The ID 0 is specific per MPTCP connections. The per netns entries cannot
have this special ID 0 then.

But that's different for the userspace PM where the entries are per
connection, they can then use this special ID 0.

Fixes: f40be0db0b76 ("mptcp: unify pm get_flags_and_ifindex_by_id")
Cc: stable@vger.kernel.org
Acked-by: Geliang Tang <geliang@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm.c         | 3 ---
 net/mptcp/pm_netlink.c | 4 ++++
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 925123e99889..3e6e0f5510bb 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -434,9 +434,6 @@ int mptcp_pm_get_flags_and_ifindex_by_id(struct mptcp_sock *msk, unsigned int id
 	*flags = 0;
 	*ifindex = 0;
 
-	if (!id)
-		return 0;
-
 	if (mptcp_pm_is_userspace(msk))
 		return mptcp_userspace_pm_get_flags_and_ifindex_by_id(msk, id, flags, ifindex);
 	return mptcp_pm_nl_get_flags_and_ifindex_by_id(msk, id, flags, ifindex);
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 28a9a3726146..d0a80f537fc3 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1395,6 +1395,10 @@ int mptcp_pm_nl_get_flags_and_ifindex_by_id(struct mptcp_sock *msk, unsigned int
 	struct sock *sk = (struct sock *)msk;
 	struct net *net = sock_net(sk);
 
+	/* No entries with ID 0 */
+	if (id == 0)
+		return 0;
+
 	rcu_read_lock();
 	entry = __lookup_addr_by_id(pm_nl_get_pernet(net), id);
 	if (entry) {

-- 
2.45.2