drbd: fix NULL pointer deref in module init error path

If we want to iterate over the (as of yet still empty) list in the
cleanup path, we need to initialize the list before the first goto fail.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_main.c

@@ -2750,13 +2750,6 @@ int __init drbd_init(void)
 		return err;
 	}
 
-	err = drbd_genl_register();
-	if (err) {
-		printk(KERN_ERR "drbd: unable to register generic netlink family\n");
-		goto fail;
-	}
-
-
 	register_reboot_notifier(&drbd_notifier);
 
 	/*
@@ -2767,6 +2760,15 @@ int __init drbd_init(void)
 	drbd_proc = NULL; /* play safe for drbd_cleanup */
 	idr_init(&minors);
 
+	rwlock_init(&global_state_lock);
+	INIT_LIST_HEAD(&drbd_tconns);
+
+	err = drbd_genl_register();
+	if (err) {
+		printk(KERN_ERR "drbd: unable to register generic netlink family\n");
+		goto fail;
+	}
+
 	err = drbd_create_mempools();
 	if (err)
 		goto fail;
@@ -2778,9 +2780,6 @@ int __init drbd_init(void)
 		goto fail;
 	}
 
-	rwlock_init(&global_state_lock);
-	INIT_LIST_HEAD(&drbd_tconns);
-
 	retry.wq = create_singlethread_workqueue("drbd-reissue");
 	if (!retry.wq) {
 		printk(KERN_ERR "drbd: unable to create retry workqueue\n");