linux-kernel - Re: [RFC][PATCH] Randomize kernel base address on boot

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Date:	Fri, 27 May 2011 19:00:45 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Dan Rosenberg <drosenberg@...curity.com>,
	Tony Luck <tony.luck@...il.com>, linux-kernel@...r.kernel.org,
	davej@...hat.com, kees.cook@...onical.com, davem@...emloft.net,
	eranian@...gle.com, adobriyan@...il.com, penberg@...nel.org,
	hpa@...or.com, Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Valdis.Kletnieks@...edu, pageexec@...email.hu
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> If you compile your own kernel version, you're already home free, 
> and load-time randomization is pointless.

Most successful exploits work in two steps: first a local exploit 
(weak password with a user, stupid script escaping bug, or a buffer 
overflow somewhere), then a local kernel exploit to gain root and 
kernel access. (for a rootkit and what not)

Straight remote root exploits are pretty rare - and per system 
relinking only protects against that.

The problem with your relinking solution is that a local attacker can 
easily figure out where the kernel is. So this does not protect 
against the more common break-in scenario.

Kernel image randomization makes this last step really 
indeterministic and thus dangerous to attackers.

Thanks,

	Ingo
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