Re: [Qemu-devel] [for 3.1? PATCH] qcow2: Assert that refcount block offsets fit in the refcount table

[Eric Blake]

On 11/13/18 10:45 AM, Alberto Garcia wrote:
> Refcount table entries have a field to store the offset of the
> refcount block. The rest of the bits of the entry are currently
> reserved.
>
> The offset is always taken from the entry using REFT_OFFSET_MASK to
> ensure that we only use the bits that belong to that field.
>
> While that mask is used every time we read from the refcount table, it
> is never used when we write to it. Due to the other constraints of the
> qcow2 format QEMU can never produce refcount block offsets that don't
> fit in that field so any such offset when allocating a refcount block
> would indicate a bug in QEMU.
> ---
>   block/qcow2-refcount.c | 3 +++
>   1 file changed, 3 insertions(+)

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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