Re: [PATCH net v1] virtio_net: bugfix overflow inside xdp_linearize_page()

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Apr 14, 2023 at 02:08:35PM +0800, Xuan Zhuo wrote:
> Here we copy the data from the original buf to the new page. But we
> not check that it may be overflow.
> 
> As long as the size received(including vnethdr) is greater than 3840
> (PAGE_SIZE -VIRTIO_XDP_HEADROOM). Then the memcpy will overflow.
> 
> And this is completely possible, as long as the MTU is large, such
> as 4096. In our test environment, this will cause crash. Since crash is
> caused by the written memory, it is meaningless, so I do not include it.
> 
> Fixes: 72979a6c3590 ("virtio_net: xdp, add slowpath case for non contiguous buffers")
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Acked-by: Jason Wang <jasowang@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> v1:  add Fixes tag
> 
>  drivers/net/virtio_net.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 2396c28c0122..ea1bd4bb326d 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -814,8 +814,13 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
>  				       int page_off,
>  				       unsigned int *len)
>  {
> -	struct page *page = alloc_page(GFP_ATOMIC);
> +	int tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> +	struct page *page;
> +
> +	if (page_off + *len + tailroom > PAGE_SIZE)
> +		return NULL;
> 
> +	page = alloc_page(GFP_ATOMIC);
>  	if (!page)
>  		return NULL;
> 
> @@ -823,7 +828,6 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
>  	page_off += *len;
> 
>  	while (--*num_buf) {
> -		int tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>  		unsigned int buflen;
>  		void *buf;
>  		int off;
> --
> 2.32.0.3.g01195cf9f