From patchwork Thu Apr 25 22:50:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 1091114 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="p3RiJY4y"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 44qsq90hwNz9s3q for ; Fri, 26 Apr 2019 08:51:00 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727208AbfDYWu4 (ORCPT ); Thu, 25 Apr 2019 18:50:56 -0400 Received: from mail-pf1-f175.google.com ([209.85.210.175]:33458 "EHLO mail-pf1-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725970AbfDYWu4 (ORCPT ); Thu, 25 Apr 2019 18:50:56 -0400 Received: by mail-pf1-f175.google.com with SMTP id h5so670156pfo.0 for ; Thu, 25 Apr 2019 15:50:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:from:subject:cc:message-id:date:user-agent:mime-version :content-language:content-transfer-encoding; bh=N1VNK9zOwP83kFR1DOOO19ZG3v+uT3lsZBQNrxoIfwY=; b=p3RiJY4yHXpbpdqwFvbsvNVWeL92QSsCoL+YTr5Ho+6/p4Huav7Ai7WelOUkLiNHpV yD/T4ZGPWdoxVSXe9F21IrD+5fTYPluPnjCl1aRiC+oSo3YijADwoX1cjQg9Z4jG0b3G hnucDr5SsGqtcPoQeHVNtdbzz49OgMeLGSbCAysNnRwFc9eW0Ve3L4bXPbHMc1/I+9We JOq7dB8ClAE0F9iQ7M0Fff3cIpOAtkAGStJQDUbyvcdfrMgS4/f05GabXqm4d83TKx6i /e1FWppULMQtN4QsziLAKMBGKsXF8TnhP08JNCAnFEomQZ0bTx08ui0dZOuIBzTT3Ea+ pesA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:from:subject:cc:message-id:date:user-agent :mime-version:content-language:content-transfer-encoding; bh=N1VNK9zOwP83kFR1DOOO19ZG3v+uT3lsZBQNrxoIfwY=; b=DGaBzSIyQrEExYsxHkQHV8wSISympGldvC/1zrWFlkP3gAlpaGUKv5EzDe9oc5egwD DIWPyqj5UAxiKYZDxri0Ps9fKL//aI5HgDho9rcHgU+my7tkAd6PHswaCoWBSupfbcdP Zg712tokdIIjGGYk3nxz3txqt6tsjtNdKGxALitIJetRoYztzdWmbyrQh04Ivx3/MsKj E3t73qy9kBRlhImEyH3b6ufClk7SmjA7HvHwlWgldTQIC0yx6azVfrR9t3NgUvC52Ych 593m5sjwnCZ5wGcrxLfafdSogpws1IzfhSwAkT56llRLIqWNljU3h6Zl1rnm98GKS3w9 eJrQ== X-Gm-Message-State: APjAAAXKUsBz3vUuugoAcrXfmgWaYd2i5AAGUj2/tyA0EvXNzja3O+kg r47xQUZ4gCY7ZMofmUiAwuk= X-Google-Smtp-Source: APXvYqxUdia3e+5UAgpay0kunaHiuug/PfI8PIGgz+xcIxWpBjK98ObKoctPYrF41NtZmE+1llqLSA== X-Received: by 2002:a65:5106:: with SMTP id f6mr40335391pgq.253.1556232655712; Thu, 25 Apr 2019 15:50:55 -0700 (PDT) Received: from ?IPv6:2620:15c:2c1:200:55c7:81e6:c7d8:94b? ([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id s198sm7069364pfs.34.2019.04.25.15.50.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Apr 2019 15:50:54 -0700 (PDT) To: Networking From: Eric Dumazet Subject: [RFC] ifa_list needs proper rcu protection Cc: David Ahern , Florian Westphal Message-ID: <7bdc26e6-ce41-02ba-baef-3e4e908f6dd7@gmail.com> Date: Thu, 25 Apr 2019 15:50:53 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 Content-Language: en-US Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It looks that unless RTNL is held, accessing ifa_list needs proper RCU protection ? indev->ifa_list can be changed under us by another cpu (which owns RTNL) Lets took an example. (A proper rcu_dereference() with an happy sparse support would require adding __rcu attribute, I put a READ_ONCE() which should be just fine in this particular context) diff --git a/net/netfilter/nf_nat_redirect.c b/net/netfilter/nf_nat_redirect.c index 78a9e6454ff3d712926397beb904b478b8fab0f1..8619b8d02b0530c5735c31d029f1d79969d979c7 100644 --- a/net/netfilter/nf_nat_redirect.c +++ b/net/netfilter/nf_nat_redirect.c @@ -48,14 +48,17 @@ nf_nat_redirect_ipv4(struct sk_buff *skb, newdst = htonl(0x7F000001); } else { struct in_device *indev; - struct in_ifaddr *ifa; newdst = 0; indev = __in_dev_get_rcu(skb->dev); - if (indev && indev->ifa_list) { - ifa = indev->ifa_list; - newdst = ifa->ifa_local; + if (indev) { + struct in_ifaddr *ifa; + + ifa = READ_ONCE(indev->ifa_list); // rcu_dereference(xxx) + + if (ifa) + newdst = ifa->ifa_local; } if (!newdst)