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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E3132C49361 for ; Mon, 21 Jun 2021 08:29:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB06461151 for ; Mon, 21 Jun 2021 08:29:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230302AbhFUIcI (ORCPT ); Mon, 21 Jun 2021 04:32:08 -0400 Received: from mailout1.secunet.com ([62.96.220.44]:57788 "EHLO mailout1.secunet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230137AbhFUIcG (ORCPT ); Mon, 21 Jun 2021 04:32:06 -0400 Received: from cas-essen-01.secunet.de (unknown [10.53.40.201]) by mailout1.secunet.com (Postfix) with ESMTP id 2005D80004E; Mon, 21 Jun 2021 10:29:50 +0200 (CEST) Received: from mbx-essen-01.secunet.de (10.53.40.197) by cas-essen-01.secunet.de (10.53.40.201) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 21 Jun 2021 10:29:49 +0200 Received: from gauss2.secunet.de (10.182.7.193) by mbx-essen-01.secunet.de (10.53.40.197) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 21 Jun 2021 10:29:49 +0200 Received: by gauss2.secunet.de (Postfix, from userid 1000) id 899D131803E8; Mon, 21 Jun 2021 10:29:49 +0200 (CEST) Date: Mon, 21 Jun 2021 10:29:49 +0200 From: Steffen Klassert To: Varad Gautam CC: , linux-rt-users , , Herbert Xu , "David S. Miller" , "Jakub Kicinski" , Florian Westphal , "Ahmed S. Darwish" , Frederic Weisbecker , Subject: Re: [PATCH] xfrm: policy: Restructure RCU-read locking in xfrm_sk_policy_lookup Message-ID: <20210621082949.GX40979@gauss3.secunet.de> References: <20210618141101.18168-1-varad.gautam@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20210618141101.18168-1-varad.gautam@suse.com> X-ClientProxiedBy: cas-essen-02.secunet.de (10.53.40.202) To mbx-essen-01.secunet.de (10.53.40.197) X-EXCLAIMER-MD-CONFIG: 2c86f778-e09b-4440-8b15-867914633a10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 18, 2021 at 04:11:01PM +0200, Varad Gautam wrote: > Commit "xfrm: policy: Read seqcount outside of rcu-read side in > xfrm_policy_lookup_bytype" [Linked] resolved a locking bug in > xfrm_policy_lookup_bytype that causes an RCU reader-writer deadlock on > the mutex wrapped by xfrm_policy_hash_generation on PREEMPT_RT since > 77cc278f7b20 ("xfrm: policy: Use sequence counters with associated > lock"). > > However, xfrm_sk_policy_lookup can still reach xfrm_policy_lookup_bytype > while holding rcu_read_lock(), as: > xfrm_sk_policy_lookup() > rcu_read_lock() > security_xfrm_policy_lookup() > xfrm_policy_lookup() Hm, I don't see that call chain. security_xfrm_policy_lookup() calls a hook with the name xfrm_policy_lookup. The only LSM that has registered a function to that hook is selinux. It registers selinux_xfrm_policy_lookup() and I don't see how we can call xfrm_policy_lookup() from there. Did you actually trigger that bug?