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[Qemu-devel] [PULL 03/24] qcow2: Check bs->drv in copy_sectors()

From: Stefan Hajnoczi
Subject: [Qemu-devel] [PULL 03/24] qcow2: Check bs->drv in copy_sectors()
Date: Wed, 12 Mar 2014 11:29:11 +0100

From: Max Reitz <address@hidden>

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 <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
 block/qcow2-cluster.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 36c1bed..9499df9 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -380,6 +380,10 @@ static int coroutine_fn copy_sectors(BlockDriverState *bs,
+    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.

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