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

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Date:	Fri, 27 May 2011 18:11:19 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Dave Jones <davej@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Dan Rosenberg <drosenberg@...curity.com>,
	Tony Luck <tony.luck@...il.com>, linux-kernel@...r.kernel.org,
	kees.cook@...onical.com, davem@...emloft.net, eranian@...gle.com,
	torvalds@...ux-foundation.org, 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 Friday, May 27, 2011, Ingo Molnar wrote:
> 
> * Dave Jones <davej@...hat.com> wrote:
> 
> > On Thu, May 26, 2011 at 03:32:13PM -0700, H. Peter Anvin wrote:
> >  > On 05/26/2011 03:18 PM, Rafael J. Wysocki wrote:
> >  > > 
> >  > > Well, as far as I can tell, this feature is going to break hibernation on
> >  > > both x86_32 and x86_64 at the moment, unless you can guarantee that the
> >  > > randomized kernel location will be the same for both the boot and the target
> >  > > kernels.
> >  > > 
> >  > 
> >  > Obviously we can't and we don't.  I'm a bit surprised at that
> >  > constraint... how can that constraint not break things like kernels of
> >  > slightly different size?
> > 
> > In Fedora at least, we make sure the kernel you thaw from is the 
> > same one you booted by diddling with grub to force the right kernel 
> > to be booted.
> 
> Btw., the hibernation code should save a signature and make sure that 
> the two kernels match! It's really broken if the code allows blind 
> thawing ...

It uses signatures, but on x86_64 you actually can use a different kernel
for loading the image, with some limitations.

I'd like to add a mechanism for passing the jump address into the hibernated
kernel in the kernel image, but that part is still missing.

Thanks,
Rafael
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