock(&entry
->lock
);
584 old_mask
= entry
->mask
;
587 new_mask
= entry
->mask
;
590 new_mask
= entry
->mask
;
593 spin_unlock(&entry
->lock
);
595 if (old_mask
!= new_mask
) {
596 /* more bits in old than in new? */
597 int dropped
= (old_mask
& ~new_mask
);
598 /* more bits in this entry than the inode's mask? */
599 int do_inode
= (new_mask
& ~inode
->i_fsnotify_mask
);
600 /* more bits in this entry than the group? */
601 int do_group
= (new_mask
& ~group
->mask
);
603 /* update the inode with this new entry */
604 if (dropped
|| do_inode
)
605 fsnotify_recalc_inode_mask(inode
);
607 /* update the group mask with the new mask */
608 if (dropped
|| do_group
)
609 fsnotify_recalc_group_mask(group
);
615 /* match the get from fsnotify_find_mark_entry() */
616 fsnotify_put_mark(entry
);
621 static int inotify_new_watch(struct fsnotify_group
*group
,
625 struct inotify_inode_mark_entry
*tmp_ientry
;
628 struct idr
*idr
= &group
->inotify_data
.idr
;
629 spinlock_t
*idr_lock
= &group
->inotify_data
.idr_lock
;
631 /* don't allow invalid bits: we don't want flags set */
632 mask
= inotify_arg_to_mask(arg
);
636 tmp_ientry
= kmem_cache_alloc(inotify_inode_mark_cachep
, GFP_KERNEL
);
637 if (unlikely(!tmp_ientry
))
640 fsnotify_init_mark(&tmp_ientry
->fsn_entry
, inotify_free_mark
);
641 tmp_ientry
->fsn_entry
.mask
= mask
;
645 if (atomic_read(&group
->inotify_data
.user
->inotify_watches
) >= inotify_max_user_watches
)
648 ret
= inotify_add_to_idr(idr
, idr_lock
, group
->inotify_data
.last_wd
,
653 /* we are on the idr, now get on the inode */
654 ret
= fsnotify_add_mark(&tmp_ientry
->fsn_entry
, group
, inode
, 0);
656 /* we failed to get on the inode, get off the idr */
657 inotify_remove_from_idr(group
, tmp_ientry
);
661 /* update the idr hint, who cares about races, it's just a hint */
662 group
->inotify_data
.last_wd
= tmp_ientry
->wd
;
664 /* increment the number of watches the user has */
665 atomic_inc(&group
->inotify_data
.user
->inotify_watches
);
667 /* return the watch descriptor for this new entry */
668 ret
= tmp_ientry
->wd
;
670 /* if this mark added a new event update the group mask */
671 if (mask
& ~group
->mask
)
672 fsnotify_recalc_group_mask(group
);
675 /* match the ref from fsnotify_init_markentry() */
676 fsnotify_put_mark(&tmp_ientry
->fsn_entry
);
681 static int inotify_update_watch(struct fsnotify_group
*group
, struct inode
*inode
, u32 arg
)
686 /* try to update and existing watch with the new arg */
687 ret
= inotify_update_existing_watch(group
, inode
, arg
);
688 /* no mark present, try to add a new one */
690 ret
= inotify_new_watch(group
, inode
, arg
);
692 * inotify_new_watch could race with another thread which did an
693 * inotify_new_watch between the update_existing and the add watch
694 * here, go back and try to update an existing mark again.
702 static struct fsnotify_group
*inotify_new_group(struct user_struct
*user
, unsigned int max_events
)
704 struct fsnotify_group
*group
;
705 unsigned int grp_num
;
707 /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
708 grp_num
= (INOTIFY_GROUP_NUM
- atomic_inc_return(&inotify_grp_num
));
709 group
= fsnotify_obtain_group(grp_num
, 0, &inotify_fsnotify_ops
);
713 group
->max_events
= max_events
;
715 spin_lock_init(&group
->inotify_data
.idr_lock
);
716 idr_init(&group
->inotify_data
.idr
);
717 group
->inotify_data
.last_wd
= 0;
718 group
->inotify_data
.user
= user
;
719 group
->inotify_data
.fa
= NULL
;
725 /* inotify syscalls */
726 SYSCALL_DEFINE1(inotify_init1
, int, flags
)
728 struct fsnotify_group
*group
;
729 struct user_struct
*user
;
732 /* Check the IN_* constants for consistency. */
733 BUILD_BUG_ON(IN_CLOEXEC
!= O_CLOEXEC
);
734 BUILD_BUG_ON(IN_NONBLOCK
!= O_NONBLOCK
);
736 if (flags
& ~(IN_CLOEXEC
| IN_NONBLOCK
))
739 user
= get_current_user();
740 if (unlikely(atomic_read(&user
->inotify_devs
) >=
741 inotify_max_user_instances
)) {
746 /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
747 group
= inotify_new_group(user
, inotify_max_queued_events
);
749 ret
= PTR_ERR(group
);
753 atomic_inc(&user
->inotify_devs
);
755 ret
= anon_inode_getfd("inotify", &inotify_fops
, group
,
760 atomic_dec(&user
->inotify_devs
);
766 SYSCALL_DEFINE0(inotify_init
)
768 return sys_inotify_init1(0);
771 SYSCALL_DEFINE3(inotify_add_watch
, int, fd
, const char __user
*, pathname
,
774 struct fsnotify_group
*group
;
778 int ret
, fput_needed
;
781 filp
= fget_light(fd
, &fput_needed
);
785 /* verify that this is indeed an inotify instance */
786 if (unlikely(filp
->f_op
!= &inotify_fops
)) {
791 if (!(mask
& IN_DONT_FOLLOW
))
792 flags
|= LOOKUP_FOLLOW
;
793 if (mask
& IN_ONLYDIR
)
794 flags
|= LOOKUP_DIRECTORY
;
796 ret
= inotify_find_inode(pathname
, &path
, flags
);
800 /* inode held in place by reference to path; group by fget on fd */
801 inode
= path
.dentry
->d_inode
;
802 group
= filp
->private_data
;
804 /* create/update an inode mark */
805 ret
= inotify_update_watch(group
, inode
, mask
);
808 fput_light(filp
, fput_needed
);
812 SYSCALL_DEFINE2(inotify_rm_watch
, int, fd
, __s32
, wd
)
814 struct fsnotify_group
*group
;
815 struct inotify_inode_mark_entry
*ientry
;
817 int ret
= 0, fput_needed
;
819 filp
= fget_light(fd
, &fput_needed
);
823 /* verify that this is indeed an inotify instance */
825 if (unlikely(filp
->f_op
!= &inotify_fops
))
828 group
= filp
->private_data
;
831 ientry
= inotify_idr_find(group
, wd
);
832 if (unlikely(!ientry
))
837 fsnotify_destroy_mark_by_entry(&ientry
->fsn_entry
);
839 /* match ref taken by inotify_idr_find */
840 fsnotify_put_mark(&ientry
->fsn_entry
);
843 fput_light(filp
, fput_needed
);
848 * inotify_user_setup - Our initialization function. Note that we cannnot return
849 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
850 * must result in panic().
852 static int __init
inotify_user_setup(void)
854 inotify_inode_mark_cachep
= KMEM_CACHE(inotify_inode_mark_entry
, SLAB_PANIC
);
855 event_priv_cachep
= KMEM_CACHE(inotify_event_private_data
, SLAB_PANIC
);
857 inotify_max_queued_events
= 16384;
858 inotify_max_user_instances
= 128;
859 inotify_max_user_watches
= 8192;
863 module_init(inotify_user_setup
);