236 lines
6.3 KiB
C
236 lines
6.3 KiB
C
#include <linux/fanotify.h>
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#include <linux/fdtable.h>
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#include <linux/fsnotify_backend.h>
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#include <linux/init.h>
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#include <linux/jiffies.h>
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#include <linux/kernel.h> /* UINT_MAX */
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#include <linux/mount.h>
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#include <linux/sched.h>
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#include <linux/types.h>
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#include <linux/wait.h>
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static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
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{
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pr_debug("%s: old=%p new=%p\n", __func__, old, new);
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if (old->to_tell == new->to_tell &&
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old->data_type == new->data_type &&
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old->tgid == new->tgid) {
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switch (old->data_type) {
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case (FSNOTIFY_EVENT_PATH):
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#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
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/* dont merge two permission events */
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if ((old->mask & FAN_ALL_PERM_EVENTS) &&
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(new->mask & FAN_ALL_PERM_EVENTS))
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return false;
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#endif
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if ((old->path.mnt == new->path.mnt) &&
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(old->path.dentry == new->path.dentry))
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return true;
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break;
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case (FSNOTIFY_EVENT_NONE):
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return true;
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default:
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BUG();
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};
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}
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return false;
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}
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/* and the list better be locked by something too! */
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static struct fsnotify_event *fanotify_merge(struct list_head *list,
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struct fsnotify_event *event)
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{
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struct fsnotify_event_holder *test_holder;
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struct fsnotify_event *test_event = NULL;
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struct fsnotify_event *new_event;
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pr_debug("%s: list=%p event=%p\n", __func__, list, event);
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list_for_each_entry_reverse(test_holder, list, event_list) {
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if (should_merge(test_holder->event, event)) {
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test_event = test_holder->event;
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break;
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}
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}
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if (!test_event)
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return NULL;
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fsnotify_get_event(test_event);
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/* if they are exactly the same we are done */
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if (test_event->mask == event->mask)
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return test_event;
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/*
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* if the refcnt == 2 this is the only queue
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* for this event and so we can update the mask
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* in place.
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*/
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if (atomic_read(&test_event->refcnt) == 2) {
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test_event->mask |= event->mask;
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return test_event;
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}
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new_event = fsnotify_clone_event(test_event);
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/* done with test_event */
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fsnotify_put_event(test_event);
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/* couldn't allocate memory, merge was not possible */
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if (unlikely(!new_event))
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return ERR_PTR(-ENOMEM);
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/* build new event and replace it on the list */
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new_event->mask = (test_event->mask | event->mask);
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fsnotify_replace_event(test_holder, new_event);
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/* we hold a reference on new_event from clone_event */
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return new_event;
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}
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#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
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static int fanotify_get_response_from_access(struct fsnotify_group *group,
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struct fsnotify_event *event)
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{
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int ret;
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pr_debug("%s: group=%p event=%p\n", __func__, group, event);
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wait_event(group->fanotify_data.access_waitq, event->response ||
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atomic_read(&group->fanotify_data.bypass_perm));
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if (!event->response) /* bypass_perm set */
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return 0;
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/* userspace responded, convert to something usable */
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spin_lock(&event->lock);
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switch (event->response) {
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case FAN_ALLOW:
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ret = 0;
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break;
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case FAN_DENY:
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default:
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ret = -EPERM;
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}
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event->response = 0;
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spin_unlock(&event->lock);
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pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
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group, event, ret);
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return ret;
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}
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#endif
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static int fanotify_handle_event(struct fsnotify_group *group,
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struct fsnotify_mark *inode_mark,
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struct fsnotify_mark *fanotify_mark,
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struct fsnotify_event *event)
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{
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int ret = 0;
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struct fsnotify_event *notify_event = NULL;
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BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
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BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
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BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
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BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
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BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
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BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
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BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
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BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
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BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
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BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
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pr_debug("%s: group=%p event=%p\n", __func__, group, event);
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notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
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if (IS_ERR(notify_event))
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return PTR_ERR(notify_event);
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#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
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if (event->mask & FAN_ALL_PERM_EVENTS) {
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/* if we merged we need to wait on the new event */
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if (notify_event)
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event = notify_event;
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ret = fanotify_get_response_from_access(group, event);
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}
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#endif
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if (notify_event)
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fsnotify_put_event(notify_event);
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return ret;
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}
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static bool fanotify_should_send_event(struct fsnotify_group *group,
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struct inode *to_tell,
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struct fsnotify_mark *inode_mark,
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struct fsnotify_mark *vfsmnt_mark,
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__u32 event_mask, void *data, int data_type)
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{
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__u32 marks_mask, marks_ignored_mask;
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struct path *path = data;
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pr_debug("%s: group=%p to_tell=%p inode_mark=%p vfsmnt_mark=%p "
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"mask=%x data=%p data_type=%d\n", __func__, group, to_tell,
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inode_mark, vfsmnt_mark, event_mask, data, data_type);
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/* if we don't have enough info to send an event to userspace say no */
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if (data_type != FSNOTIFY_EVENT_PATH)
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return false;
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/* sorry, fanotify only gives a damn about files and dirs */
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if (!S_ISREG(path->dentry->d_inode->i_mode) &&
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!S_ISDIR(path->dentry->d_inode->i_mode))
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return false;
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if (inode_mark && vfsmnt_mark) {
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marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
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marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
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} else if (inode_mark) {
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/*
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* if the event is for a child and this inode doesn't care about
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* events on the child, don't send it!
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*/
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if ((event_mask & FS_EVENT_ON_CHILD) &&
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!(inode_mark->mask & FS_EVENT_ON_CHILD))
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return false;
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marks_mask = inode_mark->mask;
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marks_ignored_mask = inode_mark->ignored_mask;
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} else if (vfsmnt_mark) {
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marks_mask = vfsmnt_mark->mask;
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marks_ignored_mask = vfsmnt_mark->ignored_mask;
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} else {
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BUG();
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}
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if (S_ISDIR(path->dentry->d_inode->i_mode) &&
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(marks_ignored_mask & FS_ISDIR))
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return false;
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if (event_mask & marks_mask & ~marks_ignored_mask)
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return true;
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return false;
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}
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static void fanotify_free_group_priv(struct fsnotify_group *group)
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{
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struct user_struct *user;
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user = group->fanotify_data.user;
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atomic_dec(&user->fanotify_listeners);
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free_uid(user);
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}
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const struct fsnotify_ops fanotify_fsnotify_ops = {
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.handle_event = fanotify_handle_event,
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.should_send_event = fanotify_should_send_event,
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.free_group_priv = fanotify_free_group_priv,
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.free_event_priv = NULL,
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.freeing_mark = NULL,
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};
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