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fsnotify: add a way to stop queueing events on group shutdown
Implement a function that can be called when a group is being shutdown
to stop queueing new events to the group. Fanotify will use this.
Fixes: 5838d4442b
("fanotify: fix double free of pending permission events")
Link: http://lkml.kernel.org/r/1473797711-14111-2-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
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@ -39,6 +39,17 @@ static void fsnotify_final_destroy_group(struct fsnotify_group *group)
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kfree(group);
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}
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/*
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* Stop queueing new events for this group. Once this function returns
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* fsnotify_add_event() will not add any new events to the group's queue.
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*/
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void fsnotify_group_stop_queueing(struct fsnotify_group *group)
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{
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mutex_lock(&group->notification_mutex);
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group->shutdown = true;
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mutex_unlock(&group->notification_mutex);
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}
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/*
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* Trying to get rid of a group. Remove all marks, flush all events and release
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* the group reference.
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@ -47,6 +58,14 @@ static void fsnotify_final_destroy_group(struct fsnotify_group *group)
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*/
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void fsnotify_destroy_group(struct fsnotify_group *group)
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{
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/*
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* Stop queueing new events. The code below is careful enough to not
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* require this but fanotify needs to stop queuing events even before
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* fsnotify_destroy_group() is called and this makes the other callers
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* of fsnotify_destroy_group() to see the same behavior.
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*/
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fsnotify_group_stop_queueing(group);
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/* clear all inode marks for this group, attach them to destroy_list */
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fsnotify_detach_group_marks(group);
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@ -82,7 +82,8 @@ void fsnotify_destroy_event(struct fsnotify_group *group,
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* Add an event to the group notification queue. The group can later pull this
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* event off the queue to deal with. The function returns 0 if the event was
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* added to the queue, 1 if the event was merged with some other queued event,
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* 2 if the queue of events has overflown.
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* 2 if the event was not queued - either the queue of events has overflown
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* or the group is shutting down.
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*/
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int fsnotify_add_event(struct fsnotify_group *group,
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struct fsnotify_event *event,
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@ -96,6 +97,11 @@ int fsnotify_add_event(struct fsnotify_group *group,
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mutex_lock(&group->notification_mutex);
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if (group->shutdown) {
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mutex_unlock(&group->notification_mutex);
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return 2;
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}
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if (group->q_len >= group->max_events) {
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ret = 2;
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/* Queue overflow event only if it isn't already queued */
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@ -148,6 +148,7 @@ struct fsnotify_group {
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#define FS_PRIO_1 1 /* fanotify content based access control */
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#define FS_PRIO_2 2 /* fanotify pre-content access */
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unsigned int priority;
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bool shutdown; /* group is being shut down, don't queue more events */
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/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
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struct mutex mark_mutex; /* protect marks_list */
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@ -292,6 +293,8 @@ extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *op
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extern void fsnotify_get_group(struct fsnotify_group *group);
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/* drop reference on a group from fsnotify_alloc_group */
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extern void fsnotify_put_group(struct fsnotify_group *group);
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/* group destruction begins, stop queuing new events */
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extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
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/* destroy group */
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extern void fsnotify_destroy_group(struct fsnotify_group *group);
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/* fasync handler function */
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