Commit ffcc89db authored Nov 05, 2014 by Mikulas Patocka Committed by Greg Kroah-Hartman Jan 08, 2015

dm thin: fix a race in thin_dtr



commit 17181fb7a0c3a279196c0eeb2caba65a1519614b upstream.

As long as struct thin_c is in the list, anyone can grab a reference of
it.  Consequently, we must wait for the reference count to drop to zero
*after* we remove the structure from the list, not before.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 2409f513

drivers/md/dm-thin.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -3266,14 +3266,14 @@ static void thin_dtr(struct dm_target *ti)
		struct thin_c *tc = ti->private;
		unsigned long flags;

		thin_put(tc);
		wait_for_completion(&tc->can_destroy);

		spin_lock_irqsave(&tc->pool->lock, flags);
		list_del_rcu(&tc->list);
		spin_unlock_irqrestore(&tc->pool->lock, flags);
		synchronize_rcu();

		thin_put(tc);
		wait_for_completion(&tc->can_destroy);

		mutex_lock(&dm_thin_pool_table.mutex);

		__pool_dec(tc->pool);