Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S933080AbbFJOti (ORCPT <rfc822;w@1wt.eu>);
	Wed, 10 Jun 2015 10:49:38 -0400
Received: from mail.linuxfoundation.org ([140.211.169.12]:49921 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752623AbbFJOt3 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 10 Jun 2015 10:49:29 -0400
Date: Wed, 10 Jun 2015 07:49:28 -0700
From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: Matthias Schiffer <mschiffer@universe-factory.net>
Cc: Lisa Du <cldu@marvell.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: A race condition between debugfs and seq_file operation
Message-ID: <20150610144928.GA30851@kroah.com>
References: <CAG9bXvm70+hE5qsk1UGCzXn3d6FcDs1AJhjM-Homcsu2OmHt6w@mail.gmail.com>
 <CAG9bXv=xFZfuX26OXA+5Go38+JXbq-rwbhcjnyKdTacerRtCvA@mail.gmail.com>
 <CAG9bXvnTPkD8ZDKNakqzKVuJ+iOETdYj6=R2moTnmdUP=X1YVw@mail.gmail.com>
 <3626bdb18cfc40c98618d0ee68816ab0@SC-EXCH04.marvell.com>
 <20150609211202.GA16801@kroah.com>
 <9473dc801fb245ea8df91da31d426f7f@SC-EXCH04.marvell.com>
 <20150610052023.GA23451@kroah.com>
 <55784305.4040309@universe-factory.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <55784305.4040309@universe-factory.net>
User-Agent: Mutt/1.5.23+89 (0255b37be491) (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2200
Lines: 61

On Wed, Jun 10, 2015 at 04:00:37PM +0200, Matthias Schiffer wrote:
> On 06/10/2015 07:20 AM, gregkh@linuxfoundation.org wrote:
> > On Wed, Jun 10, 2015 at 05:00:03AM +0000, Lisa Du wrote:
> >>> -----Original Message-----
> >>> From: gregkh@linuxfoundation.org [mailto:gregkh@linuxfoundation.org]
> >>> Sent: 2015年6月10日 5:12
> >>> To: Lisa Du
> >>> Cc: linux-kernel@vger.kernel.org
> >>> Subject: Re: A race condition between debugfs and seq_file operation
> >>>
> >>> On Mon, Jun 08, 2015 at 04:28:10AM +0000, Lisa Du wrote:
> >>>> Hi, All
> >>>> Recently I met one race condition related to debugfs.
> >>>>
> >>>> Take an example from ion.c in kernel3.14:
> >>>> static int ion_debug_client_open(struct inode *inode, struct file
> >>>> *file) {
> >>>> 	return single_open(file, ion_debug_client_show, inode->i_private); }
> >>>>
> >>>> static const struct file_operations debug_client_fops = {
> >>>> 	.open = ion_debug_client_open,
> >>>> 	.read = seq_read,
> >>>> 	.llseek = seq_lseek,
> >>>> 	.release = single_release,
> >>>> };
> >>>> client->debug_root = debugfs_create_file(client->display_name, 0664,
> >>>> 					dev->clients_debug_root,
> >>>> 					client, &debug_client_fops);
> >>>>
> >>>> I find during I read the debugfs node, driver can do
> >>>> debugfs_remove_recursive(dentry); Is it expected?
> >>>
> >>> Yes.  Well, not "expected", but a mess, yes.
> >>>
> >>> Removing debugfs files are known to have lots of races, this isn't the only
> >>> one :(
> >> Thanks for the reply! 
> >> Not sure if there is any plan to resolve such races in the future?
> > 
> > Yes, I have "plans", but it's on my very long todo list behind lots of
> > other things...
> > 
> > If you want to look into it, please, that would be wonderful.
> > 
> > thanks,
> > 
> > greg k-h
> 
> I've stumbled across related issues a few days ago (mostly in network
> drivers). What I've found out:

<snip>

Yes, all of these are issues, as I mentioned.

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/