Merge branch 'mptcp-pm-a-few-more-fixes'

Matthieu Baerts says:

====================
mptcp: pm: a few more fixes

Three small fixes related to the MPTCP path-manager:

- Patch 1: correctly reflect the backup flag to the corresponding local
  address entry of the userspace path-manager. A fix for v5.19.

- Patch 2: hold the PM lock when deleting an entry from the local
  addresses of the userspace path-manager to avoid messing up with this
  list. A fix for v5.19.

- Patch 3: use _rcu variant to iterate the in-kernel path-manager's
  local addresses list, when under rcu_read_lock(). A fix for v5.17.
====================

Link: https://patch.msgid.link/20241112-net-mptcp-misc-6-12-pm-v1-0-b835580cefa8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/mptcp/pm_netlink.c

@@ -524,7 +524,8 @@ __lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info)
 {
 	struct mptcp_pm_addr_entry *entry;
 
-	list_for_each_entry(entry, &pernet->local_addr_list, list) {
+	list_for_each_entry_rcu(entry, &pernet->local_addr_list, list,
+				lockdep_is_held(&pernet->lock)) {
 		if (mptcp_addresses_equal(&entry->addr, info, entry->addr.port))
 			return entry;
 	}

net/mptcp/pm_userspace.c

@@ -308,14 +308,17 @@ int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info)
 
 	lock_sock(sk);
 
+	spin_lock_bh(&msk->pm.lock);
 	match = mptcp_userspace_pm_lookup_addr_by_id(msk, id_val);
 	if (!match) {
 		GENL_SET_ERR_MSG(info, "address with specified id not found");
+		spin_unlock_bh(&msk->pm.lock);
 		release_sock(sk);
 		goto out;
 	}
 
 	list_move(&match->list, &free_list);
+	spin_unlock_bh(&msk->pm.lock);
 
 	mptcp_pm_remove_addrs(msk, &free_list);
 
@@ -560,6 +563,7 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	struct nlattr *token = info->attrs[MPTCP_PM_ATTR_TOKEN];
 	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
 	struct net *net = sock_net(skb->sk);
+	struct mptcp_pm_addr_entry *entry;
 	struct mptcp_sock *msk;
 	int ret = -EINVAL;
 	struct sock *sk;
@@ -601,6 +605,17 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	if (loc.flags & MPTCP_PM_ADDR_FLAG_BACKUP)
 		bkup = 1;
 
+	spin_lock_bh(&msk->pm.lock);
+	list_for_each_entry(entry, &msk->pm.userspace_pm_local_addr_list, list) {
+		if (mptcp_addresses_equal(&entry->addr, &loc.addr, false)) {
+			if (bkup)
+				entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+			else
+				entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+		}
+	}
+	spin_unlock_bh(&msk->pm.lock);
+
 	lock_sock(sk);
 	ret = mptcp_pm_nl_mp_prio_send_ack(msk, &loc.addr, &rem.addr, bkup);
 	release_sock(sk);