From: Kevin Wolf <kwolf@redhat.com>
Date: Thu,  1 Apr 2010 22:48:44 +0200
Message-Id: <1270154924-10400-1-git-send-email-kwolf@redhat.com>
Subject: [Qemu-devel] [PATCH] block: Fix multiwrite error handling
To: qemu-devel@nongnu.org
Cc: kwolf@redhat.com

When two requests of the same multiwrite batch fail, the callback of all
requests in that batch were called twice. This could have any kind of nasty
effects, in my case it lead to use after free and eventually a segfault.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block.c b/block.c
index 31610af..1c36e91 100644
--- a/block.c
+++ b/block.c
@@ -1734,7 +1734,7 @@ static void multiwrite_cb(void *opaque, int ret)
 {
     MultiwriteCB *mcb = opaque;
 
-    if (ret < 0) {
+    if (ret < 0 && !mcb->error) {
         mcb->error = ret;
         multiwrite_user_cb(mcb);
     }
-- 
1.6.6.1