From dba2855572c746836ad90ce9154403b5929d996b Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Mon, 10 Mar 2014 23:44:07 +0100 Subject: qcow2: Check bs->drv in copy_sectors() Before dereferencing bs->drv for a call to its member bdrv_co_readv(), copy_sectors() should check whether that pointer is indeed valid, since it may have been set to NULL by e.g. a concurrent write triggering the corruption prevention mechanism. Signed-off-by: Max Reitz Signed-off-by: Stefan Hajnoczi --- block/qcow2-cluster.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'block/qcow2-cluster.c') diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 36c1bed350..9499df9ef2 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -380,6 +380,10 @@ static int coroutine_fn copy_sectors(BlockDriverState *bs, BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); + if (!bs->drv) { + return -ENOMEDIUM; + } + /* Call .bdrv_co_readv() directly instead of using the public block-layer * interface. This avoids double I/O throttling and request tracking, * which can lead to deadlock when block layer copy-on-read is enabled. -- cgit v1.2.3