A missing VMCS12 was not causing -EINVAL (it was just read with
copy_from_user, so it is not a security issue, but it is still
wrong). Test for VMCS12 validity and reject the nested state
if a VMCS12 is required but not present.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 13 ++++++++++---
arch/x86/kvm/vmx/nested.h | 5 +++++
.../kvm/x86_64/vmx_set_nested_state_test.c | 12 +++++++++++-
3 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index d4a4cec034d0..6a0e32a7418c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6108,9 +6108,16 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
if (ret)
return ret;
- /* Empty 'VMXON' state is permitted */
- if (kvm_state->size < sizeof(*kvm_state) + sizeof(*vmcs12))
- return 0;
+ /* Empty VMX data is permitted if no VMCS loaded */
+ if (kvm_state->size < sizeof(*kvm_state) + sizeof(*vmcs12)) {
+ /* See vmx_has_valid_vmcs12. */
+ if ((kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE) ||
+ (kvm_state->flags & KVM_STATE_NESTED_EVMCS) ||
+ (kvm_state->hdr.vmx.vmcs12_pa != -1ull))
+ return -EINVAL;
+ else
+ return 0;
+ }
if (kvm_state->hdr.vmx.vmcs12_pa != -1ull) {
if (kvm_state->hdr.vmx.vmcs12_pa == kvm_state->hdr.vmx.vmxon_pa ||
diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index 758bccc26cf9..197148d76b8f 100644
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -47,6 +47,11 @@ static inline struct vmcs12 *get_shadow_vmcs12(struct kvm_vcpu *vcpu)
return to_vmx(vcpu)->nested.cached_shadow_vmcs12;
}
+/*
+ * Note: the same condition is checked against the state provided by userspace
+ * in vmx_set_nested_state; if it is satisfied, the nested state must include
+ * the VMCS12.
+ */
static inline int vmx_has_valid_vmcs12(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
diff --git a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
index d14a34f1b018..94f28a657569 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
@@ -183,9 +183,19 @@ void test_vmx_nested_state(struct kvm_vm *vm)
state->hdr.vmx.smm.flags = KVM_STATE_NESTED_SMM_GUEST_MODE;
test_nested_state_expect_einval(vm, state);
- /* Size must be large enough to fit kvm_nested_state and vmcs12. */
+ /*
+ * Size must be large enough to fit kvm_nested_state and vmcs12
+ * if VMCS12 physical address is set
+ */
+ set_default_vmx_state(state, state_sz);
+ state->size = sizeof(*state);
+ state->flags = 0;
+ test_nested_state_expect_einval(vm, state);
+
set_default_vmx_state(state, state_sz);
state->size = sizeof(*state);
+ state->flags = 0;
+ state->hdr.vmx.vmcs12_pa = -1;
test_nested_state(vm, state);
/*
--
2.26.2
