diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index b4712bcc697d..6c052411123c 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -429,6 +429,8 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	u64 val;
 	int wa_level;
 
+	if (KVM_REG_SIZE(reg->id) != sizeof(val))
+		return -ENOENT;
 	if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;