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

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Date:   Mon, 29 May 2023 15:25:16 +0800
From:   Liang Chen <liangchen.linux@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.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 Sun, May 28, 2023 at 2:29 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> 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.
>

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

> > >
> > > 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
> > >
>