From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932677AbcERQFX (ORCPT <rfc822;w@1wt.eu>);
	Wed, 18 May 2016 12:05:23 -0400
Received: from mail.linuxfoundation.org ([140.211.169.12]:35004 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932410AbcERQFV (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 18 May 2016 12:05:21 -0400
Date: Wed, 18 May 2016 09:05:20 -0700
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: Nicolai Stange <nicstange@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jonathan Corbet <corbet@lwn.net>, Jan Kara <jack@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Julia Lawall <Julia.Lawall@lip6.fr>,
        Gilles Muller <Gilles.Muller@lip6.fr>,
        Nicolas Palix <nicolas.palix@imag.fr>, Michal Marek <mmarek@suse.com>,
        linux-kernel@vger.kernel.org, cocci@systeme.lip6.fr
Subject: Re: [PATCH v6 2/8] debugfs: prevent access to removed files' private
 data
Message-ID: <20160518160520.GA5407@kroah.com>
References: <1458652280-19785-1-git-send-email-nicstange@gmail.com>
 <1458652280-19785-3-git-send-email-nicstange@gmail.com>
 <573C80C8.6090307@oracle.com>
 <87r3czxvea.fsf@gmail.com>
 <573C87B8.902@oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <573C87B8.902@oracle.com>
User-Agent: Mutt/1.6.1 (2016-04-27)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, May 18, 2016 at 11:18:16AM -0400, Sasha Levin wrote:
> On 05/18/2016 11:01 AM, Nicolai Stange wrote:
> > Thanks a million for reporting!
> > 
> > 1.) Do you have lockdep enabled?
> 
> Yup, nothing there.
> 
> > 2.) Does this happen before or after userspace init has been spawned,
> >     i.e. does the lockup happen at debugfs file creation time or
> >     possibly at usage time?
> 
> So I looked closer, and it seems to happen after starting syzkaller, which
> as far as I know tries to open many different debugfs files.
> 
> Is there debug code I can add it that'll help us figure out what's up?

Trying to figure out _which_ debugfs file is causing this would be
great, if at all possible.  strace?