linux-kernel - Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

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Date:	Thu, 04 Nov 2010 10:43:00 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Marcus Meissner <meissner@...e.de>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, jason.wessel@...driver.com,
	fweisbec@...il.com, mort@....com, akpm@...l.org,
	security@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of
 attacking

On 11/04/2010 10:38 AM, Tejun Heo wrote:
> Hello,
>
> On 11/04/2010 03:33 PM, Marcus Meissner wrote:
>> I mean the kernel could hide it from uname, but lsb_release,
>> /etc/redhat-release, /etc/SuSE-release etc still exist and then you
>> can still use the fixed address list table inside your exploit. But an
>> exploits needs to have such a list, making it harder to write.
>
> I do believe that making things more difficult to exploit helps.  Many
> people seem to think it only gives false sense of security tho.
>
>> I also briefly thought about kernel ASLR, but my knowledge of the kernel
>> loading is too limited whether this is even possible or at all useful.
>
> We already have relocatable kernel for kdump and IIRC it doesn't add
> runtime overhead, so putting the kernel at random address shouldn't be
> too difficult.  Not sure how useful that would be tho.
>

It's very coarse-grained relocation, which is why it works.

	-hpa

P.S. It's not just for kdump anymore.
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