From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Date: Fri, 29 Sep 2017 15:22:55 +0000 (+0300)
Subject: block/mirror: check backing in bdrv_mirror_top_flush
X-Git-Tag: v2.11.0-rc0~61^2^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ce960aa9062a407d0ca15aee3dcd3bd84a4e24f9;p=thirdparty%2Fqemu.git

block/mirror: check backing in bdrv_mirror_top_flush

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

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20170929152255.5431-1-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
---

diff --git a/block/mirror.c b/block/mirror.c
index 3b6f0c57722..153758ca9fa 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1041,6 +1041,10 @@ 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);
 }