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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         if (file->f_flags & FASYNC)
291                 fsnotify_fasync(-1, file, 0);
292 
293         /* free this group, matching get was inotify_init->fsnotify_obtain_group */
294         fsnotify_destroy_group(group);
295 
296         return 0;
297 }
298 
299 static long inotify_ioctl(struct file *file, unsigned int cmd,
300                           unsigned long arg)
301 {
302         struct fsnotify_group *group;
303         struct fsnotify_event_holder *holder;
304         struct fsnotify_event *event;
305         void __user *p;
306         int ret = -ENOTTY;
307         size_t send_len = 0;
308 
309         group = file->private_data;
310         p = (void __user *) arg;
311 
312         pr_debug("%s: group=%p cmd=%u\n", __func__, group, cmd);
313 
314         switch (cmd) {
315         case FIONREAD:
316                 mutex_lock(&group->notification_mutex);
317                 list_for_each_entry(holder, &group->notification_list, event_list) {
318                         event = holder->event;
319                         send_len += sizeof(struct inotify_event);
320                         if (event->name_len)
321                                 send_len += roundup(event->name_len + 1,
322                                                 sizeof(struct inotify_event));
323                 }
324                 mutex_unlock(&group->notification_mutex);
325                 ret = put_user(send_len, (int __user *) p);
326                 break;
327         }
328 
329         return ret;
330 }
331 
332 static const struct file_operations inotify_fops = {
333         .show_fdinfo    = inotify_show_fdinfo,
334         .poll           = inotify_poll,
335         .read           = inotify_read,
336         .fasync         = fsnotify_fasync,
337         .release        = inotify_release,
338         .unlocked_ioctl = inotify_ioctl,
339         .compat_ioctl   = inotify_ioctl,
340         .llseek         = noop_llseek,
341 };
342 
343 
344 /*
345  * find_inode - resolve a user-given path to a specific inode
346  */
347 static int inotify_find_inode(const char __user *dirname, struct path *path, unsigned flags)
348 {
349         int error;
350 
351         error = user_path_at(AT_FDCWD, dirname, flags, path);
352         if (error)
353                 return error;
354         /* you can only watch an inode if you have read permissions on it */
355         error = inode_permission(path->dentry->d_inode, MAY_READ);
356         if (error)
357                 path_put(path);
358         return error;
359 }
360 
361 static int inotify_add_to_idr(struct idr *idr, spinlock_t *idr_lock,
362                               int *last_wd,
363                               struct inotify_inode_mark *i_mark)
364 {
365         int ret;
366 
367         idr_preload(GFP_KERNEL);
368         spin_lock(idr_lock);
369 
370         ret = idr_alloc(idr, i_mark, *last_wd + 1, 0, GFP_NOWAIT);
371         if (ret >= 0) {
372                 /* we added the mark to the idr, take a reference */
373                 i_mark->wd = ret;
374                 *last_wd = i_mark->wd;
375                 fsnotify_get_mark(&i_mark->fsn_mark);
376         }
377 
378         spin_unlock(idr_lock);
379         idr_preload_end();
380         return ret < 0 ? ret : 0;
381 }
382 
383 static struct inotify_inode_mark *inotify_idr_find_locked(struct fsnotify_group *group,
384                                                                 int wd)
385 {
386         struct idr *idr = &group->inotify_data.idr;
387         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
388         struct inotify_inode_mark *i_mark;
389 
390         assert_spin_locked(idr_lock);
391 
392         i_mark = idr_find(idr, wd);
393         if (i_mark) {
394                 struct fsnotify_mark *fsn_mark = &i_mark->fsn_mark;
395 
396                 fsnotify_get_mark(fsn_mark);
397                 /* One ref for being in the idr, one ref we just took */
398                 BUG_ON(atomic_read(&fsn_mark->refcnt) < 2);
399         }
400 
401         return i_mark;
402 }
403 
404 static struct inotify_inode_mark *inotify_idr_find(struct fsnotify_group *group,
405                                                          int wd)
406 {
407         struct inotify_inode_mark *i_mark;
408         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
409 
410         spin_lock(idr_lock);
411         i_mark = inotify_idr_find_locked(group, wd);
412         spin_unlock(idr_lock);
413 
414         return i_mark;
415 }
416 
417 static void do_inotify_remove_from_idr(struct fsnotify_group *group,
418                                        struct inotify_inode_mark *i_mark)
419 {
420         struct idr *idr = &group->inotify_data.idr;
421         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
422         int wd = i_mark->wd;
423 
424         assert_spin_locked(idr_lock);
425 
426         idr_remove(idr, wd);
427 
428         /* removed from the idr, drop that ref */
429         fsnotify_put_mark(&i_mark->fsn_mark);
430 }
431 
432 /*
433  * Remove the mark from the idr (if present) and drop the reference
434  * on the mark because it was in the idr.
435  */
436 static void inotify_remove_from_idr(struct fsnotify_group *group,
437                                     struct inotify_inode_mark *i_mark)
438 {
439         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
440         struct inotify_inode_mark *found_i_mark = NULL;
441         int wd;
442 
443         spin_lock(idr_lock);
444         wd = i_mark->wd;
445 
446         /*
447          * does this i_mark think it is in the idr?  we shouldn't get called
448          * if it wasn't....
449          */
450         if (wd == -1) {
451                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
452                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
453                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
454                 goto out;
455         }
456 
457         /* Lets look in the idr to see if we find it */
458         found_i_mark = inotify_idr_find_locked(group, wd);
459         if (unlikely(!found_i_mark)) {
460                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
461                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
462                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
463                 goto out;
464         }
465 
466         /*
467          * We found an mark in the idr at the right wd, but it's
468          * not the mark we were told to remove.  eparis seriously
469          * fucked up somewhere.
470          */
471         if (unlikely(found_i_mark != i_mark)) {
472                 WARN_ONCE(1, "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p "
473                         "mark->inode=%p found_i_mark=%p found_i_mark->wd=%d "
474                         "found_i_mark->group=%p found_i_mark->inode=%p\n",
475                         __func__, i_mark, i_mark->wd, i_mark->fsn_mark.group,
476                         i_mark->fsn_mark.i.inode, found_i_mark, found_i_mark->wd,
477                         found_i_mark->fsn_mark.group,
478                         found_i_mark->fsn_mark.i.inode);
479                 goto out;
480         }
481 
482         /*
483          * One ref for being in the idr
484          * one ref held by the caller trying to kill us
485          * one ref grabbed by inotify_idr_find
486          */
487         if (unlikely(atomic_read(&i_mark->fsn_mark.refcnt) < 3)) {
488                 printk(KERN_ERR "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p"
489                         " i_mark->inode=%p\n", __func__, i_mark, i_mark->wd,
490                         i_mark->fsn_mark.group, i_mark->fsn_mark.i.inode);
491                 /* we can't really recover with bad ref cnting.. */
492                 BUG();
493         }
494 
495         do_inotify_remove_from_idr(group, i_mark);
496 out:
497         /* match the ref taken by inotify_idr_find_locked() */
498         if (found_i_mark)
499                 fsnotify_put_mark(&found_i_mark->fsn_mark);
500         i_mark->wd = -1;
501         spin_unlock(idr_lock);
502 }
503 
504 /*
505  * Send IN_IGNORED for this wd, remove this wd from the idr.
506  */
507 void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,
508                                     struct fsnotify_group *group)
509 {
510         struct inotify_inode_mark *i_mark;
511         struct fsnotify_event *ignored_event, *notify_event;
512         struct inotify_event_private_data *event_priv;
513         struct fsnotify_event_private_data *fsn_event_priv;
514         int ret;
515 
516         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
517 
518         ignored_event = fsnotify_create_event(NULL, FS_IN_IGNORED, NULL,
519                                               FSNOTIFY_EVENT_NONE, NULL, 0,
520                                               GFP_NOFS);
521         if (!ignored_event)
522                 goto skip_send_ignore;
523 
524         event_priv = kmem_cache_alloc(event_priv_cachep, GFP_NOFS);
525         if (unlikely(!event_priv))
526                 goto skip_send_ignore;
527 
528         fsn_event_priv = &event_priv->fsnotify_event_priv_data;
529 
530         fsnotify_get_group(group);
531         fsn_event_priv->group = group;
532         event_priv->wd = i_mark->wd;
533 
534         notify_event = fsnotify_add_notify_event(group, ignored_event, fsn_event_priv, NULL);
535         if (notify_event) {
536                 if (IS_ERR(notify_event))
537                         ret = PTR_ERR(notify_event);
538                 else
539                         fsnotify_put_event(notify_event);
540                 inotify_free_event_priv(fsn_event_priv);
541         }
542 
543 skip_send_ignore:
544         /* matches the reference taken when the event was created */
545         if (ignored_event)
546                 fsnotify_put_event(ignored_event);
547 
548         /* remove this mark from the idr */
549         inotify_remove_from_idr(group, i_mark);
550 
551         atomic_dec(&group->inotify_data.user->inotify_watches);
552 }
553 
554 /* ding dong the mark is dead */
555 static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
556 {
557         struct inotify_inode_mark *i_mark;
558 
559         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
560 
561         kmem_cache_free(inotify_inode_mark_cachep, i_mark);
562 }
563 
564 static int inotify_update_existing_watch(struct fsnotify_group *group,
565                                          struct inode *inode,
566                                          u32 arg)
567 {
568         struct fsnotify_mark *fsn_mark;
569         struct inotify_inode_mark *i_mark;
570         __u32 old_mask, new_mask;
571         __u32 mask;
572         int add = (arg & IN_MASK_ADD);
573         int ret;
574 
575         mask = inotify_arg_to_mask(arg);
576 
577         fsn_mark = fsnotify_find_inode_mark(group, inode);
578         if (!fsn_mark)
579                 return -ENOENT;
580 
581         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
582 
583         spin_lock(&fsn_mark->lock);
584 
585         old_mask = fsn_mark->mask;
586         if (add)
587                 fsnotify_set_mark_mask_locked(fsn_mark, (fsn_mark->mask | mask));
588         else
589                 fsnotify_set_mark_mask_locked(fsn_mark, mask);
590         new_mask = fsn_mark->mask;
591 
592         spin_unlock(&fsn_mark->lock);
593 
594         if (old_mask != new_mask) {
595                 /* more bits in old than in new? */
596                 int dropped = (old_mask & ~new_mask);
597                 /* more bits in this fsn_mark than the inode's mask? */
598                 int do_inode = (new_mask & ~inode->i_fsnotify_mask);
599 
600                 /* update the inode with this new fsn_mark */
601                 if (dropped || do_inode)
602                         fsnotify_recalc_inode_mask(inode);
603 
604         }
605 
606         /* return the wd */
607         ret = i_mark->wd;
608 
609         /* match the get from fsnotify_find_mark() */
610         fsnotify_put_mark(fsn_mark);
611 
612         return ret;
613 }
614 
615 static int inotify_new_watch(struct fsnotify_group *group,
616                              struct inode *inode,
617                              u32 arg)
618 {
619         struct inotify_inode_mark *tmp_i_mark;
620         __u32 mask;
621         int ret;
622         struct idr *idr = &group->inotify_data.idr;
623         spinlock_t *idr_lock = &group->inotify_data.idr_lock;
624 
625         mask = inotify_arg_to_mask(arg);
626 
627         tmp_i_mark = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
628         if (unlikely(!tmp_i_mark))
629                 return -ENOMEM;
630 
631         fsnotify_init_mark(&tmp_i_mark->fsn_mark, inotify_free_mark);
632         tmp_i_mark->fsn_mark.mask = mask;
633         tmp_i_mark->wd = -1;
634 
635         ret = -ENOSPC;
636         if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
637                 goto out_err;
638 
639         ret = inotify_add_to_idr(idr, idr_lock, &group->inotify_data.last_wd,
640                                  tmp_i_mark);
641         if (ret)
642                 goto out_err;
643 
644         /* we are on the idr, now get on the inode */
645         ret = fsnotify_add_mark(&tmp_i_mark->fsn_mark, group, inode, NULL, 0);
646         if (ret) {
647                 /* we failed to get on the inode, get off the idr */
648                 inotify_remove_from_idr(group, tmp_i_mark);
649                 goto out_err;
650         }
651 
652         /* increment the number of watches the user has */
653         atomic_inc(&group->inotify_data.user->inotify_watches);
654 
655         /* return the watch descriptor for this new mark */
656         ret = tmp_i_mark->wd;
657 
658 out_err:
659         /* match the ref from fsnotify_init_mark() */
660         fsnotify_put_mark(&tmp_i_mark->fsn_mark);
661 
662         return ret;
663 }
664 
665 static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
666 {
667         int ret = 0;
668 
669 retry:
670         /* try to update and existing watch with the new arg */
671         ret = inotify_update_existing_watch(group, inode, arg);
672         /* no mark present, try to add a new one */
673         if (ret == -ENOENT)
674                 ret = inotify_new_watch(group, inode, arg);
675         /*
676          * inotify_new_watch could race with another thread which did an
677          * inotify_new_watch between the update_existing and the add watch
678          * here, go back and try to update an existing mark again.
679          */
680         if (ret == -EEXIST)
681                 goto retry;
682 
683         return ret;
684 }
685 
686 static struct fsnotify_group *inotify_new_group(unsigned int max_events)
687 {
688         struct fsnotify_group *group;
689 
690         group = fsnotify_alloc_group(&inotify_fsnotify_ops);
691         if (IS_ERR(group))
692                 return group;
693 
694         group->max_events = max_events;
695 
696         spin_lock_init(&group->inotify_data.idr_lock);
697         idr_init(&group->inotify_data.idr);
698         group->inotify_data.last_wd = 0;
699         group->inotify_data.user = get_current_user();
700 
701         if (atomic_inc_return(&group->inotify_data.user->inotify_devs) >
702             inotify_max_user_instances) {
703                 fsnotify_destroy_group(group);
704                 return ERR_PTR(-EMFILE);
705         }
706 
707         return group;
708 }
709 
710 
711 /* inotify syscalls */
712 SYSCALL_DEFINE1(inotify_init1, int, flags)
713 {
714         struct fsnotify_group *group;
715         int ret;
716 
717         /* Check the IN_* constants for consistency.  */
718         BUILD_BUG_ON(IN_CLOEXEC != O_CLOEXEC);
719         BUILD_BUG_ON(IN_NONBLOCK != O_NONBLOCK);
720 
721         if (flags & ~(IN_CLOEXEC | IN_NONBLOCK))
722                 return -EINVAL;
723 
724         /* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
725         group = inotify_new_group(inotify_max_queued_events);
726         if (IS_ERR(group))
727                 return PTR_ERR(group);
728 
729         ret = anon_inode_getfd("inotify", &inotify_fops, group,
730                                   O_RDONLY | flags);
731         if (ret < 0)
732                 fsnotify_destroy_group(group);
733 
734         return ret;
735 }
736 
737 SYSCALL_DEFINE0(inotify_init)
738 {
739         return sys_inotify_init1(0);
740 }
741 
742 SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
743                 u32, mask)
744 {
745         struct fsnotify_group *group;
746         struct inode *inode;
747         struct path path;
748         struct fd f;
749         int ret;
750         unsigned flags = 0;
751 
752         /* don't allow invalid bits: we don't want flags set */
753         if (unlikely(!(mask & ALL_INOTIFY_BITS)))
754                 return -EINVAL;
755 
756         f = fdget(fd);
757         if (unlikely(!f.file))
758                 return -EBADF;
759 
760         /* verify that this is indeed an inotify instance */
761         if (unlikely(f.file->f_op != &inotify_fops)) {
762                 ret = -EINVAL;
763                 goto fput_and_out;
764         }
765 
766         if (!(mask & IN_DONT_FOLLOW))
767                 flags |= LOOKUP_FOLLOW;
768         if (mask & IN_ONLYDIR)
769                 flags |= LOOKUP_DIRECTORY;
770 
771         ret = inotify_find_inode(pathname, &path, flags);
772         if (ret)
773                 goto fput_and_out;
774 
775         /* inode held in place by reference to path; group by fget on fd */
776         inode = path.dentry->d_inode;
777         group = f.file->private_data;
778 
779         /* create/update an inode mark */
780         ret = inotify_update_watch(group, inode, mask);
781         path_put(&path);
782 fput_and_out:
783         fdput(f);
784         return ret;
785 }
786 
787 SYSCALL_DEFINE2(inotify_rm_watch, int, fd, __s32, wd)
788 {
789         struct fsnotify_group *group;
790         struct inotify_inode_mark *i_mark;
791         struct fd f;
792         int ret = 0;
793 
794         f = fdget(fd);
795         if (unlikely(!f.file))
796                 return -EBADF;
797 
798         /* verify that this is indeed an inotify instance */
799         ret = -EINVAL;
800         if (unlikely(f.file->f_op != &inotify_fops))
801                 goto out;
802 
803         group = f.file->private_data;
804 
805         ret = -EINVAL;
806         i_mark = inotify_idr_find(group, wd);
807         if (unlikely(!i_mark))
808                 goto out;
809 
810         ret = 0;
811 
812         fsnotify_destroy_mark(&i_mark->fsn_mark, group);
813 
814         /* match ref taken by inotify_idr_find */
815         fsnotify_put_mark(&i_mark->fsn_mark);
816 
817 out:
818         fdput(f);
819         return ret;
820 }
821 
822 /*
823  * inotify_user_setup - Our initialization function.  Note that we cannot return
824  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
825  * must result in panic().
826  */
827 static int __init inotify_user_setup(void)
828 {
829         BUILD_BUG_ON(IN_ACCESS != FS_ACCESS);
830         BUILD_BUG_ON(IN_MODIFY != FS_MODIFY);
831         BUILD_BUG_ON(IN_ATTRIB != FS_ATTRIB);
832         BUILD_BUG_ON(IN_CLOSE_WRITE != FS_CLOSE_WRITE);
833         BUILD_BUG_ON(IN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
834         BUILD_BUG_ON(IN_OPEN != FS_OPEN);
835         BUILD_BUG_ON(IN_MOVED_FROM != FS_MOVED_FROM);
836         BUILD_BUG_ON(IN_MOVED_TO != FS_MOVED_TO);
837         BUILD_BUG_ON(IN_CREATE != FS_CREATE);
838         BUILD_BUG_ON(IN_DELETE != FS_DELETE);
839         BUILD_BUG_ON(IN_DELETE_SELF != FS_DELETE_SELF);
840         BUILD_BUG_ON(IN_MOVE_SELF != FS_MOVE_SELF);
841         BUILD_BUG_ON(IN_UNMOUNT != FS_UNMOUNT);
842         BUILD_BUG_ON(IN_Q_OVERFLOW != FS_Q_OVERFLOW);
843         BUILD_BUG_ON(IN_IGNORED != FS_IN_IGNORED);
844         BUILD_BUG_ON(IN_EXCL_UNLINK != FS_EXCL_UNLINK);
845         BUILD_BUG_ON(IN_ISDIR != FS_ISDIR);
846         BUILD_BUG_ON(IN_ONESHOT != FS_IN_ONESHOT);
847 
848         BUG_ON(hweight32(ALL_INOTIFY_BITS) != 21);
849 
850         inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark, SLAB_PANIC);
851         event_priv_cachep = KMEM_CACHE(inotify_event_private_data, SLAB_PANIC);
852 
853         inotify_max_queued_events = 16384;
854         inotify_max_user_instances = 128;
855         inotify_max_user_watches = 8192;
856 
857         return 0;
858 }
859 module_init(inotify_user_setup);
860 

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