The dev_id returned by the call to blk_get_attached_dev_id() in
blk_root_get_parent_desc() can be NULL (an internal call to
object_get_canonical_path may have returned NULL) so it should
be checked before dereferencing.

Signed-off-by: Liam Merwick <Liam.Merwick@oracle.com>
Reviewed-by: Darren Kenny <Darren.Kenny@oracle.com>
Reviewed-by: Mark Kanda <Mark.Kanda@oracle.com>
---
 block/block-backend.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index fa120630be83..210eee75006a 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -136,7 +136,7 @@ static char *blk_root_get_parent_desc(BdrvChild *child)
     }
 
     dev_id = blk_get_attached_dev_id(blk);
-    if (*dev_id) {
+    if (dev_id && *dev_id) {
         return dev_id;
     } else {
         /* TODO Callback into the BB owner for something more detailed */
-- 
1.8.3.1