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

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Date:	Fri, 4 Dec 2009 08:52:12 -0800
From:	"Cihula, Joseph" <joseph.cihula@...el.com>
To:	Pavel Machek <pavel@....cz>, "Wang, Shane" <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>,
	"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>,
	"Brown, Len" <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
Subject: RE: [PATCH] intel_txt: add s3 userspace memory integrity
	verification

> From: Pavel Machek [mailto:pavel@....cz]
> Sent: Friday, December 04, 2009 12:29 AM
>
> > 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.

I've responded to that in your previous email thread, so let's keep the technical discussion of what is MAC'ed to just that one thread.

> 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.

Really the only requirement is (as discussed in the previous thread) that it only use code and data within [_text, _end - _text]--do you think that this really needs to be called out?  do_suspend_lowlevel() is a very simple function that has just the one (resume path) call to another simple function--it doesn't seem likely that it would violate this.

>
> 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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