Re: [Qemu-devel] [PATCH v5 14/24] openpic: avoid buffer overrun on incoming migration

[Alexander Graf]

On 03.04.2014, at 18:51, 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>

Reviewed-by: Alexander Graf <address@hidden>

Though I don't think the nb_cpus checks are necessary, it's always nice to be 
safe rather than sorry :).


Alex

> ---
> hw/intc/openpic.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/openpic.c b/hw/intc/openpic.c
> index be76fbd..e63ccf2 100644
> --- a/hw/intc/openpic.c
> +++ b/hw/intc/openpic.c
> @@ -1416,7 +1416,7 @@ static void openpic_load_IRQ_queue(QEMUFile* f, 
> IRQQueue *q)
> static int openpic_load(QEMUFile* f, void *opaque, int version_id)
> {
>     OpenPICState *opp = (OpenPICState *)opaque;
> -    unsigned int i;
> +    unsigned int i, nb_cpus;
> 
>     if (version_id != 1) {
>         return -EINVAL;
> @@ -1428,7 +1428,11 @@ static int openpic_load(QEMUFile* f, void *opaque, int 
> version_id)
>     qemu_get_be32s(f, &opp->spve);
>     qemu_get_be32s(f, &opp->tfrr);
> 
> -    qemu_get_be32s(f, &opp->nb_cpus);
> +    qemu_get_be32s(f, &nb_cpus);
> +    if (opp->nb_cpus != nb_cpus) {
> +        return -EINVAL;
> +    }
> +    assert(nb_cpus > 0 && nb_cpus <= MAX_CPU);
> 
>     for (i = 0; i < opp->nb_cpus; i++) {
>         qemu_get_sbe32s(f, &opp->dst[i].ctpr);
> @@ -1567,6 +1571,12 @@ static void openpic_realize(DeviceState *dev, Error 
> **errp)
>         {NULL}
>     };
> 
> +    if (opp->nb_cpus > MAX_CPU) {
> +        error_set(errp, QERR_PROPERTY_VALUE_OUT_OF_RANGE,
> +                  TYPE_OPENPIC, "nb_cpus", 0, MAX_CPU);
> +        return;
> +    }
> +
>     switch (opp->model) {
>     case OPENPIC_MODEL_FSL_MPIC_20:
>     default:
> -- 
> MST
>