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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 1D736C433E0 for ; Mon, 8 Jun 2020 04:17:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EDE9120810 for ; Mon, 8 Jun 2020 04:17:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728007AbgFHERi (ORCPT ); Mon, 8 Jun 2020 00:17:38 -0400 Received: from mail.hallyn.com ([178.63.66.53]:35396 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725945AbgFHERg (ORCPT ); Mon, 8 Jun 2020 00:17:36 -0400 Received: by mail.hallyn.com (Postfix, from userid 1001) id 56612E4C; Sun, 7 Jun 2020 23:17:34 -0500 (CDT) Date: Sun, 7 Jun 2020 23:17:34 -0500 From: "Serge E. Hallyn" To: "Paul E. McKenney" Cc: Stephen Rothwell , Amol Grover , James Morris , "Serge E . Hallyn" , linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Joel Fernandes , Madhuparna Bhowmik , linux-security-module@vger.kernel.org Subject: Re: [PATCH RESEND] device_cgroup: Fix RCU list debugging warning Message-ID: <20200608041734.GA10911@mail.hallyn.com> References: <20200406105950.GA2285@workstation-kernel-dev> <20200607062340.7be7e8d5@canb.auug.org.au> <20200607190840.GG4455@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200607190840.GG4455@paulmck-ThinkPad-P72> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 07, 2020 at 12:08:40PM -0700, Paul E. McKenney wrote: > On Sun, Jun 07, 2020 at 06:23:40AM +1000, Stephen Rothwell wrote: > > Hi all, > > > > On Mon, 6 Apr 2020 16:29:50 +0530 Amol Grover wrote: > > > > > > exceptions may be traversed using list_for_each_entry_rcu() > > > outside of an RCU read side critical section BUT under the > > > protection of decgroup_mutex. Hence add the corresponding > > > lockdep expression to fix the following false-positive > > > warning: > > > > > > [ 2.304417] ============================= > > > [ 2.304418] WARNING: suspicious RCU usage > > > [ 2.304420] 5.5.4-stable #17 Tainted: G E > > > [ 2.304422] ----------------------------- > > > [ 2.304424] security/device_cgroup.c:355 RCU-list traversed in non-reader section!! > > > > > > Signed-off-by: Amol Grover > > > --- > > > security/device_cgroup.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/security/device_cgroup.c b/security/device_cgroup.c > > > index 7d0f8f7431ff..b7da9e0970d9 100644 > > > --- a/security/device_cgroup.c > > > +++ b/security/device_cgroup.c > > > @@ -352,7 +352,8 @@ static bool match_exception_partial(struct list_head *exceptions, short type, > > > { > > > struct dev_exception_item *ex; > > > > > > - list_for_each_entry_rcu(ex, exceptions, list) { > > > + list_for_each_entry_rcu(ex, exceptions, list, > > > + lockdep_is_held(&devcgroup_mutex)) { > > > if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) > > > continue; > > > if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) > > > -- > > > 2.24.1 > > > > > > > I have been carrying the above patch in linux-next for some time now. > > I have been carrying it because it fixes problems for syzbot (see the > > third warning in > > https://lore.kernel.org/linux-next/CACT4Y+YnjK+kq0pfb5fe-q1bqe2T1jq_mvKHf--Z80Z3wkyK1Q@mail.gmail.com/). > > Is there some reason it has not been applied to some tree? > > The RCU changes on which this patch depends have long since made it to > mainline, so it can go up any tree. I can take it if no one else will, > but it might be better going in via the security tree. > > Thanx, Paul James, do you mind pulling it in?