If no subflow is attached to the 'subflow' endpoint that is being
removed, the addr ID will not be marked as available again.

Mark the linked ID as available when removing the 'subflow' endpoint if
no subflow is attached to it.

While at it, the local_addr_used counter is decremented if the ID was
marked as being used to reflect the reality, but also to allow adding
new endpoints after that.

Fixes: b6c08380860b ("mptcp: remove addr and subflow in PM netlink")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index d44d318dce03..36a1bda25d2e 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1454,8 +1454,16 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
 		remove_subflow = lookup_subflow_by_saddr(&msk->conn_list, addr);
 		mptcp_pm_remove_anno_addr(msk, addr, remove_subflow &&
 					  !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
-		if (remove_subflow)
+		if (remove_subflow) {
 			mptcp_pm_remove_subflow(msk, &list);
+		} else if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
+			/* If the subflow has been used, but now closed */
+			spin_lock_bh(&msk->pm.lock);
+			if (!__test_and_set_bit(entry->addr.id, msk->pm.id_avail_bitmap))
+				msk->pm.local_addr_used--;
+			spin_unlock_bh(&msk->pm.lock);
+		}
+
 		release_sock(sk);
 
 next:

-- 
2.45.2