Re: [Qemu-devel] [PATCH v4 17/30] openpic: avoid buffer overrun on incoming migration

[Peter Maydell]

On 31 March 2014 15:17, Michael S. Tsirkin <address@hidden> wrote:
> From: Michael Roth <address@hidden>
>
> CVE-2013-4534
>
> opp->nb_cpus is read from the wire and used to determine how many
> IRQDest elements to read into opp->dst[]. If the value exceeds the
> length of opp->dst[], MAX_CPU, opp->dst[] can be overrun with arbitrary
> data from the wire.
>
> Fix this by failing migration if the value read from the wire exceeds
> MAX_CPU.
>
> Signed-off-by: Michael Roth <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>  hw/intc/openpic.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/hw/intc/openpic.c b/hw/intc/openpic.c
> index be76fbd..8cb16da 100644
> --- a/hw/intc/openpic.c
> +++ b/hw/intc/openpic.c
> @@ -1429,6 +1429,9 @@ static int openpic_load(QEMUFile* f, void *opaque, int 
> version_id)
>      qemu_get_be32s(f, &opp->tfrr);
>
>      qemu_get_be32s(f, &opp->nb_cpus);
> +    if (opp->nb_cpus > MAX_CPU) {
> +        return -EINVAL;
> +    }

nb_cpus is a device property so we shouldn't be reading
it off the wire at all. I would suggest treating it as
a "read but ignore value", assuming we care about migration
back-compatibility for this device, or possibly "read and
confirm it matches the value we already have".

thanks
-- PMM