From: Sean Christopherson <seanjc@google.com>
To: Aaron Lewis <aaronlewis@google.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com
Subject: Re: [PATCH v4 1/5] KVM: x86: Disallow the use of KVM_MSR_FILTER_DEFAULT_ALLOW in the kernel
Date: Fri, 7 Oct 2022 21:57:59 +0000 [thread overview]
Message-ID: <Y0Cg5zPruZZPg9Ed@google.com> (raw)
In-Reply-To: <20220921151525.904162-2-aaronlewis@google.com>
On Wed, Sep 21, 2022, Aaron Lewis wrote:
> Protect the kernel from using the flag KVM_MSR_FILTER_DEFAULT_ALLOW.
> Its value is 0, and using it incorrectly could have unintended
> consequences. E.g. prevent someone in the kernel from writing something
> like this.
>
> if (filter.flags & KVM_MSR_FILTER_DEFAULT_ALLOW)
> <allow the MSR>
>
> and getting confused when it doesn't work.
>
> It would be more ideal to remove this flag altogether, but userspace
> may already be using it, so protecting the kernel is all that can
> reasonably be done at this point.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> ---
Reviewed-by: Sean Christopherson <seanjc@google.com>
> Google's VMM is already using this flag, so we *know* that dropping the
> flag entirely will break userspace. All we can do at this point is
> prevent the kernel from using it.
LOL, nice.
next prev parent reply other threads:[~2022-10-07 21:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 15:15 [PATCH v4 0/5] MSR filtering and MSR exiting flag clean up Aaron Lewis
2022-09-21 15:15 ` [PATCH v4 1/5] KVM: x86: Disallow the use of KVM_MSR_FILTER_DEFAULT_ALLOW in the kernel Aaron Lewis
2022-10-07 21:57 ` Sean Christopherson [this message]
2022-09-21 15:15 ` [PATCH v4 2/5] KVM: x86: Add a VALID_MASK for the MSR exit reason flags Aaron Lewis
2022-10-07 22:04 ` Sean Christopherson
2022-09-21 15:15 ` [PATCH v4 3/5] KVM: x86: Add a VALID_MASK for the flag in kvm_msr_filter Aaron Lewis
2022-09-21 15:15 ` [PATCH v4 4/5] KVM: x86: Add a VALID_MASK for the flags in kvm_msr_filter_range Aaron Lewis
2022-09-21 15:15 ` [PATCH v4 5/5] selftests: kvm/x86: Test the flags in MSR filtering and MSR exiting Aaron Lewis
2022-10-07 22:24 ` Sean Christopherson
2022-11-02 17:09 ` [PATCH v4 0/5] MSR filtering and MSR exiting flag clean up Paolo Bonzini
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