block: Fix anonymous BBs in blk_root_inactivate()

blk->name isn't an array, but a pointer that can be NULL. Checking for
an anonymous BB must involve a NULL check first, otherwise we get
crashes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>

diff --git a/block/block-backend.c b/block/block-backend.c
index f3a60081a7658bd60adc76a5b2b53ec06953876e..7d7f3697d1aed6ce9d03f9f6cbaf9f2392bda6d0 100644 (file)
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -168,7 +168,7 @@ static int blk_root_inactivate(BdrvChild *child)
      * this point because the VM is stopped) and unattached monitor-owned
      * BlockBackends. If there is still any other user like a block job, then
      * we simply can't inactivate the image. */
-    if (!blk->dev && !blk->name[0]) {
+    if (!blk->dev && !blk_name(blk)[0]) {
         return -EPERM;
     }