From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB38CC10F11 for ; Wed, 24 Apr 2019 09:58:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1C7420684 for ; Wed, 24 Apr 2019 09:58:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726728AbfDXJ6P (ORCPT ); Wed, 24 Apr 2019 05:58:15 -0400 Received: from mail-wm1-f66.google.com ([209.85.128.66]:36716 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726181AbfDXJ6P (ORCPT ); Wed, 24 Apr 2019 05:58:15 -0400 Received: by mail-wm1-f66.google.com with SMTP id h18so4140715wml.1 for ; Wed, 24 Apr 2019 02:58:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=2Zbp86JjyFuBqOU2EYOFaP0mhZuLm15njt/F+ecI2WA=; b=mk7VIIumsPhMNJyEDmFesUUD8DKnpDW4tFm24KvqSc4N20ST3SSANdKrdEQ+6mUz/P 45ndDePr5QooW+GWjgK3I3ww2+0t3Dd3Z0Bt6iYlWCGmGbfxNmgDcw0zAsLR2GFo0H/Z CgSMFymjysqInhACtCUVKANoYIjI3sBd4ZeMWYT3WWdKW0/VUKo/xsGzPOMXsBxXA3tF 9v5rVgTpCMhOYcqAv6stzyrHyDigSFOrvNsiMa8XhwWHHHvpJ6U57dHbPiV/PTj2Uqdb NReIVFbDggz5wzKP78xa0krEIaembomsLYWFgg7qCgJqPtPEvv1Ib7g/YzPxDf5AqwIr 3LPg== X-Gm-Message-State: APjAAAVlBxj6B3mQmv3vVQEFMIoUIs5PWW0fcqBvRtmZdfG7dv/sFa1g Eiw2GHmZ4DrT086+XLHcUBGTqg== X-Google-Smtp-Source: APXvYqwO5g8NMmrz+RUJW51+c0xQm39M8zM0T3jZbYn5KrDQntzPmRJMEYH49BXEcBSzvyzaVVSHvg== X-Received: by 2002:a1c:6c09:: with SMTP id h9mr5922939wmc.130.1556099893557; Wed, 24 Apr 2019 02:58:13 -0700 (PDT) Received: from pc-2.home (2a01cb05850ddf00045dd60e6368f84b.ipv6.abo.wanadoo.fr. [2a01:cb05:850d:df00:45d:d60e:6368:f84b]) by smtp.gmail.com with ESMTPSA id i2sm19443499wmg.47.2019.04.24.02.58.12 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 24 Apr 2019 02:58:12 -0700 (PDT) Date: Wed, 24 Apr 2019 11:58:11 +0200 From: Guillaume Nault To: Eric Dumazet Cc: "David S . Miller" , netdev , Eric Dumazet , James Chapman Subject: Re: [PATCH net] l2tp: use rcu_dereference_sk_user_data() in l2tp_udp_encap_recv() Message-ID: <20190424095809.GA17274@pc-2.home> References: <20190423164326.108651-1-edumazet@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190423164326.108651-1-edumazet@google.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Apr 23, 2019 at 09:43:26AM -0700, Eric Dumazet wrote: > Canonical way to fetch sk_user_data from an encap_rcv() handler called > from UDP stack in rcu protected section is to use rcu_dereference_sk_user_data(), > otherwise compiler might read it multiple times. > That reminds me the more general problem we have with ->sk_user_data: https://lore.kernel.org/netdev/20180117.142538.1972806008716856078.davem@davemloft.net/ We're not even guarateed that ->sk_user_data points to a struct l2tp_tunnel (some external modules can still probably override it). There were some locking rules defined for setting ->sk_user_data: https://lore.kernel.org/netdev/20180124203541.3172-3-tom@quantonium.net/ Converting all users to either avoid using ->sk_user_data or using it under the proper pre-conditions has been on my TODO list for a while... I'll try to revive this effort. > Fixes: d00fa9adc528 ("il2tp: fix races with tunnel socket close") ^ Spurious "i". Vi user? :) > Signed-off-by: Eric Dumazet > Cc: James Chapman > --- > net/l2tp/l2tp_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c > index fed6becc5daf86afa2ad9188bb28e151244bb5a6..aee33d1320184e411dbedff72b5bf5199481e53f 100644 > --- a/net/l2tp/l2tp_core.c > +++ b/net/l2tp/l2tp_core.c > @@ -909,7 +909,7 @@ int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb) > { > struct l2tp_tunnel *tunnel; > > - tunnel = l2tp_tunnel(sk); > + tunnel = rcu_dereference_sk_user_data(sk); > if (tunnel == NULL) > goto pass_up; > > -- > 2.21.0.593.g511ec345e18-goog >