block: Null pointer dereference in blk_root_get_parent_desc()

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).

Instead of just checking this case before before dereferencing,
adjust blk_get_attached_dev_id() to return the empty string if no
object path can be found (similar to the case when blk->dev is NULL
and an empty string is returned).

Signed-off-by: Liam Merwick <Liam.Merwick@oracle.com>
Message-id: 1541453919-25973-3-git-send-email-Liam.Merwick@oracle.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

diff --git a/block/block-backend.c b/block/block-backend.c
index 2a8f3b55f85fae8e735f2d91beec1c155da81b07..60d37a0c3d414aef721d0fddd121152cc3881367 100644 (file)
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -918,7 +918,8 @@ char *blk_get_attached_dev_id(BlockBackend *blk)
     } else if (dev->id) {
         return g_strdup(dev->id);
     }
-    return object_get_canonical_path(OBJECT(dev));
+
+    return object_get_canonical_path(OBJECT(dev)) ?: g_strdup("");
 }
 
 /*