tree ccb039dac1597c6cd228ae5aa92a67bd88accd39
parent 46fb160ebf1736bf65acf4d5cd6a12de06384337
author Maxim Levitsky <mlevitsk@redhat.com> 1695922431 +0300
committer Nandhini Rengaraj <nrengaraj@google.com> 1700267265 +0000

x86: KVM: SVM: always update the x2avic msr interception

commit b65235f6e102354ccafda601eaa1c5bef5284d21 upstream.

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

BUG=b/311157876
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2023-5090 in the linux kernel.

cos-patch: security-moderate
Fixes: 4d1d7942e36a ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode")
Cc: stable@vger.kernel.org
Change-Id: Ib29848fe5c13e21d3b851671d6abf451723a688a
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>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nandhini Rengaraj <nrengaraj@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/61334
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Anil Altinay <aaltinay@google.com>