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From:   Liang Chen <liangchen.linux@gmail.com>
Date:   Mon, 29 May 2023 15:25:16 +0800
Message-ID: <CAKhg4tL1fkb8JR5+XH_toVDx_c79uH4-fXv8XTDe4gpOFc92VA@mail.gmail.com>
Subject: Re: [PATCH net-next 1/5] virtio_net: Fix an unsafe reference to the
 page chain
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Jason Wang <jasowang@redhat.com>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, xuanzhuo@linux.alibaba.com,
        kuba@kernel.org, edumazet@google.com, davem@davemloft.net,
        pabeni@redhat.com, alexander.duyck@gmail.com
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On Sun, May 28, 2023 at 2:29=E2=80=AFPM Michael S. Tsirkin <mst@redhat.com>=
 wrote:
>
> On Fri, May 26, 2023 at 02:38:54PM +0800, Jason Wang wrote:
> > On Fri, May 26, 2023 at 1:46=E2=80=AFPM Liang Chen <liangchen.linux@gma=
il.com> wrote:
> > >
> > > "private" of buffer page is currently used for big mode to chain page=
s.
> > > 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.
>

Sure. it will be squashed into the page pool enablement patch. Thanks!

> > >
> > > Signed-off-by: Liang Chen <liangchen.linux@gmail.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 =3D (struct page *)page->private;
> > > -               if (page)
> > > +               if (!vi->mergeable_rx_bufs && page)
> > >                         give_pages(rq, page);
> > >                 goto ok;
> > >         }
> > > --
> > > 2.31.1
> > >
>