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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 C20BFC43381 for ; Fri, 1 Mar 2019 09:08:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88E3820851 for ; Fri, 1 Mar 2019 09:08:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733102AbfCAJIe (ORCPT ); Fri, 1 Mar 2019 04:08:34 -0500 Received: from mail.cn.fujitsu.com ([183.91.158.132]:12498 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727951AbfCAJIb (ORCPT ); Fri, 1 Mar 2019 04:08:31 -0500 X-IronPort-AV: E=Sophos;i="5.58,427,1544457600"; d="scan'208";a="55605169" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 01 Mar 2019 17:08:28 +0800 Received: from G08CNEXCHPEKD03.g08.fujitsu.local (unknown [10.167.33.85]) by cn.fujitsu.com (Postfix) with ESMTP id 0FBCC4C4FFEA; Fri, 1 Mar 2019 17:08:14 +0800 (CST) Received: from [10.167.226.33] (10.167.226.33) by G08CNEXCHPEKD03.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server (TLS) id 14.3.408.0; Fri, 1 Mar 2019 17:08:26 +0800 Subject: Re: [PATCH] netfilter: nf_ct_helper: Fix possible panic when nf_conntrack_helper_unregister is used in an unloadable module To: Sergei Shtylyov , Su Yanjun , , , , , , , , References: <1551419766-1039-1-git-send-email-suyanjun218@163.com> From: "Su Yanjun " Message-ID: Date: Fri, 1 Mar 2019 17:08:23 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.167.226.33] X-yoursite-MailScanner-ID: 0FBCC4C4FFEA.A3A41 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: suyj.fnst@cn.fujitsu.com Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/3/1 16:43, Sergei Shtylyov wrote: > Hello! > > On 01.03.2019 8:56, Su Yanjun wrote: > >> From: Su Yanjun >> >> Because nf_conntrack_helper_unregister maybe used in an unloadable >> module, >> it uses 'synchronize_rcu' which may cause kernel panic. >> >> According to the artical: > >    Article? > I got it. >> RCU and Unloadable Modules >> https://lwn.net/Articles/217484/ >> >> When we have a heavy rcu callback load, then some of the callbacks >> might be >> deferred in order to allow other processing to proceed. >> sychnorize_rcu does >> not wait rcu callback complete and module may be unloaded before >> callback >> done. >> >> This patch uses rcu_barrier instead of synchronize_rcu will prevent this >                                                         ^ that/which > missed? > Yes. >> situation. >> >> Signed-off-by: Su Yanjun > [...] > > MBR, Sergei > > Thanks. Su