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

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Message-ID: <20091204082927.GF1540@ucw.cz>
Date:	Fri, 4 Dec 2009 09:29:27 +0100
From:	Pavel Machek <pavel@....cz>
To:	Shane Wang <shane.wang@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"Cihula, Joseph" <joseph.cihula@...el.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>,
	"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>, len.brown@...el.com,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] intel_txt: add s3 userspace memory integrity
	verification



> This patch added verification for userspace memory integrity after
>  S3 resume.

It does not work.

> Integrity verification for other memory (say kernel itself) has been done by tboot.
>

Not true. Kernel  uses memory above 4G on x86-64. Including... say
console writing functions.

You can patch holes, but without description 'what does this protect
against' it is almost impossible to evaluate.


> +void tboot_do_suspend_lowlevel(void)
> +{
> +	int ret = -1;
> +
> +	if (!tboot_enabled()) {
> +		do_suspend_lowlevel();
> +		return;
> +	}
> +
> +	ret = tboot_pre_stack_switch();
> +	if (!ret) {
> +		tboot_switch_stack_call(tboot_do_suspend_lowlevel_call,
> +					(u64)new_stack_ptr);

...and here you add requirements to suspend_lowlevel that were not
there before. ("May not act on unchecksummed memory"), without
documenting them.

NAK.
									Pavel

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