linux-kernel - Re: [PATCH] use %pK for /proc/kallsyms and /proc/modules

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Message-ID: <20110127002936.GG4981@outflux.net>
Date:	Wed, 26 Jan 2011 16:29:36 -0800
From:	Kees Cook <kees.cook@...onical.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Tejun Heo <tj@...nel.org>, Marcus Meissner <meissner@...e.de>,
	Jason Wessel <jason.wessel@...driver.com>,
	Eugene Teo <eugeneteo@...nel.org>,
	Joe Perches <joe@...ches.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Len Brown <len.brown@...el.com>,
	Changli Gao <xiaosuo@...il.com>,
	Dan Rosenberg <drosenberg@...curity.com>
Subject: Re: [PATCH] use %pK for /proc/kallsyms and /proc/modules

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@...onical.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
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