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References: <20210809101609.148-1-xieyongji@bytedance.com> <08366773-76b5-be73-7e32-d9ce6f6799bf@redhat.com>
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From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Tue, 10 Aug 2021 12:59:11 +0800
Message-ID: <CACycT3tPR30RU8XmWbDA=Hp-A6BBifd-q_aqrmU-9VK=OaRJRg@mail.gmail.com>
Subject: Re: [PATCH v5] virtio-blk: Add validation for block size in config space
To:     Jason Wang <jasowang@redhat.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        virtualization <virtualization@lists.linux-foundation.org>,
        linux-block@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Tue, Aug 10, 2021 at 11:05 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> =E5=9C=A8 2021/8/9 =E4=B8=8B=E5=8D=886:16, Xie Yongji =E5=86=99=E9=81=93:
> > An untrusted device might presents an invalid block size
> > in configuration space. This tries to add validation for it
> > in the validate callback and clear the VIRTIO_BLK_F_BLK_SIZE
> > feature bit if the value is out of the supported range.
> >
> > And we also double check the value in virtblk_probe() in
> > case that it's changed after the validation.
> >
> > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > ---
> >   drivers/block/virtio_blk.c | 39 +++++++++++++++++++++++++++++++++----=
--
> >   1 file changed, 33 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 4b49df2dfd23..afb37aac09e8 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -692,6 +692,28 @@ static const struct blk_mq_ops virtio_mq_ops =3D {
> >   static unsigned int virtblk_queue_depth;
> >   module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
> >
> > +static int virtblk_validate(struct virtio_device *vdev)
> > +{
> > +     u32 blk_size;
> > +
> > +     if (!vdev->config->get) {
> > +             dev_err(&vdev->dev, "%s failure: config access disabled\n=
",
> > +                     __func__);
> > +             return -EINVAL;
> > +     }
> > +
> > +     if (!virtio_has_feature(vdev, VIRTIO_BLK_F_BLK_SIZE))
> > +             return 0;
> > +
> > +     blk_size =3D virtio_cread32(vdev,
> > +                     offsetof(struct virtio_blk_config, blk_size));
> > +
> > +     if (blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE)
> > +             __virtio_clear_bit(vdev, VIRTIO_BLK_F_BLK_SIZE);
>
>
> I wonder if it's better to just fail here as what we did for probe().
>

Looks like we don't need to do that since we already clear the
VIRTIO_BLK_F_BLK_SIZE to tell the device that we don't use the block
size in configuration space. Just like what we did in
virtnet_validate().

Thanks,
Yongji