diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c2c26c2aad64..e056ad86ccd2 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2374,7 +2374,7 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
 
 	supported_flags = KVM_S390_MEMOP_F_SKEY_PROTECTION
 			  | KVM_S390_MEMOP_F_CHECK_ONLY;
-	if (mop->flags & ~supported_flags)
+	if (mop->flags & ~supported_flags || !mop->size)
 		return -EINVAL;
 	if (mop->size > MEM_OP_MAX_SIZE)
 		return -E2BIG;