Re: [FYI PATCH 0/7] Mitigation for CVE-2018-12207

[Jan Kiszka]

On 18.11.19 14:58, Ralf Ramsauer wrote:
> Hi Dave,
>
> On 11/14/19 9:09 AM, Jan Kiszka wrote:
> > On 13.11.19 22:24, Dave Hansen wrote:
> > > On 11/13/19 12:23 AM, Paolo Bonzini wrote:
> > > > On 13/11/19 07:38, Jan Kiszka wrote:
> > > > > When reading MCE, error code 0150h, ie. SRAR, I was wondering if that
> > > > > couldn't simply be handled by the host. But I suppose the symptom of
> > > > > that erratum is not "just" regular recoverable MCE, rather
> > > > > sometimes/always an unrecoverable CPU state, despite the error code,
> > > > > right?
> > > > The erratum documentation talks explicitly about hanging the system, but
> > > > it's not clear if it's just a result of the OS mishandling the MCE, or
> > > > something worse. So I don't know. :( Pawan, do you?
> > >
> > > It's "something worse".
> > >
> > > I built a kernel module reproducer for this a long time ago. The
> > > symptom I observed was the whole system hanging hard, requiring me to go
> > > hit the power button. The MCE software machinery was not involved at
> > > all from what I could tell.
> >
> > Thanks for clarifying this - too bad.
> >
> > > About creating a unit test, I'd be personally happy to share my
> > > reproducer, but I built it before this issue was root-caused. There are
>
> I'd appreciate if you could share your code.
>
> > > actually quite a few underlying variants and a good unit test would make
> > > sure to exercise all of them. My reproducer probably only exercised a
> > > single case.
>
> Still, it triggers the issue, that's enough to compare it to my reproducer.
>
> > >
> >
> > Would be interesting to see this. Ralf and tried something quickly, but
> > there seems to be a detail missing or wrong.
>
> Yep, we still can't reproduce the issue on an affected CPU, and don't
> know what we miss.

I just realized that this thread stranded. Ralf told me that he got no 
access to that reproducer which would be very valuable for us right now 
to validate a static mitigation method in Jailhouse. Any chance to get 
the access?

Thanks a lot,
Jan

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