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

[Michael S. Tsirkin]

On Thu, Apr 03, 2014 at 08:04:23PM +0200, Alexander Graf wrote:
> 
> 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;
> > +    }
> > +

This one causes a warning on 32 bit hosts, will repost a tweaked
version.


> >     switch (opp->model) {
> >     case OPENPIC_MODEL_FSL_MPIC_20:
> >     default:
> > -- 
> > MST
> > 
>