Bluetooth: hci_{ldisc,serdev}: check percpu_init_rwsem() failure

syzbot is reporting NULL pointer dereference at hci_uart_tty_close() [1],
for rcu_sync_enter() is called without rcu_sync_init() due to
hci_uart_tty_open() ignoring percpu_init_rwsem() failure.

While we are at it, fix that hci_uart_register_device() ignores
percpu_init_rwsem() failure and hci_uart_unregister_device() does not
call percpu_free_rwsem().

Link: https://syzkaller.appspot.com/bug?extid=576dfca25381fb6fbc5f [1]
Reported-by: syzbot <[e-mail]>
Signed-off-by: Tetsuo Handa <[e-mail]>
Fixes: 67d2f8781b9f00d1 ("Bluetooth: hci_ldisc: Allow sleeping while proto locks are held.")
Fixes: d73e172816652772 ("Bluetooth: hci_serdev: Init hci_uart proto_lock to avoid oops")
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

drivers/bluetooth/hci_ldisc.c

···
 		BT_ERR("Can't allocate control structure");
 		return -ENFILE;
 	}
+	if (percpu_init_rwsem(&hu->proto_lock)) {
+		BT_ERR("Can't allocate semaphore structure");
+		kfree(hu);
+		return -ENOMEM;
+	}
 
 	tty->disc_data = hu;
 	hu->tty = tty;
···
 
 	INIT_WORK(&hu->init_ready, hci_uart_init_work);
 	INIT_WORK(&hu->write_work, hci_uart_write_work);
-
-	percpu_init_rwsem(&hu->proto_lock);
 
 	/* Flush any pending characters in the driver */
 	tty_driver_flush_buffer(tty);

drivers/bluetooth/hci_serdev.c

···
 
 	serdev_device_set_client_ops(hu->serdev, &hci_serdev_client_ops);
 
+	if (percpu_init_rwsem(&hu->proto_lock))
+		return -ENOMEM;
+
 	err = serdev_device_open(hu->serdev);
 	if (err)
-		return err;
-
-	percpu_init_rwsem(&hu->proto_lock);
+		goto err_rwsem;
 
 	err = p->open(hu);
 	if (err)
···
 	p->close(hu);
 err_open:
 	serdev_device_close(hu->serdev);
+err_rwsem:
+	percpu_free_rwsem(&hu->proto_lock);
 	return err;
 }
 EXPORT_SYMBOL_GPL(hci_uart_register_device);
···
 		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
 		serdev_device_close(hu->serdev);
 	}
+	percpu_free_rwsem(&hu->proto_lock);
 }
 EXPORT_SYMBOL_GPL(hci_uart_unregister_device);