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Subject[PATCH 3/3] KVM: nVMX: check for invalid hdr.vmx.flags
Date
hdr.vmx.flags is meant for future extensions to the ABI, rejecting
invalid flags is necessary to avoid broken half-loads of the
nVMX state.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/vmx/nested.c | 3 +++
.../kvm/x86_64/vmx_set_nested_state_test.c | 13 +++++++++++++
2 files changed, 16 insertions(+)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 6a0e32a7418c..11e4df560018 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6079,6 +6079,9 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
~(KVM_STATE_NESTED_SMM_GUEST_MODE | KVM_STATE_NESTED_SMM_VMXON))
return -EINVAL;

+ if (kvm_state->hdr.vmx.flags & ~KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE)
+ return -EINVAL;
+
/*
* SMM temporarily disables VMX, so we cannot be in guest mode,
* nor can VMLAUNCH/VMRESUME be pending. Outside SMM, SMM flags
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 94f28a657569..d59f3eb67c8f 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
@@ -146,6 +146,11 @@ void test_vmx_nested_state(struct kvm_vm *vm)
state->hdr.vmx.smm.flags = 1;
test_nested_state_expect_einval(vm, state);

+ /* Invalid flags are rejected. */
+ set_default_vmx_state(state, state_sz);
+ state->hdr.vmx.flags = ~0;
+ test_nested_state_expect_einval(vm, state);
+
/* It is invalid to have vmxon_pa == -1ull and vmcs_pa != -1ull. */
set_default_vmx_state(state, state_sz);
state->hdr.vmx.vmxon_pa = -1ull;
@@ -206,6 +211,14 @@ void test_vmx_nested_state(struct kvm_vm *vm)
state->flags = 0;
test_nested_state(vm, state);

+ /* Invalid flags are rejected, even if no VMCS loaded. */
+ set_default_vmx_state(state, state_sz);
+ state->size = sizeof(*state);
+ state->flags = 0;
+ state->hdr.vmx.vmcs12_pa = -1;
+ state->hdr.vmx.flags = ~0;
+ test_nested_state_expect_einval(vm, state);
+
/* vmxon_pa cannot be the same address as vmcs_pa. */
set_default_vmx_state(state, state_sz);
state->hdr.vmx.vmxon_pa = 0;
--
2.26.2
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