Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH 5.10.y] KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) | Date | Mon, 16 Aug 2021 16:02:38 +0200 |
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From: Maxim Levitsky <mlevitsk@redhat.com>
[ upstream commit c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc ]
If L1 disables VMLOAD/VMSAVE intercepts, and doesn't enable Virtual VMLOAD/VMSAVE (currently not supported for the nested hypervisor), then VMLOAD/VMSAVE must operate on the L1 physical memory, which is only possible by making L0 intercept these instructions.
Failure to do so allowed the nested guest to run VMLOAD/VMSAVE unintercepted, and thus read/write portions of the host physical memory.
Fixes: 89c8a4984fc9 ("KVM: SVM: Enable Virtual VMLOAD VMSAVE feature")
Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- The above upstream SHA1 is still on its way to Linus
arch/x86/kvm/svm/nested.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 8a229db85302..df17146e841f 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -147,6 +147,9 @@ void recalc_intercepts(struct vcpu_svm *svm) for (i = 0; i < MAX_INTERCEPT; i++) c->intercepts[i] |= g->intercepts[i]; + + vmcb_set_intercept(c, INTERCEPT_VMLOAD); + vmcb_set_intercept(c, INTERCEPT_VMSAVE); } static void copy_vmcb_control_area(struct vmcb_control_area *dst, -- 2.26.3
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