Re: [Qemu-devel] [PATCH] qcow2: Assert that L2 table offsets fit in the L1 table

[Eric Blake]

On 2/8/19 9:44 AM, Alberto Garcia wrote:
> L1 table entries have a field to store the offset of an L2 table.
> The rest of the bits of the entry are currently reserved except from
> bit 63, which stores the COPIED flag.
> 
> The offset is always taken from the entry using L1E_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 L1 table, it is
> never used when we write to it. Due to the limits set elsewhere in the
> code QEMU can never produce L2 table offsets that don't fit in that
> field so any such offset when allocating an L2 table would indicate a
> bug in QEMU.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block/qcow2-cluster.c | 3 +++
>  1 file changed, 3 insertions(+)

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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