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

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Message-ID: <4DE046D9.7050700@zytor.com>
Date:	Fri, 27 May 2011 17:50:33 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Olivier Galibert <galibert@...ox.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dan Rosenberg <drosenberg@...curity.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, 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,
	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

On 05/27/2011 02:51 PM, Olivier Galibert wrote:
> On Fri, May 27, 2011 at 08:17:24PM +0200, Ingo Molnar wrote:
>>  - A root exploit will still not give away the location of the
>>    kernel (assuming module loading has been disabled after bootup),
>>    so a rootkit cannot be installed 'silently' on the system, into
>>    RAM only, evading most offline-storage-checking tools.
>>
>>    With static linking this is not possible: reading the kernel image
>>    as root trivially exposes the kernel's location.
> 
> There's something I don't get there.  If you managed to escalate your
> priviledges enough that you have physical ram access, there's a
> billion things you can do to find the kernel, including vector
> tracing, pattern matching, looking at the page tables, etc.
> 
> What am I missing?
> 

Just makes it harder to automate an attack, and more likely that it will
fail.  It's an arms race, of course.

	-hpa
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