Hi
Here I'm sending backport of patch
17181fb7a0c3a279196c0eeb2caba65a1519614b. It is suitable for stable
branches 3.15 to 3.18.
Mikulas
commit 17181fb7a0c3a279196c0eeb2caba65a1519614b
Author: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Wed Nov 5 17:00:13 2014 -0500
dm thin: fix a race in thin_dtr
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@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 8c5504c..767417a 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3622,14 +3622,14 @@ 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);
--
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