[PATCH net v4] phonet: check register_netdevice_notifier() error in phonet_device_init()

[Minhong He]

phonet_device_init() registers a netdevice notifier before calling
phonet_netlink_register(), but does not check whether notifier
registration succeeded. On failure, netlink setup still proceeds and
init may return success without the notifier in place.

Also, the existing phonet_netlink_register() failure path called
phonet_device_exit(), which runs rtnl_unregister_all() even though
rtnl_register_many() already unwound any partial registration. Calling
the full exit helper on a partial init is not correct.

Check each registration error, including proc_create_net(), and unwind
only the steps that have succeeded so far, in reverse order.

Signed-off-by: Minhong He <heminhong@xxxxxxxxxx>
---
v4:
- Check proc_create_net() failure (-ENOMEM).
- Unwind in reverse registration order with one label per step
  (notifier -> proc -> pernet).
- Match phonet_device_exit() teardown order to the same sequence.
v3: https://lore.kernel.org/netdev/20260720070031.108248-1-heminhong@xxxxxxxxxx/
- Use goto-based unwind; do not call phonet_device_exit() on
  phonet_netlink_register() failure.
- Drop Fixes tag (theoretical init failure path).
v2: https://lore.kernel.org/netdev/20260716101504.158387-1-heminhong@xxxxxxxxxx/
v1: https://lore.kernel.org/netdev/20260713075212.431455-1-heminhong@xxxxxxxxxx/

 net/phonet/pn_dev.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index ad44831d6745..1272d49cd038 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -350,16 +350,34 @@ static struct pernet_operations phonet_net_ops = {
 /* Initialize Phonet devices list */
 int __init phonet_device_init(void)
 {
-	int err = register_pernet_subsys(&phonet_net_ops);
+	int err;
+
+	err = register_pernet_subsys(&phonet_net_ops);
 	if (err)
 		return err;
 
-	proc_create_net("pnresource", 0, init_net.proc_net, &pn_res_seq_ops,
-			sizeof(struct seq_net_private));
-	register_netdevice_notifier(&phonet_device_notifier);
+	if (!proc_create_net("pnresource", 0, init_net.proc_net,
+			     &pn_res_seq_ops, sizeof(struct seq_net_private))) {
+		err = -ENOMEM;
+		goto err_pernet;
+	}
+
+	err = register_netdevice_notifier(&phonet_device_notifier);
+	if (err)
+		goto err_proc;
+
 	err = phonet_netlink_register();
 	if (err)
-		phonet_device_exit();
+		goto err_notifier;
+
+	return 0;
+
+err_notifier:
+	unregister_netdevice_notifier(&phonet_device_notifier);
+err_proc:
+	remove_proc_entry("pnresource", init_net.proc_net);
+err_pernet:
+	unregister_pernet_subsys(&phonet_net_ops);
 	return err;
 }
 
@@ -367,8 +385,8 @@ void phonet_device_exit(void)
 {
 	rtnl_unregister_all(PF_PHONET);
 	unregister_netdevice_notifier(&phonet_device_notifier);
-	unregister_pernet_subsys(&phonet_net_ops);
 	remove_proc_entry("pnresource", init_net.proc_net);
+	unregister_pernet_subsys(&phonet_net_ops);
 }
 
 int phonet_route_add(struct net_device *dev, u8 daddr)
-- 
2.25.1