? 2021/5/28 ??8:11, Xie Yongji ??:> This adds validation for used length (might come
> from an untrusted device) to avoid data corruption
> or loss.
>
> Signed-off-by: Xie Yongji <xieyongji at bytedance.com>
> ---
> drivers/net/virtio_net.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 073fec4c0df1..01f15b65824c 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -732,6 +732,17 @@ static struct sk_buff *receive_small(struct net_device
*dev,
>
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> + if (unlikely(len > GOOD_PACKET_LEN)) {
> + pr_debug("%s: rx error: len %u exceeds max size %d\n",
> + dev->name, len, GOOD_PACKET_LEN);
> + dev->stats.rx_length_errors++;
> + if (xdp_prog)
> + goto err_xdp;
> +
> + rcu_read_unlock();
> + put_page(page);
> + return NULL;
> + }
> if (xdp_prog) {
> struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> struct xdp_frame *xdpf;
> @@ -888,6 +899,16 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
>
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> + 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++;
> + if (xdp_prog)
> + goto err_xdp;
> +
> + rcu_read_unlock();
> + goto err_skb;
> + }
Patch looks correct but I'd rather not bother XDP here. It would be
better if we just do the check before rcu_read_lock() and use err_skb
directly() to avoid RCU/XDP stuffs.
Thanks
> if (xdp_prog) {
> struct xdp_frame *xdpf;
> struct page *xdp_page;
> @@ -1012,13 +1033,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
> }
> rcu_read_unlock();
>
> - 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_skb;
> - }
> -
> head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
> metasize, !!headroom);
> curr_skb = head_skb;