Re: Re: [PATCH] virtio-net: Add validation for used length

[Yongji Xie]

On Wed, May 26, 2021 at 3:52 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> 在 2021/5/25 下午4:45, Yongji Xie 写道:
> > On Tue, May 25, 2021 at 2:30 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
> >>
> >> 在 2021/5/25 下午12:58, Xie Yongji 写道:
> >>> This adds validation for used length (might come
> >>> from an untrusted device) to avoid data corruption
> >>> or loss.
> >>>
> >>> Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
> >>> ---
> >>>    drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
> >>>    1 file changed, 22 insertions(+)
> >>>
> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >>> index c4711e23af88..2dcdc1a3c7e8 100644
> >>> --- a/drivers/net/virtio_net.c
> >>> +++ b/drivers/net/virtio_net.c
> >>> @@ -668,6 +668,13 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >>>                void *orig_data;
> >>>                u32 act;
> >>>
> >>> +             if (unlikely(len > GOOD_PACKET_LEN)) {
> >>> +                     pr_debug("%s: rx error: len %u exceeds max size %lu\n",
> >>> +                              dev->name, len, GOOD_PACKET_LEN);
> >>> +                     dev->stats.rx_length_errors++;
> >>> +                     goto err_xdp;
> >>> +             }
> >>
> >> Need to count vi->hdr_len here?
> >>
> > We did len -= vi->hdr_len before.
>
>
> Right.
>
>
> >
> >>> +
> >>>                if (unlikely(hdr->hdr.gso_type))
> >>>                        goto err_xdp;
> >>>
> >>> @@ -739,6 +746,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >>>        }
> >>>        rcu_read_unlock();
> >>>
> >>> +     if (unlikely(len > GOOD_PACKET_LEN)) {
> >>> +             pr_debug("%s: rx error: len %u exceeds max size %lu\n",
> >>> +                      dev->name, len, GOOD_PACKET_LEN);
> >>> +             dev->stats.rx_length_errors++;
> >>> +             put_page(page);
> >>> +             return NULL;
> >>> +     }
> >>> +
> >>>        skb = build_skb(buf, buflen);
> >>>        if (!skb) {
> >>>                put_page(page);
> >>> @@ -822,6 +837,13 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> >>>                void *data;
> >>>                u32 act;
> >>>
> >>> +             if (unlikely(len > truesize)) {
> >>> +                     pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
> >>> +                              dev->name, len, (unsigned long)ctx);
> >>> +                     dev->stats.rx_length_errors++;
> >>> +                     goto err_xdp;
> >>> +             }
> >>
> >> There's a similar check after the XDP, let's simply move it here?
> > Do we still need that in non-XDP cases?
>
>
> I meant we check once for both XDP and non-XDP if we do it before if
> (xdp_prog)
>

Will do it in v2.

Thanks,
Yongji