[dm-devel] [PATCH] dm-thin: Fix deadlock with unknown device id

[Mikulas Patocka]

dm-thin: Fix deadlock with unknown device id

If dm-thin device is created with unknown device id, the code calls
dm_put(pool_md) twice. As a consequence, the reference count underflows
and causes deadlock on device removal.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 drivers/md/dm-thin.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-3.0-fast/drivers/md/dm-thin.c
===================================================================
--- linux-3.0-fast.orig/drivers/md/dm-thin.c	2011-08-04 17:31:16.000000000 +0200
+++ linux-3.0-fast/drivers/md/dm-thin.c	2011-08-04 17:31:26.000000000 +0200
@@ -2031,7 +2031,6 @@ static int thin_ctr(struct dm_target *ti
 		goto bad_pool_lookup;
 	}
 	pool_inc(tc->pool);
-	dm_put(pool_md);
 
 	r = dm_pool_open_thin_device(tc->pool->pmd, tc->dev_id, &tc->td);
 	if (r) {
@@ -2044,6 +2043,8 @@ static int thin_ctr(struct dm_target *ti
 	ti->num_discard_requests = 0;
 	ti->discards_supported = 0;
 
+	dm_put(pool_md);
+
 	return 0;
 
 bad_thin_open: