On Fri, Aug 12, 2022 at 09:47:06AM +0800, Yuan Yao wrote:
> Add checking to VMCS12's "VMCS shadowing", make sure the checking of
> VMCS12's vmcs_link_pointer for non-root mode VM{READ,WRITE} happens
> only if VMCS12's "VMCS shadowing" is 1.
>
> SDM says that for non-root mode the VMCS's "VMCS shadowing" must be 1
> (and the corresponding bits in VMREAD/VMWRITE bitmap must be 0) when
> condition checking of [B] is reached(please refer [A]), which means
> checking to VMCS link pointer for non-root mode VM{READ,WRITE} should
> happen only when "VMCS shadowing" = 1.
>
> Description from SDM Vol3(April 2022) Chapter 30.3 VMREAD/VMWRITE:
>
> IF (not in VMX operation)
> or (CR0.PE = 0)
> or (RFLAGS.VM = 1)
> or (IA32_EFER.LMA = 1 and CS.L = 0)
> THEN #UD;
> ELSIF in VMX non-root operation
> AND (“VMCS shadowing” is 0 OR
> source operand sets bits in range 63:15 OR
> VMREAD bit corresponding to bits 14:0 of source
> operand is 1) <------[A]
> THEN VMexit;
> ELSIF CPL > 0
> THEN #GP(0);
> ELSIF (in VMX root operation AND current-VMCS pointer is not valid) OR
> (in VMX non-root operation AND VMCS link pointer is not valid)
> THEN VMfailInvalid; <------ [B]
> ...
>
> Fixes: dd2d6042b7f4 ("kvm: nVMX: VMWRITE checks VMCS-link pointer before VMCS field")
> Signed-off-by: Yuan Yao <yuan.yao@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx/nested.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index ddd4367d4826..30685be54c5d 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5123,6 +5123,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
> */
> if (vmx->nested.current_vmptr == INVALID_GPA ||
> (is_guest_mode(vcpu) &&
> + nested_cpu_has_shadow_vmcs(vcpu) &&
Oops, should be "nested_cpu_has_shadow_vmcs(get_vmcs12(vcpu))".
> get_vmcs12(vcpu)->vmcs_link_pointer == INVALID_GPA))
> return nested_vmx_failInvalid(vcpu);
>
> @@ -5233,6 +5234,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
> */
> if (vmx->nested.current_vmptr == INVALID_GPA ||
> (is_guest_mode(vcpu) &&
> + nested_cpu_has_shadow_vmcs(vcpu) &&
Ditto.
> get_vmcs12(vcpu)->vmcs_link_pointer == INVALID_GPA))
> return nested_vmx_failInvalid(vcpu);
>
> --
> 2.27.0
>
