From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net] ip: fix csum_sub() with csum_block_sub() Date: Thu, 8 Nov 2018 14:04:07 -0800 Message-ID: <20181108220407.17691-1-xiyou.wangcong@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Cong Wang , Paolo Abeni , Eric Dumazet , Willem de Bruijn To: netdev@vger.kernel.org Return-path: Received: from mail-pf1-f194.google.com ([209.85.210.194]:43115 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729735AbeKIHlq (ORCPT ); Fri, 9 Nov 2018 02:41:46 -0500 Received: by mail-pf1-f194.google.com with SMTP id g7-v6so7660391pfo.10 for ; Thu, 08 Nov 2018 14:04:17 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: When subtracting the checksum of a block of data, csum_block_sub() must be used to respect the offset. We learned this lesson from both commit d55bef5059dd ("net: fix pskb_trim_rcsum_slow() with odd trim offset") and commit d48051c5b837 ("net/mlx5e: fix csum adjustments caused by RXFCS"). Fixes: ca4ef4574f1e ("ip: fix IP_CHECKSUM handling") Cc: Paolo Abeni Cc: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: Cong Wang --- net/ipv4/ip_sockglue.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index fffcc130900e..0d69f0823c08 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -122,7 +122,10 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb, if (offset != 0) { int tend_off = skb_transport_offset(skb) + tlen; - csum = csum_sub(csum, skb_checksum(skb, tend_off, offset, 0)); + + csum = csum_block_sub(csum, + skb_checksum(skb, tend_off, offset, 0), + tend_off); } put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum); -- 2.19.1