linux-kernel - Re: [PATCH 0/2] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <bf3af7eb-f4ce-b733-08d4-6ab7f106d6e6@amd.com>
Date:   Tue, 22 Aug 2023 08:55:20 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wu Zongyo <wuzongyo@...l.ustc.edu.cn>
Subject: Re: [PATCH 0/2] KVM: SVM: Fix unexpected #UD on INT3 in SEV guests

On 8/10/23 18:49, Sean Christopherson wrote:
> Fix a bug where KVM injects a bogus #UD for SEV guests when trying to skip
> an INT3 as part of re-injecting the associated #BP that got kinda sorta
> intercepted due to a #NPF occuring while vectoring/delivering the #BP.
> 
> I haven't actually confirmed that patch 1 fixes the bug, as it's a
> different change than what I originally proposed.  I'm 99% certain it will
> work, but I definitely need verification that it fixes the problem
> 
> Patch 2 is a tangentially related cleanup to make NRIPS a requirement for
> enabling SEV, e.g. so that we don't ever get "bug" reports of SEV guests
> not working when NRIPS is disabled.
> 
> Sean Christopherson (2):
>    KVM: SVM: Don't inject #UD if KVM attempts emulation of SEV guest w/o
>      insn
>    KVM: SVM: Require nrips support for SEV guests (and beyond)
> 
>   arch/x86/kvm/svm/sev.c |  2 +-
>   arch/x86/kvm/svm/svm.c | 37 ++++++++++++++++++++-----------------
>   arch/x86/kvm/svm/svm.h |  1 +
>   3 files changed, 22 insertions(+), 18 deletions(-)

We ran some stress tests against a version of the kernel without this fix 
and we're able to reproduce the issue, but not reliably, after a few 
hours. With this patch, it has not reproduced after running for a week.

Not as reliable a scenario as the original reporter, but this looks like 
it resolves the issue.

So, for the series:

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> 
> 
> base-commit: 240f736891887939571854bd6d734b6c9291f22e