netdev - Re: [PATCH net-next 1/5] virtio_net: Fix an unsafe reference to the page chain

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Date: Sun, 28 May 2023 02:29:02 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: Liang Chen <liangchen.linux@...il.com>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, xuanzhuo@...ux.alibaba.com,
	kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net,
	pabeni@...hat.com, alexander.duyck@...il.com
Subject: Re: [PATCH net-next 1/5] virtio_net: Fix an unsafe reference to the
 page chain

On Fri, May 26, 2023 at 02:38:54PM +0800, Jason Wang wrote:
> On Fri, May 26, 2023 at 1:46 PM Liang Chen <liangchen.linux@...il.com> wrote:
> >
> > "private" of buffer page is currently used for big mode to chain pages.
> > But in mergeable mode, that offset of page could mean something else,
> > e.g. when page_pool page is used instead. So excluding mergeable mode to
> > avoid such a problem.
> 
> If this issue happens only in the case of page_pool, it would be
> better to squash it there.
> 
> Thanks


This is a tiny patch so I don't care. Generally it's ok
to first rework code then change functionality.
in this case what Jason says os right especially because
you then do not need to explain that current code is ok.

> >
> > Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> > ---
> >  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 5a7f7a76b920..c5dca0d92e64 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -497,7 +497,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >                         return NULL;
> >
> >                 page = (struct page *)page->private;
> > -               if (page)
> > +               if (!vi->mergeable_rx_bufs && page)
> >                         give_pages(rq, page);
> >                 goto ok;
> >         }
> > --
> > 2.31.1
> >