From 639a033fd765ed473dfee27028df5ccbe1038a2e Mon Sep 17 00:00:00 2001
From: Maxim Levitsky <mlevitsk@redhat.com>
Date: Mon, 19 Jul 2021 16:05:00 +0300
Subject: [PATCH] KVM: nSVM: always intercept VMLOAD/VMSAVE when nested
(CVE-2021-3656)
commit c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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 7f3b55561ae82..61f4186442352 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -149,6 +149,9 @@ 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,
--
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