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Date: Wed, 21 Jan 2015 15:23:53 +0000
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20150121152353.GC4740@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 11/12] qcow2/overlaps: Protect inactive
	L2 tables
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To: Max Reitz <mreitz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Peter Lieven <pl@kamp.de>, qemu-devel@nongnu.org


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On Mon, Nov 24, 2014 at 04:56:59PM +0100, Max Reitz wrote:
> @@ -136,6 +138,34 @@ int qcow2_read_snapshots(BlockDriverState *bs)
>                                    size_to_clusters(s, sn->l1_size *
>                                                        sizeof(uint64_t)),
>                                    QCOW2_OL_INACTIVE_L1);
> +
> +        if (!(s->overlap_check & QCOW2_OL_INACTIVE_L2)) {
> +            continue;
> +        }
> +
> +        l1_table = qemu_try_blockalign(bs->file,
> +                                       sn->l1_size * sizeof(uint64_t));

At this point we haven't validated sn->l1_size <= QCOW_MAX_L1_SIZE.

A bogus l1_size means we do a huge read and add junk into the metadata
list.  I think it would be best to check the value here.

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