Re: [PATCH V2 01/12] virtio-blk: validate num_queues during probe

Michael S. Tsirkin
2021-10-13T10:04:52Z

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@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Stefano Garzarella <sgarzare@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

I'd rather fail probe so we don't need to support that.

> ---
> 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