linux-kernel - Re: [PATCH] intel_txt: add s3 userspace memory integrity verification

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Message-ID: <20091204222524.GF32314@elf.ucw.cz>
Date:	Fri, 4 Dec 2009 23:25:24 +0100
From:	Pavel Machek <pavel@....cz>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"Cihula, Joseph" <joseph.cihula@...el.com>,
	"Wang, Shane" <shane.wang@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"chrisw@...s-sol.org" <chrisw@...s-sol.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"jbeulich@...ell.com" <jbeulich@...ell.com>,
	"peterm@...hat.com" <peterm@...hat.com>
Subject: Re: [PATCH] intel_txt: add s3 userspace memory integrity
 verification

On Fri 2009-12-04 09:53:37, H. Peter Anvin wrote:
> On 12/04/2009 09:13 AM, Andi Kleen wrote:
> >>>
> >>> So no, you did not audit do_suspend_lowlevel to make sure it does not
> >>> follow function pointers. Bad.
> >>
> >> We aren't aware of any code or data used by the resume path that is outside of the tboot-MAC'ed regions above--if you can point out any then we will gladly address them.
> > 
> > Code coverage is not enough, you need data coverage too.  If someone 
> > modifies kernel data it's typically easy to subvert code as a next step.
> > 
> 
> The only function pointers that are invoked on the do_suspend_lowlevel
> path are some paravirt_crap pointers, but those are located inside
> kernel static data.

What guarantees kernel static data are below 4GB? What prevents me
from booting with funny memmap where first 1MB is mapped, and then
memory above 4GB? What prevents Chinese company to ship machine with
such funny memmap?
									Pavel

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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