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Linux/fs/notify/inotify/inotify_user.c

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  1 /*
  2  * fs/inotify_user.c - inotify support for userspace
  3  *
  4  * Authors:
  5  *      John McCutchan  <ttb@tentacle.dhs.org>
  6  *      Robert Love     <rml@novell.com>
  7  *
  8  * Copyright (C) 2005 John McCutchan
  9  * Copyright 2006 Hewlett-Packard Development Company, L.P.
 10  *
 11  * Copyright (C) 2009 Eric Paris <Red Hat Inc>
 12  * inotify was largely rewriten to make use of the fsnotify infrastructure
 13  *
 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
 17  * later version.
 18  *
 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.
 23  */
 24 
 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>
 41 
 42 #include "inotify.h"
 43 #include "../fdinfo.h"
 44 
 45 #include <asm/ioctls.h>
 46 
 47 /* these are configurable via /proc/sys/fs/inotify/ */
 48 static int inotify_max_user_instances __read_mostly;
 49 static int inotify_max_queued_events __read_mostly;
 50 static int inotify_max_user_watches __read_mostly;
 51 
 52 static struct kmem_cache *inotify_inode_mark_cachep __read_mostly;
 53 struct kmem_cache *event_priv_cachep __read_mostly;
 54 
 55 #ifdef CONFIG_SYSCTL
 56 
 57 #include <linux/sysctl.h>
 58 
 59 static int zero;
 60 
 61 ctl_table inotify_table[] = {
 62         {
 63                 .procname       = "max_user_instances",
 64                 .data           = &inotify_max_user_instances,
 65                 .maxlen         = sizeof(int),
 66                 .mode           = 0644,
 67                 .proc_handler   = proc_dointvec_minmax,
 68                 .extra1         = &zero,
 69         },
 70         {
 71                 .procname       = "max_user_watches",
 72                 .data           = &inotify_max_user_watches,
 73                 .maxlen         = sizeof(int),
 74                 .mode           = 0644,
 75                 .proc_handler   = proc_dointvec_minmax,
 76                 .extra1         = &zero,
 77         },
 78         {
 79                 .procname       = "max_queued_events",
 80                 .data           = &inotify_max_queued_events,
 81                 .maxlen         = sizeof(int),
 82                 .mode           = 0644,
 83                 .proc_handler   = proc_dointvec_minmax,
 84                 .extra1         = &zero
 85         },
 86         { }
 87 };
 88 #endif /* CONFIG_SYSCTL */
 89 
 90 static inline __u32 inotify_arg_to_mask(u32 arg)
 91 {
 92         __u32 mask;
 93 
 94         /*
 95          * everything should accept their own ignored, cares about children,
 96          * and should receive events when the inode is unmounted
 97          */
 98         mask = (FS_IN_IGNORED | FS_EVENT_ON_CHILD | FS_UNMOUNT);
 99 
100         /* mask off the flags used to open the fd */
101         mask |= (arg & (IN_ALL_EVENTS | IN_ONESHOT | IN_EXCL_UNLINK));
102 
103         return mask;
104 }
105 
106 static inline u32 inotify_mask_to_arg(__u32 mask)
107 {
108         return mask & (IN_ALL_EVENTS | IN_ISDIR | IN_UNMOUNT | IN_IGNORED |
109                        IN_Q_OVERFLOW);
110 }
111 
112 /* intofiy userspace file descriptor functions */
113 static unsigned int inotify_poll(struct file *file, poll_table *wait)
114 {
115         struct fsnotify_group *group = file->private_data;
116         int ret = 0;
117 
118         poll_wait(file, &group->notification_waitq, wait);
119         mutex_lock(&group->notification_mutex);
120         if (!fsnotify_notify_queue_is_empty(group))
121                 ret = POLLIN | POLLRDNORM;
122         mutex_unlock(&group->notification_mutex);
123 
124         return ret;
125 }
126 
127 /*
128  * Get an inotify_kernel_event if one exists and is small
129  * enough to fit in "count". Return an error pointer if
130  * not large enough.
131  *
132  * Called with the group->notification_mutex held.
133  */
134 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
135                                             size_t count)
136 {
137         size_t event_size = sizeof(struct inotify_event);
138         struct fsnotify_event *event;
139 
140         if (fsnotify_notify_queue_is_empty(group))
141                 return NULL;
142 
143         event = fsnotify_peek_notify_event(group);
144 
145         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
146 
147         if (event->name_len)
148                 event_size += roundup(event->name_len + 1, event_size);
149 
150         if (event_size > count)
151                 return ERR_PTR(-EINVAL);
152 
153         /* held the notification_mutex the whole time, so this is the
154          * same event we peeked above */
155         fsnotify_remove_notify_event(group);
156 
157         return event;
158 }
159 
160 /*
161  * Copy an event to user space, returning how much we copied.
162  *
163  * We already checked that the event size is smaller than the
164  * buffer we had in "get_one_event()" above.
165  */
166 static ssize_t copy_event_to_user(struct fsnotify_group *group,
167                                   struct fsnotify_event *event,
168                                   char __user *buf)
169 {
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);
174         size_t name_len = 0;
175 
176         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
177 
178         /* we get the inotify watch descriptor from the event private data */
179         spin_lock(&event->lock);
180         fsn_priv = fsnotify_remove_priv_from_event(group, event);
181         spin_unlock(&event->lock);
182 
183         if (!fsn_priv)
184                 inotify_event.wd = -1;
185         else {
186                 priv = container_of(fsn_priv, struct inotify_event_private_data,
187                                     fsnotify_event_priv_data);
188                 inotify_event.wd = priv->wd;
189                 inotify_free_event_priv(fsn_priv);
190         }
191 
192         /*
193          * round up event->name_len so it is a multiple of event_size
194          * plus an extra byte for the terminating '\0'.
195          */
196         if (event->name_len)
197                 name_len = roundup(event->name_len + 1, event_size);
198         inotify_event.len = name_len;
199 
200         inotify_event.mask = inotify_mask_to_arg(event->mask);
201         inotify_event.cookie = event->sync_cookie;
202 
203         /* send the main event */
204         if (copy_to_user(buf, &inotify_event, event_size))
205                 return -EFAULT;
206 
207         buf += event_size;
208 
209         /*
210          * fsnotify only stores the pathname, so here we have to send the pathname
211          * and then pad that pathname out to a multiple of sizeof(inotify_event)
212          * with zeros.  I get my zeros from the nul_inotify_event.
213          */
214         if (name_len) {
215                 unsigned int len_to_zero = name_len - event->name_len;
216                 /* copy the path name */
217                 if (copy_to_user(buf, event->file_name, event->name_len))
218                         return -EFAULT;
219                 buf += event->name_len;
220 
221                 /* fill userspace with 0's */
222                 if (clear_user(buf, len_to_zero))
223                         return -EFAULT;
224                 buf += len_to_zero;
225                 event_size += name_len;
226         }
227 
228         return event_size;
229 }
230 
231 static ssize_t inotify_read(struct file *file, char __user *buf,
232                             size_t count, loff_t *pos)
233 {
234         struct fsnotify_group *group;
235         struct fsnotify_event *kevent;
236         char __user *start;
237         int ret;
238         DEFINE_WAIT(wait);
239 
240         start = buf;
241         group = file->private_data;
242 
243         while (1) {
244                 prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
245 
246                 mutex_lock(&group->notification_mutex);
247                 kevent = get_one_event(group, count);
248                 mutex_unlock(&group->notification_mutex);
249 
250                 pr_debug("%s: group=%p kevent=%p\n", __func__, group, kevent);
251 
252                 if (kevent) {
253                         ret = PTR_ERR(kevent);
254                         if (IS_ERR(kevent))
255                                 break;
256                         ret = copy_event_to_user(group, kevent, buf);
257                         fsnotify_put_event(kevent);
258                         if (ret < 0)
259                                 break;
260                         buf += ret;
261                         count -= ret;
262                         continue;
263                 }
264 
265                 ret = -EAGAIN;
266                 if (file->f_flags & O_NONBLOCK)
267                         break;
268                 ret = -ERESTARTSYS;
269                 if (signal_pending(current))
270                         break;
271 
272                 if (start != buf)
273                         break;
274 
275                 schedule();
276         }
277 
278         finish_wait(&group->notification_waitq, &wait);
279         if (start != buf && ret != -EFAULT)
280                 ret = buf - start;
281         return ret;
282 }
283 
284 static int inotify_release(struct inode *ignored, struct file *file)
285 {
286         struct fsnotify_group *group = file->private_data;
287 
288         pr_debug("%s: group=%p\n", __func__, group);
289 
290         /* free this group, matching get was inotify_init->fsnotify_obtain_group */
291         fsnotify_destroy_group(group);
292 
293         return 0;
294 }
295 
296 static long inotify_ioctl(struct file *file, unsigned int cmd,
297                           unsigned long arg)
298 {
299         struct fsnotify_group *group;
300         struct fsnotify_event_holder *holder;
301         struct fsnotify_event *event;
302         void __user *p;
303         int ret = -ENOTTY;
304         size_t send_len = 0;
305 
306         group = file->private_data;
307         p = (void __user *) arg;
308 
309         pr_debug("%s: group=%p cmd=%u\n", __func__, group, cmd);
310 
311         switch (cmd) {
312         case FIONREAD:
313                 mutex_lock(&group->notification_mutex);
314                 list_for_each_entry(holder, &group->notification_list, event_list) {
315                         event = holder->event;
316                         send_len += sizeof(struct inotify_event);
317                         if (event->name_len)
318                                 send_len += roundup(event->name_len + 1,
319                                                 sizeof(struct inotify_event));
320                 }
321                 mutex_unlock(&group->notification_mutex);
322                 ret = put_user(send_len, (int __user *) p);
323                 break;
324         }
325 
326         return ret;
327 }
328 
329 static const struct file_operations inotify_fops = {
330         .show_fdinfo    = inotify_show_fdinfo,
331         .poll           = inotify_poll,
332         .read           = inotify_read,
333         .fasync         = fsnotify_fasync,
334         .release        = inotify_release,
335         .unlocked_ioctl = inotify_ioctl,
336         .compat_ioctl   = inotify_ioctl,
337         .llseek         = noop_llseek,
338 };
339 
340 
341 /*
342  * find_inode - resolve a user-given path to a specific inode
343  */
344 static int inotify_find_inode(const char __user *dirname, struct path *path, unsigned flags)
345 {
346         int error;
347 
348         error = user_path_at(AT_FDCWD, dirname, flags, path);
349         if (error)
350                 return error;
351         /* you can only watch an inode if you have read permissions on it */
352         error = inode_permission(path->dentry->d_inode, MAY_READ);
353         if (error)
354                 path_put(path);
355         return error;
356 }
357 
358 static int inotify_add_to_idr(struct idr *idr, spinlock_t *idr_lock,
359                               struct inotify_inode_mark *i_mark)
360 {
361         int ret;
362 
363         idr_preload(GFP_KERNEL);
364         spin_lock(idr_lock);
365 
366         ret = idr_alloc_cyclic(idr, i_mark, 1, 0, GFP_NOWAIT);
367         if (ret >= 0) {
368                 /* we added the mark to the idr, take a reference */
369                 i_mark->wd = ret;
370                 fsnotify_get_mark(&i_mark->fsn_mark);
371         }
372 
373         spin_unlock(idr_lock);
374         idr_preload_end();
375         return ret < 0 ? ret : 0;
376 }
377 
378 static struct inotify_inode_mark *inotify_idr_find_locked(struct fsnotify_group *group,
379                                                                 int wd)
380 {
381         struct idr *idr = &group->inotify_data.idr;
382         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
383         struct inotify_inode_mark *i_mark;
384 
385         assert_spin_locked(idr_lock);
386 
387         i_mark = idr_find(idr, wd);
388         if (i_mark) {
389                 struct fsnotify_mark *fsn_mark = &i_mark->fsn_mark;
390 
391                 fsnotify_get_mark(fsn_mark);
392                 /* One ref for being in the idr, one ref we just took */
393                 BUG_ON(atomic_read(&fsn_mark->refcnt) < 2);
394         }
395 
396         return i_mark;
397 }
398 
399 static struct inotify_inode_mark *inotify_idr_find(struct fsnotify_group *group,
400                                                          int wd)
401 {
402         struct inotify_inode_mark *i_mark;
403         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
404 
405         spin_lock(idr_lock);
406         i_mark = inotify_idr_find_locked(group, wd);
407         spin_unlock(idr_lock);
408 
409         return i_mark;
410 }
411 
412 static void do_inotify_remove_from_idr(struct fsnotify_group *group,
413                                        struct inotify_inode_mark *i_mark)
414 {
415         struct idr *idr = &group->inotify_data.idr;
416         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
417         int wd = i_mark->wd;
418 
419         assert_spin_locked(idr_lock);
420 
421         idr_remove(idr, wd);
422 
423         /* removed from the idr, drop that ref */
424         fsnotify_put_mark(&i_mark->fsn_mark);
425 }
426 
427 /*
428  * Remove the mark from the idr (if present) and drop the reference
429  * on the mark because it was in the idr.
430  */
431 static void inotify_remove_from_idr(struct fsnotify_group *group,
432                                     struct inotify_inode_mark *i_mark)
433 {
434         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
435         struct inotify_inode_mark *found_i_mark = NULL;
436         int wd;
437 
438         spin_lock(idr_lock);
439         wd = i_mark->wd;
440 
441         /*
442          * does this i_mark think it is in the idr?  we shouldn't get called
443          * if it wasn't....
444          */
445         if (wd == -1) {
446                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
447                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
448                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
449                 goto out;
450         }
451 
452         /* Lets look in the idr to see if we find it */
453         found_i_mark = inotify_idr_find_locked(group, wd);
454         if (unlikely(!found_i_mark)) {
455                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
456                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
457                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
458                 goto out;
459         }
460 
461         /*
462          * We found an mark in the idr at the right wd, but it's
463          * not the mark we were told to remove.  eparis seriously
464          * fucked up somewhere.
465          */
466         if (unlikely(found_i_mark != i_mark)) {
467                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p "
468                         "mark->inode=%p found_i_mark=%p found_i_mark->wd=%d "
469                         "found_i_mark->group=%p found_i_mark->inode=%p\n",
470                         __func__, i_mark, i_mark->wd, i_mark->fsn_mark.group,
471                         i_mark->fsn_mark.i.inode, found_i_mark, found_i_mark->wd,
472                         found_i_mark->fsn_mark.group,
473                         found_i_mark->fsn_mark.i.inode);
474                 goto out;
475         }
476 
477         /*
478          * One ref for being in the idr
479          * one ref held by the caller trying to kill us
480          * one ref grabbed by inotify_idr_find
481          */
482         if (unlikely(atomic_read(&i_mark->fsn_mark.refcnt) < 3)) {
483                 printk(KERN_ERR "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
484                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
485                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
486                 /* we can't really recover with bad ref cnting.. */
487                 BUG();
488         }
489 
490         do_inotify_remove_from_idr(group, i_mark);
491 out:
492         /* match the ref taken by inotify_idr_find_locked() */
493         if (found_i_mark)
494                 fsnotify_put_mark(&found_i_mark->fsn_mark);
495         i_mark->wd = -1;
496         spin_unlock(idr_lock);
497 }
498 
499 /*
500  * Send IN_IGNORED for this wd, remove this wd from the idr.
501  */
502 void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,
503                                     struct fsnotify_group *group)
504 {
505         struct inotify_inode_mark *i_mark;
506         struct fsnotify_event *ignored_event, *notify_event;
507         struct inotify_event_private_data *event_priv;
508         struct fsnotify_event_private_data *fsn_event_priv;
509         int ret;
510 
511         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
512 
513         ignored_event = fsnotify_create_event(NULL, FS_IN_IGNORED, NULL,
514                                               FSNOTIFY_EVENT_NONE, NULL, 0,
515                                               GFP_NOFS);
516         if (!ignored_event)
517                 goto skip_send_ignore;
518 
519         event_priv = kmem_cache_alloc(event_priv_cachep, GFP_NOFS);
520         if (unlikely(!event_priv))
521                 goto skip_send_ignore;
522 
523         fsn_event_priv = &event_priv->fsnotify_event_priv_data;
524 
525         fsnotify_get_group(group);
526         fsn_event_priv->group = group;
527         event_priv->wd = i_mark->wd;
528 
529         notify_event = fsnotify_add_notify_event(group, ignored_event, fsn_event_priv, NULL);
530         if (notify_event) {
531                 if (IS_ERR(notify_event))
532                         ret = PTR_ERR(notify_event);
533                 else
534                         fsnotify_put_event(notify_event);
535                 inotify_free_event_priv(fsn_event_priv);
536         }
537 
538 skip_send_ignore:
539         /* matches the reference taken when the event was created */
540         if (ignored_event)
541                 fsnotify_put_event(ignored_event);
542 
543         /* remove this mark from the idr */
544         inotify_remove_from_idr(group, i_mark);
545 
546         atomic_dec(&group->inotify_data.user->inotify_watches);
547 }
548 
549 /* ding dong the mark is dead */
550 static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
551 {
552         struct inotify_inode_mark *i_mark;
553 
554         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
555 
556         kmem_cache_free(inotify_inode_mark_cachep, i_mark);
557 }
558 
559 static int inotify_update_existing_watch(struct fsnotify_group *group,
560                                          struct inode *inode,
561                                          u32 arg)
562 {
563         struct fsnotify_mark *fsn_mark;
564         struct inotify_inode_mark *i_mark;
565         __u32 old_mask, new_mask;
566         __u32 mask;
567         int add = (arg & IN_MASK_ADD);
568         int ret;
569 
570         mask = inotify_arg_to_mask(arg);
571 
572         fsn_mark = fsnotify_find_inode_mark(group, inode);
573         if (!fsn_mark)
574                 return -ENOENT;
575 
576         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
577 
578         spin_lock(&fsn_mark->lock);
579 
580         old_mask = fsn_mark->mask;
581         if (add)
582                 fsnotify_set_mark_mask_locked(fsn_mark, (fsn_mark->mask | mask));
583         else
584                 fsnotify_set_mark_mask_locked(fsn_mark, mask);
585         new_mask = fsn_mark->mask;
586 
587         spin_unlock(&fsn_mark->lock);
588 
589         if (old_mask != new_mask) {
590                 /* more bits in old than in new? */
591                 int dropped = (old_mask & ~new_mask);
592                 /* more bits in this fsn_mark than the inode's mask? */
593                 int do_inode = (new_mask & ~inode->i_fsnotify_mask);
594 
595                 /* update the inode with this new fsn_mark */
596                 if (dropped || do_inode)
597                         fsnotify_recalc_inode_mask(inode);
598 
599         }
600 
601         /* return the wd */
602         ret = i_mark->wd;
603 
604         /* match the get from fsnotify_find_mark() */
605         fsnotify_put_mark(fsn_mark);
606 
607         return ret;
608 }
609 
610 static int inotify_new_watch(struct fsnotify_group *group,
611                              struct inode *inode,
612                              u32 arg)
613 {
614         struct inotify_inode_mark *tmp_i_mark;
615         __u32 mask;
616         int ret;
617         struct idr *idr = &group->inotify_data.idr;
618         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
619 
620         mask = inotify_arg_to_mask(arg);
621 
622         tmp_i_mark = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
623         if (unlikely(!tmp_i_mark))
624                 return -ENOMEM;
625 
626         fsnotify_init_mark(&tmp_i_mark->fsn_mark, inotify_free_mark);
627         tmp_i_mark->fsn_mark.mask = mask;
628         tmp_i_mark->wd = -1;
629 
630         ret = -ENOSPC;
631         if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
632                 goto out_err;
633 
634         ret = inotify_add_to_idr(idr, idr_lock, tmp_i_mark);
635         if (ret)
636                 goto out_err;
637 
638         /* we are on the idr, now get on the inode */
639         ret = fsnotify_add_mark_locked(&tmp_i_mark->fsn_mark, group, inode,
640                                        NULL, 0);
641         if (ret) {
642                 /* we failed to get on the inode, get off the idr */
643                 inotify_remove_from_idr(group, tmp_i_mark);
644                 goto out_err;
645         }
646 
647         /* increment the number of watches the user has */
648         atomic_inc(&group->inotify_data.user->inotify_watches);
649 
650         /* return the watch descriptor for this new mark */
651         ret = tmp_i_mark->wd;
652 
653 out_err:
654         /* match the ref from fsnotify_init_mark() */
655         fsnotify_put_mark(&tmp_i_mark->fsn_mark);
656 
657         return ret;
658 }
659 
660 static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
661 {
662         int ret = 0;
663 
664         mutex_lock(&group->mark_mutex);
665         /* try to update and existing watch with the new arg */
666         ret = inotify_update_existing_watch(group, inode, arg);
667         /* no mark present, try to add a new one */
668         if (ret == -ENOENT)
669                 ret = inotify_new_watch(group, inode, arg);
670         mutex_unlock(&group->mark_mutex);
671 
672         return ret;
673 }
674 
675 static struct fsnotify_group *inotify_new_group(unsigned int max_events)
676 {
677         struct fsnotify_group *group;
678 
679         group = fsnotify_alloc_group(&inotify_fsnotify_ops);
680         if (IS_ERR(group))
681                 return group;
682 
683         group->max_events = max_events;
684 
685         spin_lock_init(&group->inotify_data.idr_lock);
686         idr_init(&group->inotify_data.idr);
687         group->inotify_data.user = get_current_user();
688 
689         if (atomic_inc_return(&group->inotify_data.user->inotify_devs) >
690             inotify_max_user_instances) {
691                 fsnotify_destroy_group(group);
692                 return ERR_PTR(-EMFILE);
693         }
694 
695         return group;
696 }
697 
698 
699 /* inotify syscalls */
700 SYSCALL_DEFINE1(inotify_init1, int, flags)
701 {
702         struct fsnotify_group *group;
703         int ret;
704 
705         /* Check the IN_* constants for consistency.  */
706         BUILD_BUG_ON(IN_CLOEXEC != O_CLOEXEC);
707         BUILD_BUG_ON(IN_NONBLOCK != O_NONBLOCK);
708 
709         if (flags & ~(IN_CLOEXEC | IN_NONBLOCK))
710                 return -EINVAL;
711 
712         /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
713         group = inotify_new_group(inotify_max_queued_events);
714         if (IS_ERR(group))
715                 return PTR_ERR(group);
716 
717         ret = anon_inode_getfd("inotify", &inotify_fops, group,
718                                   O_RDONLY | flags);
719         if (ret < 0)
720                 fsnotify_destroy_group(group);
721 
722         return ret;
723 }
724 
725 SYSCALL_DEFINE0(inotify_init)
726 {
727         return sys_inotify_init1(0);
728 }
729 
730 SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
731                 u32, mask)
732 {
733         struct fsnotify_group *group;
734         struct inode *inode;
735         struct path path;
736         struct fd f;
737         int ret;
738         unsigned flags = 0;
739 
740         /* don't allow invalid bits: we don't want flags set */
741         if (unlikely(!(mask & ALL_INOTIFY_BITS)))
742                 return -EINVAL;
743 
744         f = fdget(fd);
745         if (unlikely(!f.file))
746                 return -EBADF;
747 
748         /* verify that this is indeed an inotify instance */
749         if (unlikely(f.file->f_op != &inotify_fops)) {
750                 ret = -EINVAL;
751                 goto fput_and_out;
752         }
753 
754         if (!(mask & IN_DONT_FOLLOW))
755                 flags |= LOOKUP_FOLLOW;
756         if (mask & IN_ONLYDIR)
757                 flags |= LOOKUP_DIRECTORY;
758 
759         ret = inotify_find_inode(pathname, &path, flags);
760         if (ret)
761                 goto fput_and_out;
762 
763         /* inode held in place by reference to path; group by fget on fd */
764         inode = path.dentry->d_inode;
765         group = f.file->private_data;
766 
767         /* create/update an inode mark */
768         ret = inotify_update_watch(group, inode, mask);
769         path_put(&path);
770 fput_and_out:
771         fdput(f);
772         return ret;
773 }
774 
775 SYSCALL_DEFINE2(inotify_rm_watch, int, fd, __s32, wd)
776 {
777         struct fsnotify_group *group;
778         struct inotify_inode_mark *i_mark;
779         struct fd f;
780         int ret = 0;
781 
782         f = fdget(fd);
783         if (unlikely(!f.file))
784                 return -EBADF;
785 
786         /* verify that this is indeed an inotify instance */
787         ret = -EINVAL;
788         if (unlikely(f.file->f_op != &inotify_fops))
789                 goto out;
790 
791         group = f.file->private_data;
792 
793         ret = -EINVAL;
794         i_mark = inotify_idr_find(group, wd);
795         if (unlikely(!i_mark))
796                 goto out;
797 
798         ret = 0;
799 
800         fsnotify_destroy_mark(&i_mark->fsn_mark, group);
801 
802         /* match ref taken by inotify_idr_find */
803         fsnotify_put_mark(&i_mark->fsn_mark);
804 
805 out:
806         fdput(f);
807         return ret;
808 }
809 
810 /*
811  * inotify_user_setup - Our initialization function.  Note that we cannot return
812  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
813  * must result in panic().
814  */
815 static int __init inotify_user_setup(void)
816 {
817         BUILD_BUG_ON(IN_ACCESS != FS_ACCESS);
818         BUILD_BUG_ON(IN_MODIFY != FS_MODIFY);
819         BUILD_BUG_ON(IN_ATTRIB != FS_ATTRIB);
820         BUILD_BUG_ON(IN_CLOSE_WRITE != FS_CLOSE_WRITE);
821         BUILD_BUG_ON(IN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
822         BUILD_BUG_ON(IN_OPEN != FS_OPEN);
823         BUILD_BUG_ON(IN_MOVED_FROM != FS_MOVED_FROM);
824         BUILD_BUG_ON(IN_MOVED_TO != FS_MOVED_TO);
825         BUILD_BUG_ON(IN_CREATE != FS_CREATE);
826         BUILD_BUG_ON(IN_DELETE != FS_DELETE);
827         BUILD_BUG_ON(IN_DELETE_SELF != FS_DELETE_SELF);
828         BUILD_BUG_ON(IN_MOVE_SELF != FS_MOVE_SELF);
829         BUILD_BUG_ON(IN_UNMOUNT != FS_UNMOUNT);
830         BUILD_BUG_ON(IN_Q_OVERFLOW != FS_Q_OVERFLOW);
831         BUILD_BUG_ON(IN_IGNORED != FS_IN_IGNORED);
832         BUILD_BUG_ON(IN_EXCL_UNLINK != FS_EXCL_UNLINK);
833         BUILD_BUG_ON(IN_ISDIR != FS_ISDIR);
834         BUILD_BUG_ON(IN_ONESHOT != FS_IN_ONESHOT);
835 
836         BUG_ON(hweight32(ALL_INOTIFY_BITS) != 21);
837 
838         inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark, SLAB_PANIC);
839         event_priv_cachep = KMEM_CACHE(inotify_event_private_data, SLAB_PANIC);
840 
841         inotify_max_queued_events = 16384;
842         inotify_max_user_instances = 128;
843         inotify_max_user_watches = 8192;
844 
845         return 0;
846 }
847 module_init(inotify_user_setup);
848 

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