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

[Jason Wang <jasowang@redhat.com>]

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@bytedance.com>
> ---
>   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?


> +
>   		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?

And do we need similar check in receive_big()?

Thanks


> +
>   		/* Transient failure which in theory could occur if
>   		 * in-flight packets from before XDP was enabled reach
>   		 * the receive path after XDP is loaded.

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