RE: [PATCH] intel_txt: add s3 userspace memory integrityverification

[Cihula, Joseph]

> From: Pavel Machek [mailto:pavel@xxxxxx]
> 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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