From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751488AbaJZDGO (ORCPT ); Sat, 25 Oct 2014 23:06:14 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:41813 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750938AbaJZDGM (ORCPT ); Sat, 25 Oct 2014 23:06:12 -0400 Date: Sun, 26 Oct 2014 03:06:08 +0000 From: Al Viro To: "Eric W. Biederman" Cc: Sasha Levin , linux-fsdevel , LKML , Dave Jones Subject: Re: fs: lockup on rename_mutex in fs/dcache.c:1035 Message-ID: <20141026030608.GN7996@ZenIV.linux.org.uk> References: <544C50CB.4090408@oracle.com> <87siibttyi.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87siibttyi.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 25, 2014 at 08:01:41PM -0700, Eric W. Biederman wrote: > Sasha Levin writes: > > > Hi all, > > > > While fuzzing with trinity inside a KVM tools guest running the latest -next > > kernel, I've stumbled on the following spew: > > Weird. I took a quick look and I don't see any changes in d_walk that > in Al's tree or in Linus's kernel for years. > > Has read_seqbegin_or_lock changed somewhere? > > >From a quick reading of the code it simply isn't possible for d_walk to > take the lock twice short of memory corruption. And the fact that the > code has not changed in years seems to suggest it isn't the obvious > cause of d_walk talking the rename_lock twice. It is a fairly obvious case of d_walk() forgetting to drop rename_lock. See upthread for analysis and (hopefully) a fix.