1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 5ff3485acb60..01bd7b7a6866 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1116,6 +1116,11 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
                 break;
         case HVCALL_POST_MESSAGE:
         case HVCALL_SIGNAL_EVENT:
+                /* don't bother userspace if it has no way to handle it */
+                if (!vcpu_to_synic(vcpu)->active) {
+                        res = HV_STATUS_INVALID_HYPERCALL_CODE;
+                        break;
+                }
                 vcpu->run->exit_reason = KVM_EXIT_HYPERV;
                 vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
                 vcpu->run->hyperv.u.hcall.input = param;