From: Mikulas Patocka Date: Wed, 5 Nov 2014 22:00:13 +0000 (-0500) Subject: dm thin: fix a race in thin_dtr X-Git-Tag: v3.16.35~3216 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ec08e40bf044261a26ab53602d8a8c96a285da88;p=thirdparty%2Fkernel%2Fstable.git 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 Signed-off-by: Mike Snitzer Signed-off-by: Luis Henriques --- diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index df898e0db4195..6f75083a81cc0 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -3183,14 +3183,14 @@ 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);