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

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Date:	Wed, 26 Jan 2011 15:57:06 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Kees Cook <kees.cook@...onical.com>
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

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!

> use %pK for kernel
> addresses to reduce potential information leaks that might be used to
> help target kernel privilege escalation exploits.
> 
> 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.)
> 
> Note that when compiling with -Wformat, these harmless warnings will
> be emitted, and can be ignored:
>   warning: '0' flag used with ___%p___ gnu_printf format

OK, so what applications did this patch just break?
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