1 #include <linux/fcntl.h>
2 #include <linux/file.h>
4 #include <linux/anon_inodes.h>
5 #include <linux/fsnotify_backend.h>
6 #include <linux/init.h>
7 #include <linux/mount.h>
8 #include <linux/namei.h>
9 #include <linux/poll.h>
10 #include <linux/security.h>
11 #include <linux/syscalls.h>
12 #include <linux/types.h>
13 #include <linux/uaccess.h>
15 #include <asm/ioctls.h>
19 static struct kmem_cache *fanotify_mark_cache __read_mostly;
22 * Get an fsnotify notification event if one exists and is small
23 * enough to fit in "count". Return an error pointer if the count
24 * is not large enough.
26 * Called with the group->notification_mutex held.
28 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
31 BUG_ON(!mutex_is_locked(&group->notification_mutex));
33 pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
35 if (fsnotify_notify_queue_is_empty(group))
38 if (FAN_EVENT_METADATA_LEN > count)
39 return ERR_PTR(-EINVAL);
41 /* held the notification_mutex the whole time, so this is the
42 * same event we peeked above */
43 return fsnotify_remove_notify_event(group);
46 static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
49 struct dentry *dentry;
51 struct file *new_file;
53 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
55 client_fd = get_unused_fd();
59 if (event->data_type != FSNOTIFY_EVENT_PATH) {
61 put_unused_fd(client_fd);
66 * we need a new file handle for the userspace program so it can read even if it was
67 * originally opened O_WRONLY.
69 dentry = dget(event->path.dentry);
70 mnt = mntget(event->path.mnt);
71 /* it's possible this event was an overflow event. in that case dentry and mnt
72 * are NULL; That's fine, just don't call dentry open */
74 new_file = dentry_open(dentry, mnt,
75 O_RDONLY | O_LARGEFILE | FMODE_NONOTIFY,
78 new_file = ERR_PTR(-EOVERFLOW);
79 if (IS_ERR(new_file)) {
81 * we still send an event even if we can't open the file. this
82 * can happen when say tasks are gone and we try to open their
83 * /proc files or we try to open a WRONLY file like in sysfs
84 * we just send the errno to userspace since there isn't much
87 put_unused_fd(client_fd);
88 client_fd = PTR_ERR(new_file);
90 fd_install(client_fd, new_file);
96 static ssize_t fill_event_metadata(struct fsnotify_group *group,
97 struct fanotify_event_metadata *metadata,
98 struct fsnotify_event *event)
100 pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
101 group, metadata, event);
103 metadata->event_len = FAN_EVENT_METADATA_LEN;
104 metadata->vers = FANOTIFY_METADATA_VERSION;
105 metadata->mask = fanotify_outgoing_mask(event->mask);
106 metadata->pid = pid_vnr(event->tgid);
107 metadata->fd = create_fd(group, event);
112 static ssize_t copy_event_to_user(struct fsnotify_group *group,
113 struct fsnotify_event *event,
116 struct fanotify_event_metadata fanotify_event_metadata;
119 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
121 ret = fill_event_metadata(group, &fanotify_event_metadata, event);
125 if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
128 return FAN_EVENT_METADATA_LEN;
131 /* intofiy userspace file descriptor functions */
132 static unsigned int fanotify_poll(struct file *file, poll_table *wait)
134 struct fsnotify_group *group = file->private_data;
137 poll_wait(file, &group->notification_waitq, wait);
138 mutex_lock(&group->notification_mutex);
139 if (!fsnotify_notify_queue_is_empty(group))
140 ret = POLLIN | POLLRDNORM;
141 mutex_unlock(&group->notification_mutex);
146 static ssize_t fanotify_read(struct file *file, char __user *buf,
147 size_t count, loff_t *pos)
149 struct fsnotify_group *group;
150 struct fsnotify_event *kevent;
156 group = file->private_data;
158 pr_debug("%s: group=%p\n", __func__, group);
161 prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
163 mutex_lock(&group->notification_mutex);
164 kevent = get_one_event(group, count);
165 mutex_unlock(&group->notification_mutex);
168 ret = PTR_ERR(kevent);
171 ret = copy_event_to_user(group, kevent, buf);
172 fsnotify_put_event(kevent);
181 if (file->f_flags & O_NONBLOCK)
184 if (signal_pending(current))
193 finish_wait(&group->notification_waitq, &wait);
194 if (start != buf && ret != -EFAULT)
199 static int fanotify_release(struct inode *ignored, struct file *file)
201 struct fsnotify_group *group = file->private_data;
203 pr_debug("%s: file=%p group=%p\n", __func__, file, group);
205 /* matches the fanotify_init->fsnotify_alloc_group */
206 fsnotify_put_group(group);
211 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
213 struct fsnotify_group *group;
214 struct fsnotify_event_holder *holder;
219 group = file->private_data;
221 p = (void __user *) arg;
225 mutex_lock(&group->notification_mutex);
226 list_for_each_entry(holder, &group->notification_list, event_list)
227 send_len += FAN_EVENT_METADATA_LEN;
228 mutex_unlock(&group->notification_mutex);
229 ret = put_user(send_len, (int __user *) p);
236 static const struct file_operations fanotify_fops = {
237 .poll = fanotify_poll,
238 .read = fanotify_read,
240 .release = fanotify_release,
241 .unlocked_ioctl = fanotify_ioctl,
242 .compat_ioctl = fanotify_ioctl,
245 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
247 kmem_cache_free(fanotify_mark_cache, fsn_mark);
250 static int fanotify_find_path(int dfd, const char __user *filename,
251 struct path *path, unsigned int flags)
255 pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
256 dfd, filename, flags);
258 if (filename == NULL) {
263 file = fget_light(dfd, &fput_needed);
268 if ((flags & FAN_MARK_ONLYDIR) &&
269 !(S_ISDIR(file->f_path.dentry->d_inode->i_mode))) {
270 fput_light(file, fput_needed);
274 *path = file->f_path;
276 fput_light(file, fput_needed);
278 unsigned int lookup_flags = 0;
280 if (!(flags & FAN_MARK_DONT_FOLLOW))
281 lookup_flags |= LOOKUP_FOLLOW;
282 if (flags & FAN_MARK_ONLYDIR)
283 lookup_flags |= LOOKUP_DIRECTORY;
285 ret = user_path_at(dfd, filename, lookup_flags, path);
290 /* you can only watch an inode if you have read permissions on it */
291 ret = inode_permission(path->dentry->d_inode, MAY_READ);
298 static int fanotify_remove_mark(struct fsnotify_group *group,
302 struct fsnotify_mark *fsn_mark;
305 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__,
308 fsn_mark = fsnotify_find_inode_mark(group, inode);
312 spin_lock(&fsn_mark->lock);
313 fsn_mark->mask &= ~mask;
314 new_mask = fsn_mark->mask;
315 spin_unlock(&fsn_mark->lock);
318 fsnotify_destroy_mark(fsn_mark);
320 fsnotify_recalc_inode_mask(inode);
322 fsnotify_recalc_group_mask(group);
324 /* matches the fsnotify_find_inode_mark() */
325 fsnotify_put_mark(fsn_mark);
330 static int fanotify_add_mark(struct fsnotify_group *group,
334 struct fsnotify_mark *fsn_mark;
335 __u32 old_mask, new_mask;
338 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__,
341 fsn_mark = fsnotify_find_inode_mark(group, inode);
343 struct fsnotify_mark *new_fsn_mark;
346 new_fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
350 fsnotify_init_mark(new_fsn_mark, fanotify_free_mark);
351 ret = fsnotify_add_mark(new_fsn_mark, group, inode, NULL, 0);
353 fanotify_free_mark(new_fsn_mark);
357 fsn_mark = new_fsn_mark;
362 spin_lock(&fsn_mark->lock);
363 old_mask = fsn_mark->mask;
364 fsn_mark->mask |= mask;
365 new_mask = fsn_mark->mask;
366 spin_unlock(&fsn_mark->lock);
368 /* we made changes to a mask, update the group mask and the inode mask
369 * so things happen quickly. */
370 if (old_mask != new_mask) {
371 /* more bits in old than in new? */
372 int dropped = (old_mask & ~new_mask);
373 /* more bits in this mark than the inode's mask? */
374 int do_inode = (new_mask & ~inode->i_fsnotify_mask);
375 /* more bits in this mark than the group? */
376 int do_group = (new_mask & ~group->mask);
378 /* update the inode with this new mark */
379 if (dropped || do_inode)
380 fsnotify_recalc_inode_mask(inode);
382 /* update the group mask with the new mask */
383 if (dropped || do_group)
384 fsnotify_recalc_group_mask(group);
387 /* match the init or the find.... */
388 fsnotify_put_mark(fsn_mark);
393 static int fanotify_update_mark(struct fsnotify_group *group,
394 struct inode *inode, int flags,
397 pr_debug("%s: group=%p inode=%p flags=%x mask=%x\n", __func__,
398 group, inode, flags, mask);
400 if (flags & FAN_MARK_ADD)
401 fanotify_add_mark(group, inode, mask);
402 else if (flags & FAN_MARK_REMOVE)
403 fanotify_remove_mark(group, inode, mask);
410 static bool fanotify_mark_validate_input(int flags,
413 pr_debug("%s: flags=%x mask=%x\n", __func__, flags, mask);
415 /* are flags valid of this operation? */
416 if (!fanotify_mark_flags_valid(flags))
418 /* is the mask valid? */
419 if (!fanotify_mask_valid(mask))
424 /* fanotify syscalls */
425 SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
426 unsigned int, priority)
428 struct fsnotify_group *group;
431 pr_debug("%s: flags=%d event_f_flags=%d priority=%d\n",
432 __func__, flags, event_f_flags, priority);
439 if (!capable(CAP_SYS_ADMIN))
442 if (flags & ~FAN_ALL_INIT_FLAGS)
445 f_flags = (O_RDONLY | FMODE_NONOTIFY);
446 if (flags & FAN_CLOEXEC)
447 f_flags |= O_CLOEXEC;
448 if (flags & FAN_NONBLOCK)
449 f_flags |= O_NONBLOCK;
451 /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
452 group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
454 return PTR_ERR(group);
456 fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
463 fsnotify_put_group(group);
467 SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int flags,
469 const char __user * pathname)
472 struct fsnotify_group *group;
475 int ret, fput_needed;
477 pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
478 __func__, fanotify_fd, flags, dfd, pathname, mask);
480 /* we only use the lower 32 bits as of right now. */
481 if (mask & ((__u64)0xffffffff << 32))
484 if (!fanotify_mark_validate_input(flags, mask))
487 filp = fget_light(fanotify_fd, &fput_needed);
491 /* verify that this is indeed an fanotify instance */
493 if (unlikely(filp->f_op != &fanotify_fops))
496 ret = fanotify_find_path(dfd, pathname, &path, flags);
500 /* inode held in place by reference to path; group by fget on fd */
501 inode = path.dentry->d_inode;
502 group = filp->private_data;
504 /* create/update an inode mark */
505 ret = fanotify_update_mark(group, inode, flags, mask);
509 fput_light(filp, fput_needed);
513 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
514 asmlinkage long SyS_fanotify_mark(long fanotify_fd, long flags, __u64 mask,
515 long dfd, long pathname)
517 return SYSC_fanotify_mark((int) fanotify_fd, (unsigned int) flags,
519 (const char __user *) pathname);
521 SYSCALL_ALIAS(sys_fanotify_mark, SyS_fanotify_mark);
525 * fanotify_user_setup - Our initialization function. Note that we cannnot return
526 * error because we have compiled-in VFS hooks. So an (unlikely) failure here
527 * must result in panic().
529 static int __init fanotify_user_setup(void)
531 fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
535 device_initcall(fanotify_user_setup);