From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967220AbdD0Xlz (ORCPT ); Thu, 27 Apr 2017 19:41:55 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:38136 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965022AbdD0Xlq (ORCPT ); Thu, 27 Apr 2017 19:41:46 -0400 MIME-Version: 1.0 In-Reply-To: References: From: Cong Wang Date: Thu, 27 Apr 2017 16:41:24 -0700 Message-ID: Subject: Re: Boot regression caused by kauditd To: Paul Moore Cc: LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 27, 2017 at 3:38 PM, Paul Moore wrote: > On Thu, Apr 27, 2017 at 5:45 PM, Cong Wang wrote: >> On Thu, Apr 27, 2017 at 2:35 PM, Cong Wang wrote: >>> On Thu, Apr 27, 2017 at 1:31 PM, Cong Wang wrote: >>>> On Wed, Apr 26, 2017 at 2:20 PM, Paul Moore wrote: >>>>> Thanks for the report, this is the only one like it that I've seen. >>>>> I'm looking at the code in Linus' tree and I'm not seeing anything >>>>> obvious ... looking at the trace above it appears that the problem is >>>>> when get_net() goes to bump the refcount and the passed net pointer is >>>>> NULL; unless I'm missing something, the only way this would happen in >>>>> kauditd_thread() is if the auditd_conn.pid value is non-zero but the >>>>> auditd_conn.net pointer is NULL. >>>>> >>>>> That shouldn't happen. >>>>> >>>> >>>> Looking at the code that reads/writes the global auditd_conn, >>>> I don't see how it even works with RCU+spinlock, RCU plays >>>> with pointers and you have to make a copy as its name implies. >>>> But it looks like you simply use RCU+spinlock as a traditional >>>> rwlock, it doesn't work. >>> >>> The attached patch seems working for me, I tried to boot my >>> VM for 4 times, so far no crash or warning. >>> >> >> Or even better, save a memory allocation for reset path... > > I need to step away from my laptop for the evening so I can't give > this a proper review until tomorrow (sending patches as attachments > makes it difficult to review), but on quick glance I did notice a few > small things I would like to see changed. However, since there is no > normal commit description and sign-off, I'm guessing you sent these > out as a suggestion and not a proper patch submission, yes/no? If > that's the case, I'll work up a proper fix tomorrow and share it with > you for comment/review, but if you were planning on sending a proper > patch let me know and I'll wait until I see something in my inbox from > you. I want you to give it sanity check before I submit a formal one. ;) If you don't reject it, I will send a formal one with description and SoB. Thanks.