mptcp: check userspace pm flags

Just like MPTCP_PM_ADDR_FLAG_SIGNAL flag is checked in userspace PM
announce mptcp_pm_nl_announce_doit(), PM flags should be checked in
mptcp_pm_nl_subflow_create_doit() too.

If MPTCP_PM_ADDR_FLAG_SUBFLOW flag is not set, there's no flags field
in the output of dump_addr. This looks a bit strange:

        id 10 flags  10.0.3.2

This patch uses mptcp_pm_parse_entry() instead of mptcp_pm_parse_addr()
to get the PM flags of the entry and check it. MPTCP_PM_ADDR_FLAG_SIGNAL
flag shouldn't be set here, and if MPTCP_PM_ADDR_FLAG_SUBFLOW flag is
missing from the netlink attribute, always set this flag.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm_userspace.c

@@ -334,7 +334,6 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info)
 	struct nlattr *laddr = info->attrs[MPTCP_PM_ATTR_ADDR];
 	struct mptcp_pm_addr_entry local = { 0 };
 	struct mptcp_addr_info addr_r;
-	struct mptcp_addr_info addr_l;
 	struct mptcp_sock *msk;
 	int err = -EINVAL;
 	struct sock *sk;
@@ -360,25 +359,31 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info)
 		goto create_err;
 	}
 
-	err = mptcp_pm_parse_addr(laddr, info, &addr_l);
+	err = mptcp_pm_parse_entry(laddr, info, true, &local);
 	if (err < 0) {
 		NL_SET_ERR_MSG_ATTR(info->extack, laddr, "error parsing local addr");
 		goto create_err;
 	}
 
+	if (local.flags & MPTCP_PM_ADDR_FLAG_SIGNAL) {
+		GENL_SET_ERR_MSG(info, "invalid addr flags");
+		err = -EINVAL;
+		goto create_err;
+	}
+	local.flags |= MPTCP_PM_ADDR_FLAG_SUBFLOW;
+
 	err = mptcp_pm_parse_addr(raddr, info, &addr_r);
 	if (err < 0) {
 		NL_SET_ERR_MSG_ATTR(info->extack, raddr, "error parsing remote addr");
 		goto create_err;
 	}
 
-	if (!mptcp_pm_addr_families_match(sk, &addr_l, &addr_r)) {
+	if (!mptcp_pm_addr_families_match(sk, &local.addr, &addr_r)) {
 		GENL_SET_ERR_MSG(info, "families mismatch");
 		err = -EINVAL;
 		goto create_err;
 	}
 
-	local.addr = addr_l;
 	err = mptcp_userspace_pm_append_new_local_addr(msk, &local, false);
 	if (err < 0) {
 		GENL_SET_ERR_MSG(info, "did not match address and id");
@@ -387,7 +392,7 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info)
 
 	lock_sock(sk);
 
-	err = __mptcp_subflow_connect(sk, &addr_l, &addr_r);
+	err = __mptcp_subflow_connect(sk, &local.addr, &addr_r);
 
 	release_sock(sk);