Just like MPTCP_PM_ADDR_FLAG_SIGNAL flag is checked in userspace PM
announce mptcp_pm_nl_announce_doit(), MPTCP_PM_ADDR_FLAG_SUBFLOW flag
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 flags of the entry. Add MPTCP_PM_ADDR_FLAG_SUBFLOW flag check
in mptcp_pm_nl_subflow_create_doit().

Signed-off-by: Geliang Tang <geliang.tang@linux.dev>
---
 net/mptcp/pm_userspace.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index a7e3c0fcbbaa..cae425a67880 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -361,11 +361,18 @@ 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;
 	}
+	addr_l = local.addr;
+
+	if (!(local.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)) {
+		GENL_SET_ERR_MSG(info, "invalid addr flags");
+		err = -EINVAL;
+		goto create_err;
+	}
 
 	err = mptcp_pm_parse_addr(raddr, info, &addr_r);
 	if (err < 0) {
@@ -379,7 +386,6 @@ int mptcp_pm_nl_subflow_create_doit(struct sk_buff *skb, struct genl_info *info)
 		goto create_err;
 	}
 
-	local.addr = addr_l;
 	err = mptcp_userspace_pm_append_new_local_addr(msk, &local,
 						       mptcp_pm_parse_needs_id(laddr, info));
 	if (err < 0) {
-- 
2.40.1