blkdebug: Delete BH in bdrv_aio_cancel

Otherwise error_callback_bh will access the already released acb.

Cc: qemu-stable@nongnu.org
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/blkdebug.c

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 95b7244..69b330e 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -453,6 +453,10 @@
 static void blkdebug_aio_cancel(BlockDriverAIOCB *blockacb)
 {
     BlkdebugAIOCB *acb = container_of(blockacb, BlkdebugAIOCB, common);
+    if (acb->bh) {
+        qemu_bh_delete(acb->bh);
+        acb->bh = NULL;
+    }
     qemu_aio_release(acb);
 }