diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e0551c948c5945502c0a2a8cbef19cdf9fa3d4da..fac1d4eaa426868882e8082bc840b3861d33a7cf 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3890,7 +3890,7 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 	const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
 				    | KVM_S390_MEMOP_F_CHECK_ONLY;
 
-	if (mop->flags & ~supported_flags)
+	if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
 		return -EINVAL;
 
 	if (mop->size > MEM_OP_MAX_SIZE)