Re: [PATCH net 4/4] virito-net: fix leaking page for gso packet during mergeable XDP

Michael S. Tsirkin
2018-05-21T15:01:39Z

On Mon, May 21, 2018 at 04:35:06PM +0800, Jason Wang wrote:
> We need to drop refcnt to xdp_page if we see a gso packet. Otherwise
> it will be leaked. Fixing this by moving the check of gso packet above
> the linearizing logic.
>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Fixes: 72979a6c3590 ("virtio_net: xdp, add slowpath case for non contiguous buffers")
> Signed-off-by: Jason Wang <jasowang@redhat.com>

typo in subject

> ---
> drivers/net/virtio_net.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 165a922..f8db809 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -707,6 +707,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> void *data;
> u32 act;
>
> + /* Transient failure which in theory could occur if
> + * in-flight packets from before XDP was enabled reach
> + * the receive path after XDP is loaded. In practice I
> + * was not able to create this condition.

BTW we should probably drop the last sentence. It says in theory, should be enough.

> + */
> + if (unlikely(hdr->hdr.gso_type))
> + goto err_xdp;
> +
> /* This happens when rx buffer size is underestimated
> * or headroom is not enough because of the buffer
> * was refilled before XDP is set. This should only
> @@ -728,14 +736,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> xdp_page = page;
> }
>
> - /* Transient failure which in theory could occur if
> - * in-flight packets from before XDP was enabled reach
> - * the receive path after XDP is loaded. In practice I
> - * was not able to create this condition.
> - */
> - if (unlikely(hdr->hdr.gso_type))
> - goto err_xdp;
> -
> /* Allow consuming headroom but reserve enough space to push
> * the descriptor on if we get an XDP_TX return code.
> */
> --
> 2.7.4