devlink: fix possible use-after-free and memory leaks in devlink_init()

The pernet operations structure for the subsystem must be registered
before registering the generic netlink family.

Make an unregister in case of unsuccessful registration.

Fixes: 687125b ("devlink: split out core code")
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
Link: https://lore.kernel.org/r/20240215203400.29976-1-kovalev@altlinux.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/devlink/core.c

@@ -529,14 +529,20 @@ static int __init devlink_init(void)
 {
 	int err;
 
-	err = genl_register_family(&devlink_nl_family);
-	if (err)
-		goto out;
 	err = register_pernet_subsys(&devlink_pernet_ops);
 	if (err)
 		goto out;
+	err = genl_register_family(&devlink_nl_family);
+	if (err)
+		goto out_unreg_pernet_subsys;
 	err = register_netdevice_notifier(&devlink_port_netdevice_nb);
+	if (!err)
+		return 0;
+
+	genl_unregister_family(&devlink_nl_family);
 
+out_unreg_pernet_subsys:
+	unregister_pernet_subsys(&devlink_pernet_ops);
 out:
 	WARN_ON(err);
 	return err;