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Re: [Qemu-devel] [PATCH 1/6] qcow2: Avoid overflow in alloc_clusters_nor


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH 1/6] qcow2: Avoid overflow in alloc_clusters_noref()
Date: Wed, 30 Apr 2014 14:45:46 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Am 29.04.2014 um 19:03 hat Max Reitz geschrieben:
> alloc_clusters_noref() stores the cluster index in a uint64_t. However,
> offsets are often represented as int64_t (as for example the return
> value of alloc_clusters_noref() itself demonstrates). Therefore, we
> should make sure all offsets in the allocated range of clusters are
> representable using int64_t without overflows.
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>  block/qcow2-refcount.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index a37ee45..e6fc30e 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -653,6 +653,13 @@ retry:
>              goto retry;
>          }
>      }
> +
> +    /* Make sure that all offsets in the "allocated" range are representable
> +     * in an int64_t */
> +    if (s->free_cluster_index - 1 > (INT64_MAX >> s->cluster_bits)) {
> +        return -E2BIG;
> +    }

I think you mean EFBIG (File too large) rather than E2BIG (Argument list
too long). I'll fix this while applying.

Kevin



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