[Lguest] [PATCH] Fix Malicious Guest GDT Host Crash

[Rusty Russell]

On Wed, 2007-08-08 at 21:40 -0700, ron minnich wrote:
> On 8/7/07, Rusty Russell <rusty at rustcorp.com.au> wrote:
> > Hi all,
> >
> >         Testing would be appreciated (esp. Ron?): I'd like to push this as soon
> > as possible into 2.6.23.  I thought of it while pondering kvm-lite, and
> > then proved it was a problem...
> 
> Works fine here.
> 
> Be aware that in the early Plan 9 port to lguest I created a gdt entry
> and forgot to wrap the GDT #  with a macro with the result that I
> loaded a gdt # instead of a selector into the gdt entry, and when the
> guest switched back to the host (and back to guest, I guess) it
> crashed my machine so hard that it went into the BIOS 'let's set this
> brand new thinkpad up' dialog.

Wow.  That's impressive.  It's understandable, however: I got a host
triplefault here when a malformed GDT entry caused a #GP on guest entry.

I'd be interested to check that this fixes it, but I'm pretty confident
(it fixed it here).

> The guys at the Plan 9  BOF at Google thought lguest was pretty darn cool.

Cool!

Rusty.