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Tsirkin" , Jakub Kicinski , virtualization , netdev@vger.kernel.org, linux-kernel References: <20210528121157.105-1-xieyongji@bytedance.com> <49ab3d41-c5d8-a49d-3ff4-28ebfdba0181@redhat.com> From: Jason Wang Message-ID: <4ff90e78-0c7a-def6-ef84-367bcce4cea5@redhat.com> Date: Mon, 31 May 2021 15:51:18 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/5/31 下午3:19, Yongji Xie 写道: > On Mon, May 31, 2021 at 2:49 PM Jason Wang wrote: >> >> 在 2021/5/28 下午8:11, Xie Yongji 写道: >>> This adds validation for used length (might come >>> from an untrusted device) to avoid data corruption >>> or loss. >>> >>> Signed-off-by: Xie Yongji >>> --- >>> drivers/net/virtio_net.c | 28 +++++++++++++++++++++------- >>> 1 file changed, 21 insertions(+), 7 deletions(-) >>> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >>> index 073fec4c0df1..01f15b65824c 100644 >>> --- a/drivers/net/virtio_net.c >>> +++ b/drivers/net/virtio_net.c >>> @@ -732,6 +732,17 @@ static struct sk_buff *receive_small(struct net_device *dev, >>> >>> rcu_read_lock(); >>> xdp_prog = rcu_dereference(rq->xdp_prog); >>> + if (unlikely(len > GOOD_PACKET_LEN)) { >>> + pr_debug("%s: rx error: len %u exceeds max size %d\n", >>> + dev->name, len, GOOD_PACKET_LEN); >>> + dev->stats.rx_length_errors++; >>> + if (xdp_prog) >>> + goto err_xdp; >>> + >>> + rcu_read_unlock(); >>> + put_page(page); >>> + return NULL; >>> + } >>> if (xdp_prog) { >>> struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset; >>> struct xdp_frame *xdpf; >>> @@ -888,6 +899,16 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, >>> >>> rcu_read_lock(); >>> xdp_prog = rcu_dereference(rq->xdp_prog); >>> + if (unlikely(len > truesize)) { >>> + pr_debug("%s: rx error: len %u exceeds truesize %lu\n", >>> + dev->name, len, (unsigned long)ctx); >>> + dev->stats.rx_length_errors++; >>> + if (xdp_prog) >>> + goto err_xdp; >>> + >>> + rcu_read_unlock(); >>> + goto err_skb; >>> + } >> >> Patch looks correct but I'd rather not bother XDP here. It would be >> better if we just do the check before rcu_read_lock() and use err_skb >> directly() to avoid RCU/XDP stuffs. >> > If so, we will miss the statistics of xdp_drops. Is it OK? It should be ok, we still had drops and it was dropped before dealing with XDP. The motivation is to have simple codes. Thanks > > Thanks, > Yongji >