[Qemu-stable] [PATCH 03/55] block/mirror: check backing in bdrv_mirror_top_flush

[Michael Roth]

From: Vladimir Sementsov-Ogievskiy <address@hidden>

Backing may be zero after failed bdrv_append in mirror_start_job,
which leads to SIGSEGV.

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Message-id: address@hidden
Signed-off-by: Max Reitz <address@hidden>
(cherry picked from commit ce960aa9062a407d0ca15aee3dcd3bd84a4e24f9)
Signed-off-by: Michael Roth <address@hidden>
---
 block/mirror.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/mirror.c b/block/mirror.c
index 429751b9fe..03fc6d63b7 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1056,6 +1056,10 @@ static int coroutine_fn 
bdrv_mirror_top_pwritev(BlockDriverState *bs,
 
 static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
 {
+    if (bs->backing == NULL) {
+        /* we can be here after failed bdrv_append in mirror_start_job */
+        return 0;
+    }
     return bdrv_co_flush(bs->backing->bs);
 }
 
-- 
2.11.0