netdev - Re: [PATCH net] virtio-net: fix overflow inside virtnet_rq

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Message-ID: <1725612818.815039-1-xuanzhuo@linux.alibaba.com>
Date: Fri, 6 Sep 2024 16:53:38 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org,
 Jason Wang <jasowang@...hat.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 virtualization@...ts.linux.dev,
 "Si-Wei Liu" <si-wei.liu@...cle.com>,
 Darren Kenny <darren.kenny@...cle.com>
Subject: Re: [PATCH net] virtio-net: fix overflow inside virtnet_rq_alloc

On Fri, 6 Sep 2024 04:43:29 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Tue, Aug 20, 2024 at 03:19:13PM +0800, Xuan Zhuo wrote:
> > leads to regression on VM with the sysctl value of:
> >
> > - net.core.high_order_alloc_disable=1
> >
> > which could see reliable crashes or scp failure (scp a file 100M in size
> > to VM):
> >
> > The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning
> > of a new frag. When the frag size is larger than PAGE_SIZE,
> > everything is fine. However, if the frag is only one page and the
> > total size of the buffer and virtnet_rq_dma is larger than one page, an
> > overflow may occur. In this case, if an overflow is possible, I adjust
> > the buffer size. If net.core.high_order_alloc_disable=1, the maximum
> > buffer size is 4096 - 16. If net.core.high_order_alloc_disable=0, only
> > the first buffer of the frag is affected.
> >
> > Fixes: f9dac92ba908 ("virtio_ring: enable premapped mode whatever use_dma_api")
> > Reported-by: "Si-Wei Liu" <si-wei.liu@...cle.com>
> > Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@oracle.com
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>
>
> Guys where are we going with this? We have a crasher right now,
> if this is not fixed ASAP I'd have to revert a ton of
> work Xuan Zhuo just did.

I think this patch can fix it and I tested it.
But Darren said this patch did not work.
I need more info about the crash that Darren encountered.

Thanks.

>
>
> > ---
> >  drivers/net/virtio_net.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index c6af18948092..e5286a6da863 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -918,9 +918,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> >  	void *buf, *head;
> >  	dma_addr_t addr;
> >
> > -	if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
> > -		return NULL;
> > -
> >  	head = page_address(alloc_frag->page);
> >
> >  	dma = head;
> > @@ -2421,6 +2418,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
> >  	len = SKB_DATA_ALIGN(len) +
> >  	      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> >
> > +	if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
> > +		return -ENOMEM;
> > +
> >  	buf = virtnet_rq_alloc(rq, len, gfp);
> >  	if (unlikely(!buf))
> >  		return -ENOMEM;
> > @@ -2521,6 +2521,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> >  	 */
> >  	len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
> >
> > +	if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> > +		return -ENOMEM;
> > +
> > +	if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
> > +		len -= sizeof(struct virtnet_rq_dma);
> > +
> >  	buf = virtnet_rq_alloc(rq, len + room, gfp);
> >  	if (unlikely(!buf))
> >  		return -ENOMEM;
> > --
> > 2.32.0.3.g01195cf9f
>