From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756154Ab0IUHYA (ORCPT ); Tue, 21 Sep 2010 03:24:00 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:37439 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754118Ab0IUHX7 (ORCPT ); Tue, 21 Sep 2010 03:23:59 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Kenneth Subject: Re: Problem with debugfs Cc: kosaki.motohiro@jp.fujitsu.com, greg@kroah.com, linux-kernel@vger.kernel.org, Naoya Horiguchi , Andi Kleen , linux-mm In-Reply-To: <20100921061310.GA11526@localhost> References: <20100921022112.GA10336@localhost> <20100921061310.GA11526@localhost> Message-Id: <20100921162316.3C03.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 21 Sep 2010 16:23:56 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Hello, Mr. Greg, > > I'm sorry I had not checked the git before sending my last mail. > > For the problem I mention, consider this scenarios: > > 1. mm/hwpoinson-inject.c create a debugfs file with > debugfs_create_u64("corrupt-filter-flags-mask", ..., > &hwpoison_filter_flags_mask) > 2. hwpoison_filter_flags_mask is supposed to be protected by filp->priv->mutex > of this file when it is accessed from user space. > 3. but when it is accessed from mm/memory-failure.c:hwpoison_filter_flags, > there is no way for the function to protect the operation (so it simply > ignore it). This may create a competition problem. > > It should be a problem. > > I'm sorry from my poor English skill. I think your english is very clear :) Let's cc hwpoison folks. - kosaki > > Best Regards > Kenneth Lee > > On Tue, Sep 21, 2010 at 10:21:12AM +0800, kenny wrote: > > Hi, there, > > > > I do not know who is the maintainer for debugfs now. But I think there is > > problem with its API: It uses filp->priv->mutex to protect the read/write (to > > the file) for the value of its attribute, but the mutex is not exported to the > > API user. Therefore, there is no way to protect its value when you directly > > use the value in your module. > > > > Is my understanding correct? > > > > Thanks > > > > > > Best Regards > > Kenneth Lee > > > -- > 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/