[PATCH] kvm: nVMX: VMWRITE checks VMCS-link pointer before VMCS field

[Jim Mattson <jmattson@google.com>]

According to the SDM, a VMWRITE in VMX non-root operation with an
invalid VMCS-link pointer results in VMfailInvalid before the validity
of the VMCS field in the secondary source operand is checked.

Fixes: 6d894f498f5d1 ("KVM: nVMX: vmread/vmwrite: Use shadow vmcs12 if running L2")
Signed-off-by: Jim Mattson <jmattson@google.com>
Cc: Liran Alon <liran.alon@oracle.com>
---
 arch/x86/kvm/vmx/nested.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 4aea7d304beb..146e1b40c69f 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4864,6 +4864,25 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 	if (vmx->nested.current_vmptr == -1ull)
 		return nested_vmx_failInvalid(vcpu);
 
+	if (!is_guest_mode(vcpu)) {
+		vmcs12 = get_vmcs12(vcpu);
+
+		/*
+		 * Ensure vmcs12 is up-to-date before any VMWRITE that dirties
+		 * vmcs12, else we may crush a field or consume a stale value.
+		 */
+		if (!is_shadow_field_rw(field))
+			copy_vmcs02_to_vmcs12_rare(vcpu, vmcs12);
+	} else {
+		/*
+		 * When vmcs->vmcs_link_pointer is -1ull, any VMWRITE
+		 * to shadowed-field sets the ALU flags for VMfailInvalid.
+		 */
+		if (get_vmcs12(vcpu)->vmcs_link_pointer == -1ull)
+			return nested_vmx_failInvalid(vcpu);
+		vmcs12 = get_shadow_vmcs12(vcpu);
+	}
+
 	if (vmx_instruction_info & (1u << 10))
 		field_value = kvm_register_readl(vcpu,
 			(((vmx_instruction_info) >> 3) & 0xf));
@@ -4889,25 +4908,6 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 		return nested_vmx_failValid(vcpu,
 			VMXERR_VMWRITE_READ_ONLY_VMCS_COMPONENT);
 
-	if (!is_guest_mode(vcpu)) {
-		vmcs12 = get_vmcs12(vcpu);
-
-		/*
-		 * Ensure vmcs12 is up-to-date before any VMWRITE that dirties
-		 * vmcs12, else we may crush a field or consume a stale value.
-		 */
-		if (!is_shadow_field_rw(field))
-			copy_vmcs02_to_vmcs12_rare(vcpu, vmcs12);
-	} else {
-		/*
-		 * When vmcs->vmcs_link_pointer is -1ull, any VMWRITE
-		 * to shadowed-field sets the ALU flags for VMfailInvalid.
-		 */
-		if (get_vmcs12(vcpu)->vmcs_link_pointer == -1ull)
-			return nested_vmx_failInvalid(vcpu);
-		vmcs12 = get_shadow_vmcs12(vcpu);
-	}
-
 	offset = vmcs_field_to_offset(field);
 	if (offset < 0)
 		return nested_vmx_failValid(vcpu,
-- 
2.24.0.393.g34dc348eaf-goog