linux-kernel - [PATCH v3 03/11] KVM: nVMX: Release eVMCS when enlightened VMENTRY was disabled

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Message-Id: <20210526132026.270394-4-vkuznets@redhat.com>
Date:   Wed, 26 May 2021 15:20:18 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 03/11] KVM: nVMX: Release eVMCS when enlightened VMENTRY was disabled

In theory, L1 can try to disable enlightened VMENTRY in VP assist page and
try to issue VMLAUNCH/VMRESUME. While nested_vmx_handle_enlightened_vmptrld()
properly handles this as 'EVMPTRLD_DISABLED', previously mapped eVMCS
remains mapped and thus all evmptr_is_valid() checks will still pass and
nested_vmx_run() will proceed when it shouldn't.

Release eVMCS immediately when we detect that enlightened vmentry was
disabled by L1.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c662278e4793..ea2c52aad8f0 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1980,8 +1980,10 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld(
 	if (likely(!vmx->nested.enlightened_vmcs_enabled))
 		return EVMPTRLD_DISABLED;
 
-	if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa))
+	if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa)) {
+		nested_release_evmcs(vcpu);
 		return EVMPTRLD_DISABLED;
+	}
 
 	if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
 		vmx->nested.current_vmptr = -1ull;
-- 
2.31.1