On Mon, Dec 13, 2021 at 12:50 PM <mengensun8801@xxxxxxxxx> wrote:
>
> From: mengensun <mengensun@xxxxxxxxxxx>
>
> xdp_linearize_page asume ring elem size is smaller then page size
> when copy the first ring elem, but, there may be a elem size bigger
> then page size.
>
> add_recvbuf_mergeable may add a hole to ring elem, the hole size is
> not sure, according EWMA.
The logic is to try to avoid dropping packets in this case, so I
wonder if it's better to "fix" the add_recvbuf_mergeable().
Or another idea is to switch to use XDP generic here where we can use
skb_linearize() which should be more robust and we can drop the
xdp_linearize_page() logic completely.
Thanks
>
> so, fix it by check copy len,if checked failed, just dropped the
> whole frame, not make the memory dirty after the page.
>
> Signed-off-by: mengensun <mengensun@xxxxxxxxxxx>
> Reviewed-by: MengLong Dong <imagedong@xxxxxxxxxxx>
> Reviewed-by: ZhengXiong Jiang <mungerjiang@xxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 36a4b7c195d5..844bdbd67ff7 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -662,8 +662,12 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
> int page_off,
> unsigned int *len)
> {
> - struct page *page = alloc_page(GFP_ATOMIC);
> + struct page *page;
>
> + if (*len > PAGE_SIZE - page_off)
> + return NULL;
> +
> + page = alloc_page(GFP_ATOMIC);
> if (!page)
> return NULL;
>
> --
> 2.27.0
>
