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Tsirkin" To: Xuan Zhuo Cc: netdev@vger.kernel.org, Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , virtualization@lists.linux.dev, Si-Wei Liu , Darren Kenny Subject: Re: [PATCH net] virtio-net: fix overflow inside virtnet_rq_alloc Message-ID: <20240820160920-mutt-send-email-mst@kernel.org> References: <20240820071913.68004-1-xuanzhuo@linux.alibaba.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240820071913.68004-1-xuanzhuo@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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" > Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@oracle.com > Signed-off-by: Xuan Zhuo > --- > 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; >From API POV, I don't like it that virtnet_rq_alloc relies on the caller to invoke skb_page_frag_refill. It's better to pass in the length to refill. > @@ -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