linux-kernel - Re: [PATCH 5.5 111/176] KVM: nVMX: Emulate MTF when performing instruction emulation

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Date:   Wed, 4 Mar 2020 09:51:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Oliver Upton <oupton@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH 5.5 111/176] KVM: nVMX: Emulate MTF when performing
 instruction emulation

On Wed, Mar 04, 2020 at 09:43:18AM +0100, Paolo Bonzini wrote:
> On 04/03/20 09:26, Greg Kroah-Hartman wrote:
> > On Wed, Mar 04, 2020 at 09:19:09AM +0100, Paolo Bonzini wrote:
> >> On 04/03/20 09:10, Greg Kroah-Hartman wrote:
> >>> I'll be glad to just put KVM into the "never apply any patches to
> >>> stable unless you explicitly mark it as such", but the sad fact is that
> >>> many recent KVM fixes for reported CVEs never had any "Cc: stable@...r"
> >>> markings.
> >>
> >> Hmm, I did miss it in 433f4ba1904100da65a311033f17a9bf586b287e and
> >> acff78477b9b4f26ecdf65733a4ed77fe837e9dc, but that's going back to
> >> August 2018, so I can do better but it's not too shabby a record. :)
> > 
> > 35a571346a94 ("KVM: nVMX: Check IO instruction VM-exit conditions")
> > e71237d3ff1a ("KVM: nVMX: Refactor IO bitmap checks into helper function")
> > 
> > Were both from a few weeks ago and needed to resolve CVE-2020-2732 :(
> 
> No, they weren't, only the patch that was CCed stable was needed to
> resolve the CVE.

Ah, that's not what was posted to oss-security :(

> Remember that at this point a lot of bugfixes or vulnerabilities in KVM
> exploit corner cases of the architecture and don't show up with the
> usual guests (Linux, Windows, BSDs).  Since we didn't have full
> information on the impact on guests that people do run, we started with
> the bare minimum (the two patches above) but only for 5.6.  The idea was
> to collect follow-up patches for 2-4 weeks, decide which subset was
> stable-worthy, and only then post them as stable backport subsets.

Ok, that's fine, but it would be good if someone told me about this so
that I knew what was going on when people asked me about this type of
thing :)

thanks,

greg k-h