audit: use struct_size() helper in audit_[send|make]_reply()

Make use of struct_size() helper instead of an open-coded calculation.

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

kernel/audit.c

@@ -1459,7 +1459,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 			security_release_secctx(ctx, len);
 		}
 		audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO, 0, 0,
-				 sig_data, sizeof(*sig_data) + len);
+				 sig_data, struct_size(sig_data, ctx, len));
 		kfree(sig_data);
 		break;
 	case AUDIT_TTY_GET: {

kernel/auditfilter.c

@@ -1092,7 +1092,7 @@ static void audit_list_rules(int seq, struct sk_buff_head *q)
 				break;
 			skb = audit_make_reply(seq, AUDIT_LIST_RULES, 0, 1,
 					       data,
-					       sizeof(*data) + data->buflen);
+					       struct_size(data, buf, data->buflen));
 			if (skb)
 				skb_queue_tail(q, skb);
 			kfree(data);