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 S1754546Ab1A0A3t (ORCPT <rfc822;w@1wt.eu>);
	Wed, 26 Jan 2011 19:29:49 -0500
Received: from smtp.outflux.net ([198.145.64.163]:53007 "EHLO smtp.outflux.net"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1754492Ab1A0A3s (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 26 Jan 2011 19:29:48 -0500
Date: Wed, 26 Jan 2011 16:29:36 -0800
From: Kees Cook <kees.cook@canonical.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
        Tejun Heo <tj@kernel.org>, Marcus Meissner <meissner@suse.de>,
        Jason Wessel <jason.wessel@windriver.com>,
        Eugene Teo <eugeneteo@kernel.org>, Joe Perches <joe@perches.com>,
        Bjorn Helgaas <bjorn.helgaas@hp.com>, Len Brown <len.brown@intel.com>,
        Changli Gao <xiaosuo@gmail.com>,
        Dan Rosenberg <drosenberg@vsecurity.com>
Subject: Re: [PATCH] use %pK for /proc/kallsyms and /proc/modules
Message-ID: <20110127002936.GG4981@outflux.net>
References: <20110125181058.GA25670@outflux.net>
 <20110126155706.0188fe02.akpm@linux-foundation.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20110126155706.0188fe02.akpm@linux-foundation.org>
Organization: Canonical
X-HELO: www.outflux.net
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,

On Wed, Jan 26, 2011 at 03:57:06PM -0800, Andrew Morton wrote:
> On Tue, 25 Jan 2011 10:10:58 -0800
> Kees Cook <kees.cook@canonical.com> wrote:
> 
> > Instead of messing with permissions on these files,
> 
> This implies that the patch alters permission handling, only it
> doesn't.  But I worked it out!

Ah yeah, this was related to the earlier attempts to remove the contents
of, or set permissions on, /proc/kallsyms.

> > Note that this changes %x to %p, so some legitimately 0 values in
> > /proc/kallsyms would have changed from 00000000 to "(null)". To avoid
> > this, "(null)" is not used when using the "K" format. Anything parsing
> > such addresses should have no problem with this change. (Thanks to Joe
> > Perches for the suggestion.)
> 
> OK, so what applications did this patch just break?

I'm not aware of any breakage as a result of this yet.

-Kees

-- 
Kees Cook
Ubuntu Security Team