On Wed, Oct 13, 2021 at 6:04 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Tue, Oct 12, 2021 at 02:52:16PM +0800, Jason Wang wrote:
> > If an untrusted device neogitates BLK_F_MQ but advertises a zero
> > num_queues, the driver may end up trying to allocating zero size
> > buffers where ZERO_SIZE_PTR is returned which may pass the checking
> > against the NULL. This will lead unexpected results.
> >
> > Fixing this by using single queue if num_queues is zero.
> >
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > Cc: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> > Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
>
> I'd rather fail probe so we don't need to support that.
I think we should be consistent among all virtio drivers.
E.g without this patch, we stick to 1 if virtio_create_feature() fail.
Do we need to fix that?
And we do something similar at least for the virtio-net and a lot of
other places.
/* We need at least 2 queue's */
if (err || max_queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
max_queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX ||
!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
max_queue_pairs = 1;
Thanks
>
> > ---
> > drivers/block/virtio_blk.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 9b3bd083b411..9deff01a38cb 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -495,7 +495,8 @@ static int init_vq(struct virtio_blk *vblk)
> > err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
> > struct virtio_blk_config, num_queues,
> > &num_vqs);
> > - if (err)
> > + /* We need at least one virtqueue */
> > + if (err || !num_vqs)
> > num_vqs = 1;
> >
> > num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
> > --
> > 2.25.1
>
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