From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752570AbbCWOj2 (ORCPT ); Mon, 23 Mar 2015 10:39:28 -0400 Received: from mail-ig0-f179.google.com ([209.85.213.179]:38444 "EHLO mail-ig0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135AbbCWOj1 (ORCPT ); Mon, 23 Mar 2015 10:39:27 -0400 Message-ID: <1427121564.25985.69.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [PATCH net v2] tcp: prevent fetching dst twice in early demux code From: Eric Dumazet To: Michal Kubecek Cc: "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy Date: Mon, 23 Mar 2015 07:39:24 -0700 In-Reply-To: <20150323141400.1568AA0CCC@unicorn.suse.cz> References: <1427118542.25985.62.camel@edumazet-glaptop2.roam.corp.google.com> <20150323141400.1568AA0CCC@unicorn.suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2015-03-23 at 15:14 +0100, Michal Kubecek wrote: > 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 READ_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 > --- Acked-by: Eric Dumazet Thanks Michal