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qcow2: Check bs->drv in copy_sectors()

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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 <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Max Reitz 2014-03-10 23:44:07 +01:00 committed by Stefan Hajnoczi
parent 3456a8d185
commit dba2855572
1 changed files with 4 additions and 0 deletions
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4
block/qcow2-cluster.c
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@ -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.