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

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Message-ID: <4DE53C80.3070406@zytor.com>
Date:	Tue, 31 May 2011 12:07:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dan Rosenberg <drosenberg@...curity.com>
CC:	Matthew Garrett <mjg@...hat.com>, Tony Luck <tony.luck@...il.com>,
	linux-kernel@...r.kernel.org, kees.cook@...onical.com,
	davej@...hat.com, torvalds@...ux-foundation.org,
	adobriyan@...il.com, eranian@...gle.com, penberg@...nel.org,
	davem@...emloft.net, Arjan van de Ven <arjan@...radead.org>,
	Valdis.Kletnieks@...edu, Andrew Morton <akpm@...ux-foundation.org>,
	pageexec@...email.hu, Ingo Molnar <mingo@...e.hu>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

On 05/31/2011 12:03 PM, Dan Rosenberg wrote:
> 
> Just for the record, I've put this patch on hold until there's some more
> consensus about whether boot-time randomization of the physical kernel
> address is the best approach.  There are some other potential issues
> that haven't been brought up yet publicly, such as the possibility of
> local attackers performing cache timing attacks to find the kernel image
> location at runtime, which may make traditional ASLR somewhat pointless
> regardless (except in the case of remote attackers, I suppose).  Perhaps
> HPA's suggestion of further modularizing the kernel would have some
> advantages in this regard.
> 

I'm probably going to implement the whole-image randomization as an
option in the Syslinux bootloader; it is a *lot* easier to do this
correctly in the bootloader.

	-hpa
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