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Commit 12703dbf authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
Browse files

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: 5838d444 ("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: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d5bf1418

fs/notify/group.c

+19 −0
Original line number Diff line number Diff line
@@ -39,6 +39,17 @@ static void fsnotify_final_destroy_group(struct fsnotify_group *group) 
	kfree(group);

}



/*

 * Stop queueing new events for this group. Once this function returns

 * fsnotify_add_event() will not add any new events to the group's queue.

 */

void fsnotify_group_stop_queueing(struct fsnotify_group *group)

{

	mutex_lock(&group->notification_mutex);

	group->shutdown = true;

	mutex_unlock(&group->notification_mutex);

}



/*

 * Trying to get rid of a group. Remove all marks, flush all events and release

 * the group reference.
@@ -47,6 +58,14 @@ static void fsnotify_final_destroy_group(struct fsnotify_group *group) 
 */

void fsnotify_destroy_group(struct fsnotify_group *group)

{

	/*

	 * Stop queueing new events. The code below is careful enough to not

	 * require this but fanotify needs to stop queuing events even before

	 * fsnotify_destroy_group() is called and this makes the other callers

	 * of fsnotify_destroy_group() to see the same behavior.

	 */

	fsnotify_group_stop_queueing(group);



	/* clear all inode marks for this group, attach them to destroy_list */

	fsnotify_detach_group_marks(group);

fs/notify/notification.c

+7 −1
Original line number Diff line number Diff line
@@ -82,7 +82,8 @@ void fsnotify_destroy_event(struct fsnotify_group *group, 
 * Add an event to the group notification queue.  The group can later pull this

 * event off the queue to deal with.  The function returns 0 if the event was

 * added to the queue, 1 if the event was merged with some other queued event,

 * 2 if the queue of events has overflown.

 * 2 if the event was not queued - either the queue of events has overflown

 * or the group is shutting down.

 */

int fsnotify_add_event(struct fsnotify_group *group,

		       struct fsnotify_event *event,
@@ -96,6 +97,11 @@ int fsnotify_add_event(struct fsnotify_group *group, 


	mutex_lock(&group->notification_mutex);



	if (group->shutdown) {

		mutex_unlock(&group->notification_mutex);

		return 2;

	}



	if (group->q_len >= group->max_events) {

		ret = 2;

		/* Queue overflow event only if it isn't already queued */

include/linux/fsnotify_backend.h

+3 −0
Original line number Diff line number Diff line
@@ -148,6 +148,7 @@ struct fsnotify_group { 
	#define FS_PRIO_1	1 /* fanotify content based access control */

	#define FS_PRIO_2	2 /* fanotify pre-content access */

	unsigned int priority;

	bool shutdown;		/* group is being shut down, don't queue more events */



	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */

	struct mutex mark_mutex;	/* protect marks_list */
@@ -292,6 +293,8 @@ extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *op 
extern void fsnotify_get_group(struct fsnotify_group *group);

/* drop reference on a group from fsnotify_alloc_group */

extern void fsnotify_put_group(struct fsnotify_group *group);

/* group destruction begins, stop queuing new events */

extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);

/* destroy group */

extern void fsnotify_destroy_group(struct fsnotify_group *group);

/* fasync handler function */