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Miller" , Jakub Kicinski Cc: netdev , Eric Dumazet , Eric Dumazet , Guenter Roeck , Xuan Zhuo , Jason Wang , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org Subject: [PATCH net-next] virtio-net: restrict build_skb() use to some arches Date: Tue, 20 Apr 2021 13:01:44 -0700 Message-Id: <20210420200144.4189597-1-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.31.1.368.gbe11c130af-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet build_skb() is supposed to be followed by skb_reserve(skb, NET_IP_ALIGN), so that IP headers are word-aligned. (Best practice is to reserve NET_IP_ALIGN+NET_SKB_PAD, but the NET_SKB_PAD part is only a performance optimization if tunnel encaps are added.) Unfortunately virtio_net has not provisioned this reserve. We can only use build_skb() for arches where NET_IP_ALIGN == 0 We might refine this later, with enough testing. Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom") Signed-off-by: Eric Dumazet Reported-by: Guenter Roeck Cc: Xuan Zhuo Cc: Jason Wang Cc: "Michael S. Tsirkin" Cc: virtualization@lists.linux-foundation.org --- 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 2e28c04aa6351d2b4016f7d277ce104c4970069d..74d2d49264f3f3b7039be70331d4a44c53b8cc28 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -416,7 +416,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); - if (len > GOOD_COPY_LEN && tailroom >= shinfo_size) { + if (!NET_IP_ALIGN && len > GOOD_COPY_LEN && tailroom >= shinfo_size) { skb = build_skb(p, truesize); if (unlikely(!skb)) return NULL; -- 2.31.1.368.gbe11c130af-goog