[Qemu-devel] Re: [PATCH] qcow2 corruption: Fix alloc_cluster_link_l2

[Consul <void@aleksoft.net>]

Kevin Wolf wrote:
> This patch fixes a qcow2 corruption bug introduced in SVN Rev 5861. L2 tables
> are big endian, so entries must be converted before being passed to functions.
> 

Excellent! I think it is this bug who bit me more than once.
Acked-by: Alex Ivanov <void@aleksoft.net>

> This bug is easy to trigger. The following script will create and destroy a
> qcow2 image (the header is gone after three loop iterations):
> 
>     #!/bin/bash
>     qemu-img create -f qcow2 test.qcow 1M
>     for i in $(seq 1 10); do
>     qemu-system-x86_64 -hda test.qcow -monitor stdio > /dev/null 2>&1 <<EOF
>     savevm test-$i
>     quit
>     EOF
>     done
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block-qcow2.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/block-qcow2.c b/block-qcow2.c
> index da8fb42..985214f 100644
> --- a/block-qcow2.c
> +++ b/block-qcow2.c
> @@ -1007,7 +1007,7 @@ static int alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
>          goto err;
>  
>      for (i = 0; i < j; i++)
> -        free_any_clusters(bs, old_cluster[i], 1);
> +        free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1);
>  
>      ret = 0;
>  err: