can: gw: Fix error path of cgw_module_init

This patch add error path for cgw_module_init to avoid possible crash if
some error occurs.

Fixes: c1aabdf3 ("can-gw: add netlink based CAN routing")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/gw.c

@@ -1046,32 +1046,50 @@ static __init int cgw_module_init(void)
 	pr_info("can: netlink gateway (rev " CAN_GW_VERSION ") max_hops=%d\n",
 		max_hops);
 
-	register_pernet_subsys(&cangw_pernet_ops);
+	ret = register_pernet_subsys(&cangw_pernet_ops);
+	if (ret)
+		return ret;
+
+	ret = -ENOMEM;
 	cgw_cache = kmem_cache_create("can_gw", sizeof(struct cgw_job),
 				      0, 0, NULL);
-
 	if (!cgw_cache)
-		return -ENOMEM;
+		goto out_cache_create;
 
 	/* set notifier */
 	notifier.notifier_call = cgw_notifier;
-	register_netdevice_notifier(&notifier);
+	ret = register_netdevice_notifier(&notifier);
+	if (ret)
+		goto out_register_notifier;
 
 	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_GETROUTE,
 				   NULL, cgw_dump_jobs, 0);
-	if (ret) {
-		unregister_netdevice_notifier(&notifier);
-		kmem_cache_destroy(cgw_cache);
-		return -ENOBUFS;
-	}
-
-	/* Only the first call to rtnl_register_module can fail */
-	rtnl_register_module(THIS_MODULE, PF_CAN, RTM_NEWROUTE,
-			     cgw_create_job, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_CAN, RTM_DELROUTE,
-			     cgw_remove_job, NULL, 0);
+	if (ret)
+		goto out_rtnl_register1;
+
+	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_NEWROUTE,
+				   cgw_create_job, NULL, 0);
+	if (ret)
+		goto out_rtnl_register2;
+	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_DELROUTE,
+				   cgw_remove_job, NULL, 0);
+	if (ret)
+		goto out_rtnl_register3;
 
 	return 0;
+
+out_rtnl_register3:
+	rtnl_unregister(PF_CAN, RTM_NEWROUTE);
+out_rtnl_register2:
+	rtnl_unregister(PF_CAN, RTM_GETROUTE);
+out_rtnl_register1:
+	unregister_netdevice_notifier(&notifier);
+out_register_notifier:
+	kmem_cache_destroy(cgw_cache);
+out_cache_create:
+	unregister_pernet_subsys(&cangw_pernet_ops);
+
+	return ret;
 }
 
 static __exit void cgw_module_exit(void)