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/magic.h> /* superblock magic number */
33 #include <linux/mount.h> /* mntget */
34 #include <linux/namei.h> /* LOOKUP_FOLLOW */
35 #include <linux/path.h> /* struct path */
36 #include <linux/sched.h> /* struct user */
37 #include <linux/slab.h> /* struct kmem_cache */
38 #include <linux/syscalls.h>
39 #include <linux/types.h>
40 #include <linux/uaccess.h>
41 #include <linux/poll.h>
42 #include <linux/wait.h>
46 #include <asm/ioctls.h>
48 static struct vfsmount
*inotify_mnt __read_mostly
;
50 /* this just sits here and wastes global memory. used to just pad userspace messages with zeros */
51 static struct inotify_event nul_inotify_event
;
53 /* these are configurable via /proc/sys/fs/inotify/ */
54 static int inotify_max_user_instances __read_mostly
;
55 static int inotify_max_queued_events __read_mostly
;
56 int inotify_max_user_watches __read_mostly
;
58 static struct kmem_cache
*inotify_inode_mark_cachep __read_mostly
;
59 struct kmem_cache
*event_priv_cachep __read_mostly
;
60 static struct fsnotify_event
*inotify_ignored_event
;
63 * When inotify registers a new group it increments this and uses that
64 * value as an offset to set the fsnotify group "name" and priority.
66 static atomic_t inotify_grp_num
;
70 #include <linux/sysctl.h>
74 ctl_table inotify_table
[] = {
76 .ctl_name
= INOTIFY_MAX_USER_INSTANCES
,
77 .procname
= "max_user_instances",
78 .data
= &inotify_max_user_instances
,
79 .maxlen
= sizeof(int),
81 .proc_handler
= &proc_dointvec_minmax
,
82 .strategy
= &sysctl_intvec
,
86 .ctl_name
= INOTIFY_MAX_USER_WATCHES
,
87 .procname
= "max_user_watches",
88 .data
= &inotify_max_user_watches
,
89 .maxlen
= sizeof(int),
91 .proc_handler
= &proc_dointvec_minmax
,
92 .strategy
= &sysctl_intvec
,
96 .ctl_name
= INOTIFY_MAX_QUEUED_EVENTS
,
97 .procname
= "max_queued_events",
98 .data
= &inotify_max_queued_events
,
99 .maxlen
= sizeof(int),
101 .proc_handler
= &proc_dointvec_minmax
,
102 .strategy
= &sysctl_intvec
,
107 #endif /* CONFIG_SYSCTL */
109 static inline __u32
inotify_arg_to_mask(u32 arg
)
113 /* everything should accept their own ignored and cares about children */
114 mask
= (FS_IN_IGNORED
| FS_EVENT_ON_CHILD
);
116 /* mask off the flags used to open the fd */
117 mask
|= (arg
& (IN_ALL_EVENTS
| IN_ONESHOT
));
122 static inline u32
inotify_mask_to_arg(__u32 mask
)
124 return mask
& (IN_ALL_EVENTS
| IN_ISDIR
| IN_UNMOUNT
| IN_IGNORED
|
128 /* intofiy userspace file descriptor functions */
129 static unsigned int inotify_poll(struct file
*file
, poll_table
*wait
)
131 struct fsnotify_group
*group
= file
->private_data
;
134 poll_wait(file
, &group
->notification_waitq
, wait
);
135 mutex_lock(&group
->notification_mutex
);
136 if (!fsnotify_notify_queue_is_empty(group
))
137 ret
= POLLIN
| POLLRDNORM
;
138 mutex_unlock(&group
->notification_mutex
);
144 * Get an inotify_kernel_event if one exists and is small
145 * enough to fit in "count". Return an error pointer if
148 * Called with the group->notification_mutex held.
150 static struct fsnotify_event
*get_one_event(struct fsnotify_group
*group
,
153 size_t event_size
= sizeof(struct inotify_event
);
154 struct fsnotify_event
*event
;
156 if (fsnotify_notify_queue_is_empty(group
))
159 event
= fsnotify_peek_notify_event(group
);
161 event_size
+= roundup(event
->name_len
, event_size
);
163 if (event_size
> count
)
164 return ERR_PTR(-EINVAL
);
166 /* held the notification_mutex the whole time, so this is the
167 * same event we peeked above */
168 fsnotify_remove_notify_event(group
);
174 * Copy an event to user space, returning how much we copied.
176 * We already checked that the event size is smaller than the
177 * buffer we had in "get_one_event()" above.
179 static ssize_t
copy_event_to_user(struct fsnotify_group
*group
,
180 struct fsnotify_event
*event
,
183 struct inotify_event inotify_event
;
184 struct fsnotify_event_private_data
*fsn_priv
;
185 struct inotify_event_private_data
*priv
;
186 size_t event_size
= sizeof(struct inotify_event
);
189 /* we get the inotify watch descriptor from the event private data */
190 spin_lock(&event
->lock
);
191 fsn_priv
= fsnotify_remove_priv_from_event(group
, event
);
192 spin_unlock(&event
->lock
);
195 inotify_event
.wd
= -1;
197 priv
= container_of(fsn_priv
, struct inotify_event_private_data
,
198 fsnotify_event_priv_data
);
199 inotify_event
.wd
= priv
->wd
;
200 inotify_free_event_priv(fsn_priv
);
203 /* round up event->name_len so it is a multiple of event_size */
204 name_len
= roundup(event
->name_len
, event_size
);
205 inotify_event
.len
= name_len
;
207 inotify_event
.mask
= inotify_mask_to_arg(event
->mask
);
208 inotify_event
.cookie
= event
->sync_cookie
;
210 /* send the main event */
211 if (copy_to_user(buf
, &inotify_event
, event_size
))
217 * fsnotify only stores the pathname, so here we have to send the pathname
218 * and then pad that pathname out to a multiple of sizeof(inotify_event)
219 * with zeros. I get my zeros from the nul_inotify_event.
222 unsigned int len_to_zero
= name_len
- event
->name_len
;
223 /* copy the path name */
224 if (copy_to_user(buf
, event
->file_name
, event
->name_len
))
226 buf
+= event
->name_len
;
228 /* fill userspace with 0's from nul_inotify_event */
229 if (copy_to_user(buf
, &nul_inotify_event
, len_to_zero
))
232 event_size
+= name_len
;
238 static ssize_t
inotify_read(struct file
*file
, char __user
*buf
,
239 size_t count
, loff_t
*pos
)
241 struct fsnotify_group
*group
;
242 struct fsnotify_event
*kevent
;
248 group
= file
->private_data
;
251 prepare_to_wait(&group
->notification_waitq
, &wait
, TASK_INTERRUPTIBLE
);
253 mutex_lock(&group
->notification_mutex
);
254 kevent
= get_one_event(group
, count
);
255 mutex_unlock(&group
->notification_mutex
);
258 ret
= PTR_ERR(kevent
);
261 ret
= copy_event_to_user(group
, kevent
, buf
);
262 fsnotify_put_event(kevent
);
271 if (file
->f_flags
& O_NONBLOCK
)
274 if (signal_pending(current
))
283 finish_wait(&group
->notification_waitq
, &wait
);
284 if (start
!= buf
&& ret
!= -EFAULT
)
289 static int inotify_fasync(int fd
, struct file
*file
, int on
)
291 struct fsnotify_group
*group
= file
->private_data
;
293 return fasync_helper(fd
, file
, on
, &group
->inotify_data
.fa
) >= 0 ? 0 : -EIO
;
296 static int inotify_release(struct inode
*ignored
, struct file
*file
)
298 struct fsnotify_group
*group
= file
->private_data
;
299 struct user_struct
*user
= group
->inotify_data
.user
;
301 fsnotify_clear_marks_by_group(group
);
303 /* free this group, matching get was inotify_init->fsnotify_obtain_group */
304 fsnotify_put_group(group
);
306 atomic_dec(&user
->inotify_devs
);
311 static long inotify_ioctl(struct file
*file
, unsigned int cmd
,
314 struct fsnotify_group
*group
;
315 struct fsnotify_event_holder
*holder
;
316 struct fsnotify_event
*event
;
321 group
= file
->private_data
;
322 p
= (void __user
*) arg
;
326 mutex_lock(&group
->notification_mutex
);
327 list_for_each_entry(holder
, &group
->notification_list
, event_list
) {
328 event
= holder
->event
;
329 send_len
+= sizeof(struct inotify_event
);
330 send_len
+= roundup(event
->name_len
,
331 sizeof(struct inotify_event
));
333 mutex_unlock(&group
->notification_mutex
);
334 ret
= put_user(send_len
, (int __user
*) p
);
341 static const struct file_operations inotify_fops
= {
342 .poll
= inotify_poll
,
343 .read
= inotify_read
,
344 .fasync
= inotify_fasync
,
345 .release
= inotify_release
,
346 .unlocked_ioctl
= inotify_ioctl
,
347 .compat_ioctl
= inotify_ioctl
,
352 * find_inode - resolve a user-given path to a specific inode
354 static int inotify_find_inode(const char __user
*dirname
, struct path
*path
, unsigned flags
)
358 error
= user_path_at(AT_FDCWD
, dirname
, flags
, path
);
361 /* you can only watch an inode if you have read permissions on it */
362 error
= inode_permission(path
->dentry
->d_inode
, MAY_READ
);
369 * Send IN_IGNORED for this wd, remove this wd from the idr, and drop the
370 * internal reference help on the mark because it is in the idr.
372 void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry
*entry
,
373 struct fsnotify_group
*group
)
375 struct inotify_inode_mark_entry
*ientry
;
376 struct inotify_event_private_data
*event_priv
;
377 struct fsnotify_event_private_data
*fsn_event_priv
;
380 ientry
= container_of(entry
, struct inotify_inode_mark_entry
, fsn_entry
);
382 event_priv
= kmem_cache_alloc(event_priv_cachep
, GFP_KERNEL
);
383 if (unlikely(!event_priv
))
384 goto skip_send_ignore
;
386 fsn_event_priv
= &event_priv
->fsnotify_event_priv_data
;
388 fsn_event_priv
->group
= group
;
389 event_priv
->wd
= ientry
->wd
;
391 fsnotify_add_notify_event(group
, inotify_ignored_event
, fsn_event_priv
);
393 /* did the private data get added? */
394 if (list_empty(&fsn_event_priv
->event_list
))
395 inotify_free_event_priv(fsn_event_priv
);
399 /* remove this entry from the idr */
400 spin_lock(&group
->inotify_data
.idr_lock
);
401 idr
= &group
->inotify_data
.idr
;
402 idr_remove(idr
, ientry
->wd
);
403 spin_unlock(&group
->inotify_data
.idr_lock
);
405 /* removed from idr, drop that reference */
406 fsnotify_put_mark(entry
);
408 atomic_dec(&group
->inotify_data
.user
->inotify_watches
);
411 /* ding dong the mark is dead */
412 static void inotify_free_mark(struct fsnotify_mark_entry
*entry
)
414 struct inotify_inode_mark_entry
*ientry
= (struct inotify_inode_mark_entry
*)entry
;
416 kmem_cache_free(inotify_inode_mark_cachep
, ientry
);
419 static int inotify_update_watch(struct fsnotify_group
*group
, struct inode
*inode
, u32 arg
)
421 struct fsnotify_mark_entry
*entry
= NULL
;
422 struct inotify_inode_mark_entry
*ientry
;
424 int add
= (arg
& IN_MASK_ADD
);
426 __u32 old_mask
, new_mask
;
428 /* don't allow invalid bits: we don't want flags set */
429 mask
= inotify_arg_to_mask(arg
);
433 ientry
= kmem_cache_alloc(inotify_inode_mark_cachep
, GFP_KERNEL
);
434 if (unlikely(!ientry
))
436 /* we set the mask at the end after attaching it */
437 fsnotify_init_mark(&ientry
->fsn_entry
, inotify_free_mark
);
441 spin_lock(&inode
->i_lock
);
442 entry
= fsnotify_find_mark_entry(group
, inode
);
443 spin_unlock(&inode
->i_lock
);
445 kmem_cache_free(inotify_inode_mark_cachep
, ientry
);
446 ientry
= container_of(entry
, struct inotify_inode_mark_entry
, fsn_entry
);
448 if (atomic_read(&group
->inotify_data
.user
->inotify_watches
) >= inotify_max_user_watches
) {
453 ret
= fsnotify_add_mark(&ientry
->fsn_entry
, group
, inode
);
459 entry
= &ientry
->fsn_entry
;
462 if (unlikely(!idr_pre_get(&group
->inotify_data
.idr
, GFP_KERNEL
)))
465 spin_lock(&group
->inotify_data
.idr_lock
);
466 /* if entry is added to the idr we keep the reference obtained
467 * through fsnotify_mark_add. remember to drop this reference
468 * when entry is removed from idr */
469 ret
= idr_get_new_above(&group
->inotify_data
.idr
, entry
,
470 ++group
->inotify_data
.last_wd
,
472 spin_unlock(&group
->inotify_data
.idr_lock
);
478 atomic_inc(&group
->inotify_data
.user
->inotify_watches
);
481 spin_lock(&entry
->lock
);
483 old_mask
= entry
->mask
;
486 new_mask
= entry
->mask
;
489 new_mask
= entry
->mask
;
492 spin_unlock(&entry
->lock
);
494 if (old_mask
!= new_mask
) {
495 /* more bits in old than in new? */
496 int dropped
= (old_mask
& ~new_mask
);
497 /* more bits in this entry than the inode's mask? */
498 int do_inode
= (new_mask
& ~inode
->i_fsnotify_mask
);
499 /* more bits in this entry than the group? */
500 int do_group
= (new_mask
& ~group
->mask
);
502 /* update the inode with this new entry */
503 if (dropped
|| do_inode
)
504 fsnotify_recalc_inode_mask(inode
);
506 /* update the group mask with the new mask */
507 if (dropped
|| do_group
)
508 fsnotify_recalc_group_mask(group
);
514 /* see this isn't supposed to happen, just kill the watch */
516 fsnotify_destroy_mark_by_entry(entry
);
517 fsnotify_put_mark(entry
);
522 static struct fsnotify_group
*inotify_new_group(struct user_struct
*user
, unsigned int max_events
)
524 struct fsnotify_group
*group
;
525 unsigned int grp_num
;
527 /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
528 grp_num
= (INOTIFY_GROUP_NUM
- atomic_inc_return(&inotify_grp_num
));
529 group
= fsnotify_obtain_group(grp_num
, 0, &inotify_fsnotify_ops
);
533 group
->max_events
= max_events
;
535 spin_lock_init(&group
->inotify_data
.idr_lock
);
536 idr_init(&group
->inotify_data
.idr
);
537 group
->inotify_data
.last_wd
= 0;
538 group
->inotify_data
.user
= user
;
539 group
->inotify_data
.fa
= NULL
;
545 /* inotify syscalls */
546 SYSCALL_DEFINE1(inotify_init1
, int, flags
)
548 struct fsnotify_group
*group
;
549 struct user_struct
*user
;
553 /* Check the IN_* constants for consistency. */
554 BUILD_BUG_ON(IN_CLOEXEC
!= O_CLOEXEC
);
555 BUILD_BUG_ON(IN_NONBLOCK
!= O_NONBLOCK
);
557 if (flags
& ~(IN_CLOEXEC
| IN_NONBLOCK
))
560 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
564 filp
= get_empty_filp();
570 user
= get_current_user();
571 if (unlikely(atomic_read(&user
->inotify_devs
) >=
572 inotify_max_user_instances
)) {
577 /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
578 group
= inotify_new_group(user
, inotify_max_queued_events
);
580 ret
= PTR_ERR(group
);
584 filp
->f_op
= &inotify_fops
;
585 filp
->f_path
.mnt
= mntget(inotify_mnt
);
586 filp
->f_path
.dentry
= dget(inotify_mnt
->mnt_root
);
587 filp
->f_mapping
= filp
->f_path
.dentry
->d_inode
->i_mapping
;
588 filp
->f_mode
= FMODE_READ
;
589 filp
->f_flags
= O_RDONLY
| (flags
& O_NONBLOCK
);
590 filp
->private_data
= group
;
592 atomic_inc(&user
->inotify_devs
);
594 fd_install(fd
, filp
);
606 SYSCALL_DEFINE0(inotify_init
)
608 return sys_inotify_init1(0);
611 SYSCALL_DEFINE3(inotify_add_watch
, int, fd
, const char __user
*, pathname
,
614 struct fsnotify_group
*group
;
618 int ret
, fput_needed
;
621 filp
= fget_light(fd
, &fput_needed
);
625 /* verify that this is indeed an inotify instance */
626 if (unlikely(filp
->f_op
!= &inotify_fops
)) {
631 if (!(mask
& IN_DONT_FOLLOW
))
632 flags
|= LOOKUP_FOLLOW
;
633 if (mask
& IN_ONLYDIR
)
634 flags
|= LOOKUP_DIRECTORY
;
636 ret
= inotify_find_inode(pathname
, &path
, flags
);
640 /* inode held in place by reference to path; group by fget on fd */
641 inode
= path
.dentry
->d_inode
;
642 group
= filp
->private_data
;
644 /* create/update an inode mark */
645 ret
= inotify_update_watch(group
, inode
, mask
);
647 goto path_put_and_out
;
652 fput_light(filp
, fput_needed
);
656 SYSCALL_DEFINE2(inotify_rm_watch
, int, fd
, __s32
, wd
)
658 struct fsnotify_group
*group
;
659 struct fsnotify_mark_entry
*entry
;
661 int ret
= 0, fput_needed
;
663 filp
= fget_light(fd
, &fput_needed
);
667 /* verify that this is indeed an inotify instance */
668 if (unlikely(filp
->f_op
!= &inotify_fops
)) {
673 group
= filp
->private_data
;
675 spin_lock(&group
->inotify_data
.idr_lock
);
676 entry
= idr_find(&group
->inotify_data
.idr
, wd
);
677 if (unlikely(!entry
)) {
678 spin_unlock(&group
->inotify_data
.idr_lock
);
682 fsnotify_get_mark(entry
);
683 spin_unlock(&group
->inotify_data
.idr_lock
);
685 fsnotify_destroy_mark_by_entry(entry
);
686 fsnotify_put_mark(entry
);
689 fput_light(filp
, fput_needed
);
694 inotify_get_sb(struct file_system_type
*fs_type
, int flags
,
695 const char *dev_name
, void *data
, struct vfsmount
*mnt
)
697 return get_sb_pseudo(fs_type
, "inotify", NULL
,
698 INOTIFYFS_SUPER_MAGIC
, mnt
);
701 static struct file_system_type inotify_fs_type
= {
703 .get_sb
= inotify_get_sb
,
704 .kill_sb
= kill_anon_super
,
708 * inotify_user_setup - Our initialization function. Note that we cannnot return
709 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
710 * must result in panic().
712 static int __init
inotify_user_setup(void)
716 ret
= register_filesystem(&inotify_fs_type
);
718 panic("inotify: register_filesystem returned %d!\n", ret
);
720 inotify_mnt
= kern_mount(&inotify_fs_type
);
721 if (IS_ERR(inotify_mnt
))
722 panic("inotify: kern_mount ret %ld!\n", PTR_ERR(inotify_mnt
));
724 inotify_inode_mark_cachep
= KMEM_CACHE(inotify_inode_mark_entry
, SLAB_PANIC
);
725 event_priv_cachep
= KMEM_CACHE(inotify_event_private_data
, SLAB_PANIC
);
726 inotify_ignored_event
= fsnotify_create_event(NULL
, FS_IN_IGNORED
, NULL
, FSNOTIFY_EVENT_NONE
, NULL
, 0);
727 if (!inotify_ignored_event
)
728 panic("unable to allocate the inotify ignored event\n");
730 inotify_max_queued_events
= 16384;
731 inotify_max_user_instances
= 128;
732 inotify_max_user_watches
= 8192;
736 module_init(inotify_user_setup
);