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

[Jason Wang]

On 2018å05æ21æ 23:01, Michael S. Tsirkin wrote:
> 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@xxxxxxxxx>
> > Fixes: 72979a6c3590 ("virtio_net: xdp, add slowpath case for non contiguous buffers")
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> typo in subject

Let me fix it in V2.

> > ---
> >   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.

Ok.

Thanks

> > +		 */
> > +		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