[PATCH 5.4 151/152] kvm: nVMX: VMWRITE checks VMCS-link pointer before VMCS field

Greg Kroah-Hartman
2020-03-03T17:58:30Z

From: Jim Mattson <jmattson@google.com>

commit dd2d6042b7f4a5440705b4ffc6c4c2dba81a43b7 upstream.

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.

For consistency, modify both handle_vmwrite and handle_vmread, even
though there was no problem with the latter.

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>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Peter Shier <pshier@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Reviewed-by: Jon Cargille <jcargill@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/vmx/nested.c | 59 +++++++++++++++++++---------------------------
1 file changed, 25 insertions(+), 34 deletions(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4609,32 +4609,28 @@ static int handle_vmread(struct kvm_vcpu
{
unsigned long field;
u64 field_value;
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
int len;
gva_t gva = 0;
- struct vmcs12 *vmcs12;
+ struct vmcs12 *vmcs12 = is_guest_mode(vcpu) ? get_shadow_vmcs12(vcpu)
+ : get_vmcs12(vcpu);
struct x86_exception e;
short offset;

if (!nested_vmx_check_permission(vcpu))
return 1;

- if (to_vmx(vcpu)->nested.current_vmptr == -1ull)
+ /*
+ * In VMX non-root operation, when the VMCS-link pointer is -1ull,
+ * any VMREAD sets the ALU flags for VMfailInvalid.
+ */
+ if (vmx->nested.current_vmptr == -1ull ||
+ (is_guest_mode(vcpu) &&
+ get_vmcs12(vcpu)->vmcs_link_pointer == -1ull))
return nested_vmx_failInvalid(vcpu);

- if (!is_guest_mode(vcpu))
- vmcs12 = get_vmcs12(vcpu);
- else {
- /*
- * When vmcs->vmcs_link_pointer is -1ull, any VMREAD
- * 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);
- }
-
/* Decode instruction info and find the field to read */
field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));

@@ -4713,13 +4709,20 @@ static int handle_vmwrite(struct kvm_vcp
*/
u64 field_value = 0;
struct x86_exception e;
- struct vmcs12 *vmcs12;
+ struct vmcs12 *vmcs12 = is_guest_mode(vcpu) ? get_shadow_vmcs12(vcpu)
+ : get_vmcs12(vcpu);
short offset;

if (!nested_vmx_check_permission(vcpu))
return 1;

- if (vmx->nested.current_vmptr == -1ull)
+ /*
+ * In VMX non-root operation, when the VMCS-link pointer is -1ull,
+ * any VMWRITE sets the ALU flags for VMfailInvalid.
+ */
+ if (vmx->nested.current_vmptr == -1ull ||
+ (is_guest_mode(vcpu) &&
+ get_vmcs12(vcpu)->vmcs_link_pointer == -1ull))
return nested_vmx_failInvalid(vcpu);

if (vmx_instruction_info & (1u << 10))
@@ -4747,24 +4750,12 @@ static int handle_vmwrite(struct kvm_vcp
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);
- }
+ /*
+ * 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_guest_mode(vcpu) && !is_shadow_field_rw(field))
+ copy_vmcs02_to_vmcs12_rare(vcpu, vmcs12);

offset = vmcs_field_to_offset(field);
if (offset < 0)