From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261265AbULHRCb (ORCPT ); Wed, 8 Dec 2004 12:02:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261267AbULHRCb (ORCPT ); Wed, 8 Dec 2004 12:02:31 -0500 Received: from fw.osdl.org ([65.172.181.6]:12749 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261265AbULHRCV (ORCPT ); Wed, 8 Dec 2004 12:02:21 -0500 Date: Wed, 8 Dec 2004 09:02:16 -0800 From: Chris Wright To: Andrew Morton Cc: Chris Wright , dave@sr71.net, linux-kernel@vger.kernel.org, Manfred Spraul Subject: Re: oops in proc_pid_stat() on task->real_parent? Message-ID: <20041208090216.N2357@build.pdx.osdl.net> References: <1102467332.19465.197.camel@localhost> <20041207220016.6917ee6f.akpm@osdl.org> <20041207220753.E469@build.pdx.osdl.net> <20041207221821.068568f4.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20041207221821.068568f4.akpm@osdl.org>; from akpm@osdl.org on Tue, Dec 07, 2004 at 10:18:21PM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton (akpm@osdl.org) wrote: > Chris Wright wrote: > > > > * Andrew Morton (akpm@osdl.org) wrote: > > > yup, we fixed that one. > > > > I thought the same thing, but this oops is from proc_pid_stat, not > > proc_pid_status. The code is now in do_task_stat(), and the oops is > > within the orignal tasklist lock (instead of dropping and reaquiring the > > lock). So, might be fixed, but if so, I think for a different reason. > > > > Ah, thanks. > > I'm not sure that the holding of tasklist_lock is going to save us there. > But then, Manfred recently did an audit, so I'm probably missing something. > > Manfred, should we do this? Yeah, I wondered the same. Although I don't see why pid_alive() check would be useful if it's the real_parent that's gone. Dave mentioned that he's got slab poisoning enabled, and the real_parent pointer was valid (i.e. not 6b6b6b6b). So wouldn't tasklist_lock serialize against exiting real_parent? thanks, -chris -- Linux Security Modules http://lsm.immunix.org http://lsm.bkbits.net