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

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Message-ID: <20110526203108.GJ29496@redhat.com>
Date:	Thu, 26 May 2011 16:31:08 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Valdis.Kletnieks@...edu
Cc:	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, torvalds@...ux-foundation.org,
	adobriyan@...il.com, penberg@...nel.org, hpa@...or.com,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, pageexec@...email.hu
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

On Thu, May 26, 2011 at 04:16:05PM -0400, Valdis.Kletnieks@...edu wrote:
> On Thu, 26 May 2011 16:01:21 EDT, Vivek Goyal said:
> 
> > Also randomization of kernel load address at run time will probably have
> > some issues with crashkernel=X@Y address syntax. So far user knew what
> > address first kernel is booting from and user could speicy where to 
> > reserve memory. Now it might happen that user specified some memory
> > to reserve and kernel decided to occupy that space resulting in failed
> > memory reservation for crash kernel.
> 
> That is however fixable - the randomizer just needs to make sure it doesn't
> overlay the crashkernel= space, and the crashkernel needs to be started with a
> 'norandomize' parameter.

That can be done but at the same time if kernel does not find any suitable
range to boot from, it should override crashkernel=X@Y settings and fail
crash memory reservation.

I guess with randomize space thing a more suitable crash kernel command
line will be crashkernel=X where kernel decides the base address for
second kernel depending on availability.

> If your threat model includes attacks on the
> crashkernel that randomizing will help with, you got bigger problems. ;)
> 

:-) I think norandomize for kdump kernel should be just fine.

Thanks
Vivek
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