[Qemu-block] [PATCH] migration/block-dirty-bitmap: fix Coverity CID1390625

[Vladimir Sementsov-Ogievskiy]

Theoretically possible that we finish the skipping loop with bs = NULL
and the following code will crash trying to dereference it. Fix that.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
 migration/block-dirty-bitmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 477826330c..6de808f95f 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -288,6 +288,10 @@ static int init_dirty_bitmap_migration(void)
             bs = backing_bs(bs);
         }
 
+        if (!bs || bs->implicit) {
+            continue;
+        }
+
         for (bitmap = bdrv_dirty_bitmap_next(bs, NULL); bitmap;
              bitmap = bdrv_dirty_bitmap_next(bs, bitmap))
         {
-- 
2.18.0