linux-kernel - Re: [PATCH v4] virtio-net: Add validation for used length

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Date:   Tue, 1 Jun 2021 09:51:53 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>, mst@...hat.com,
        kuba@...nel.org
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] virtio-net: Add validation for used length


在 2021/5/31 下午9:58, 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@...edance.com>


Acked-by: Jason Wang <jasowang@...hat.com>


> ---
>   drivers/net/virtio_net.c | 20 +++++++++++++-------
>   1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 073fec4c0df1..ed969b65126e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -730,6 +730,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   	len -= vi->hdr_len;
>   	stats->bytes += len;
>   
> +	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++;
> +		goto err_len;
> +	}
>   	rcu_read_lock();
>   	xdp_prog = rcu_dereference(rq->xdp_prog);
>   	if (xdp_prog) {
> @@ -833,6 +839,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   err_xdp:
>   	rcu_read_unlock();
>   	stats->xdp_drops++;
> +err_len:
>   	stats->drops++;
>   	put_page(page);
>   xdp_xmit:
> @@ -886,6 +893,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>   	head_skb = NULL;
>   	stats->bytes += len - vi->hdr_len;
>   
> +	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;
> +	}
>   	rcu_read_lock();
>   	xdp_prog = rcu_dereference(rq->xdp_prog);
>   	if (xdp_prog) {
> @@ -1012,13 +1025,6 @@ 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;