Jim Mattson <jmattson@xxxxxxxxxx> writes:
> 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@xxxxxxxxxx>
> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
> ---
> 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);
But (unless I'm missing some pre-requisite patch) we haven't set 'field'
yet, it happens later when we do
field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
> + } 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,
--
Vitaly
