linux-kernel - Re: [PATCH v6 0/7] Kernel base address randomization

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Date:	Tue, 01 Oct 2013 22:30:58 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	x86@...nel.org, kernel-hardening@...ts.openwall.com,
	adurbin@...gle.com, Eric Northup <digitaleric@...gle.com>,
	jln@...gle.com, wad@...gle.com,
	Mathias Krause <minipli@...glemail.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v6 0/7] Kernel base address randomization

On 10/01/2013 10:25 PM, Ingo Molnar wrote:
> 
> I mean, for example in an oops message we print data in words: the RIP, 
> other registers and stack contents. If any of these values lies within the 
> randomization range then we could de-randomize it.
> 
> So instead of exposing randomized values, we could expose de-randomized 
> values.
> 
> ( This isn't fool-proof: if some data value happens to lie within the 
>   random range spuriously then we'll incorrectly transform it. In the 
>   context of oops messages this should not be a big practical problem 
>   though. )
> 

I don't agree that this isn't a big practical problem.  I often find it
necessary to pick out "things that look like pointers".  Overall,
derandomization would make it possible to get really confused when you
have things like half a pointer overwritten.

	-hpa


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