RE: [PATCH net] virtio_net: fix return value check in receive_mergeable()

[wangyunjian]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@xxxxxxxxxx]
> Sent: Monday, December 04, 2017 3:10 PM
> To: wangyunjian <wangyunjian@xxxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx
> Cc: mst@xxxxxxxxxx; caihe <caihe@xxxxxxxxxx>
> Subject: Re: [PATCH net] virtio_net: fix return value check in
> receive_mergeable()
> 
> 
> 
> On 2017å12æ04æ 14:02, wangyunjian wrote:
> > From: Yunjian Wang <wangyunjian@xxxxxxxxxx>
> >
> > The function virtqueue_get_buf_ctx() could return NULL, the return
> > value 'buf' need to be checked with NULL, not value 'ctx'.
> >
> > Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
> > ---
> >   drivers/net/virtio_net.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 19a985e..559b215 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -756,7 +756,7 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> >   		int num_skb_frags;
> >
> >   		buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
> > -		if (unlikely(!ctx)) {
> > +		if (unlikely(!buf)) {
> >   			pr_debug("%s: rx error: %d buffers out of %d
> missing\n",
> >   				 dev->name, num_buf,
> >   				 virtio16_to_cpu(vi->vdev,
> 
> Hi:
> 
> The path looks good but I'm not sure this is a real fix since we add
> data and ctx simultaneously in virtqueue_add_inbuf_ctx().
> 
> Any bad result you see without this patch?
> 

Now no problem has been found yet, and I found it when reviewing the code.

Thanks

> Thanks