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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: <20240906053922-mutt-send-email-mst@kernel.org> References: <20240820071913.68004-1-xuanzhuo@linux.alibaba.com> <20240906044143-mutt-send-email-mst@kernel.org> <1725612818.815039-1-xuanzhuo@linux.alibaba.com> <20240906045904-mutt-send-email-mst@kernel.org> <1725614736.9464588-1-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: <1725614736.9464588-1-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 Fri, Sep 06, 2024 at 05:25:36PM +0800, Xuan Zhuo wrote: > On Fri, 6 Sep 2024 05:08:56 -0400, "Michael S. Tsirkin" wrote: > > On Fri, Sep 06, 2024 at 04:53:38PM +0800, Xuan Zhuo wrote: > > > On Fri, 6 Sep 2024 04:43:29 -0400, "Michael S. Tsirkin" 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" > > > > > Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@oracle.com > > > > > Signed-off-by: Xuan Zhuo > > > > > > > > > > > > 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. > > > > So what are we doing? Revert the whole pile for now? > > Seems to be a bit of a pity, but maybe that's the best we can do > > for this release. > > @Jason Could you review this? > > I think this problem is clear, though I do not know why it did not work > for Darren. > > Thanks. > No regressions is a hard rule. If we can't figure out the regression now, we should revert and you can try again for the next release. > > > > > > > > > > > > > > > > > --- > > > > > 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 > > > > > >