From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752300AbbCWI1X (ORCPT ); Mon, 23 Mar 2015 04:27:23 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46253 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752239AbbCWI1W (ORCPT ); Mon, 23 Mar 2015 04:27:22 -0400 From: Michal Kubecek Subject: [PATCH net] tcp: prevent fetching dst twice in early demux code To: "David S. Miller" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy Message-Id: <20150323082718.265EDA0BE9@unicorn.suse.cz> Date: Mon, 23 Mar 2015 09:27:18 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On s390x, gcc 4.8 compiles this part of tcp_v6_early_demux() struct dst_entry *dst = sk->sk_rx_dst; if (dst) dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie); to code reading sk->sk_rx_dst twice, once for the test and once for the argument of ip6_dst_check() (dst_check() is inline). This allows ip6_dst_check() to be called with null first argument, causing a crash. Protect sk->sk_rx_dst access by ACCESS_ONCE() both in IPv4 and IPv6 TCP early demux code. Fixes: 41063e9dd119 ("ipv4: Early TCP socket demux.") Fixes: c7109986db3c ("ipv6: Early TCP socket demux") Signed-off-by: Michal Kubecek --- net/ipv4/tcp_ipv4.c | 2 +- net/ipv6/tcp_ipv6.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 5a2dfed..3d42b45 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1518,7 +1518,7 @@ void tcp_v4_early_demux(struct sk_buff *skb) skb->sk = sk; skb->destructor = sock_edemux; if (sk->sk_state != TCP_TIME_WAIT) { - struct dst_entry *dst = sk->sk_rx_dst; + struct dst_entry *dst = ACCESS_ONCE(sk->sk_rx_dst); if (dst) dst = dst_check(dst, 0); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 5d46832..50eb5ff 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1585,7 +1585,7 @@ static void tcp_v6_early_demux(struct sk_buff *skb) skb->sk = sk; skb->destructor = sock_edemux; if (sk->sk_state != TCP_TIME_WAIT) { - struct dst_entry *dst = sk->sk_rx_dst; + struct dst_entry *dst = ACCESS_ONCE(sk->sk_rx_dst); if (dst) dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie); -- 2.3.3