mptcp: make sure flag signal is set when add addr with port

When add address with port, it is mean to create a listening socket,
and send an ADD_ADDR to remote, so it must have flag signal set,
add this check in mptcp_pm_parse_addr().

Fixes: a77e9179 ("mptcp: deal with MPTCP_PM_ADDR_ATTR_PORT in PM netlink")
Acked-by: Geliang Tang <geliangtang@gmail.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -971,8 +971,14 @@ static int mptcp_pm_parse_addr(struct nlattr *attr, struct genl_info *info,
 	if (tb[MPTCP_PM_ADDR_ATTR_FLAGS])
 		entry->flags = nla_get_u32(tb[MPTCP_PM_ADDR_ATTR_FLAGS]);
 
-	if (tb[MPTCP_PM_ADDR_ATTR_PORT])
+	if (tb[MPTCP_PM_ADDR_ATTR_PORT]) {
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
+			NL_SET_ERR_MSG_ATTR(info->extack, attr,
+					    "flags must have signal when using port");
+			return -EINVAL;
+		}
 		entry->addr.port = htons(nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_PORT]));
+	}
 
 	return 0;
 }