diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3f520cd837fb8..d41c091546b72 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4265,7 +4265,7 @@ 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)