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Date:   Mon, 6 Nov 2023 12:31:08 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     SeongJae Park <sj@kernel.org>
Cc:     stable@vger.kernel.org, Maxim Levitsky <mlevitsk@redhat.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 6.1.y] x86: KVM: SVM: always update the x2avic msr
 interception
Message-ID: <2023110600-tightwad-campfire-6a66@gregkh>
References: <2023102017-human-marine-7125@gregkh>
 <20231102175815.128993-1-sj@kernel.org>
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On Thu, Nov 02, 2023 at 05:58:15PM +0000, SeongJae Park wrote:
> From: Maxim Levitsky <mlevitsk@redhat.com>
> 
> The following problem exists since x2avic was enabled in the KVM:
> 
> svm_set_x2apic_msr_interception is called to enable the interception of
> the x2apic msrs.
> 
> In particular it is called at the moment the guest resets its apic.
> 
> Assuming that the guest's apic was in x2apic mode, the reset will bring
> it back to the xapic mode.
> 
> The svm_set_x2apic_msr_interception however has an erroneous check for
> '!apic_x2apic_mode()' which prevents it from doing anything in this case.
> 
> As a result of this, all x2apic msrs are left unintercepted, and that
> exposes the bare metal x2apic (if enabled) to the guest.
> Oops.
> 
> Remove the erroneous '!apic_x2apic_mode()' check to fix that.
> 
> This fixes CVE-2023-5090
> 
> Fixes: 4d1d7942e36a ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode")
> Cc: stable@vger.kernel.org
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> Message-Id: <20230928173354.217464-2-mlevitsk@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> (cherry picked from commit b65235f6e102354ccafda601eaa1c5bef5284d21)
> Signed-off-by: SeongJae Park <sj@kernel.org>

Now queued up, thanks.

greg k-h