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[Qemu-devel] [PULL v2 for-2.0 03/24] qcow2: Check bs->drv in copy_sector


From: Stefan Hajnoczi
Subject: [Qemu-devel] [PULL v2 for-2.0 03/24] qcow2: Check bs->drv in copy_sectors()
Date: Thu, 13 Mar 2014 15:10:47 +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,
 
     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.
-- 
1.8.5.3




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