net: hso: fix muxed tty registration

commit e8f69b1 upstream.

If resource allocation and registration fail for a muxed tty device
(e.g. if there are no more minor numbers) the driver should not try to
deregister the never-registered (or already-deregistered) tty.

Fix up the error handling to avoid dereferencing a NULL pointer when
attempting to remove the character device.

Fixes: 72dc1c0 ("HSO: add option hso driver")
Cc: stable@vger.kernel.org	# 2.6.27
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/usb/hso.c

@@ -2721,14 +2721,14 @@ struct hso_device *hso_create_mux_serial_device(struct usb_interface *interface,
 
 	serial = kzalloc(sizeof(*serial), GFP_KERNEL);
 	if (!serial)
-		goto exit;
+		goto err_free_dev;
 
 	hso_dev->port_data.dev_serial = serial;
 	serial->parent = hso_dev;
 
 	if (hso_serial_common_create
 	    (serial, 1, CTRL_URB_RX_SIZE, CTRL_URB_TX_SIZE))
-		goto exit;
+		goto err_free_serial;
 
 	serial->tx_data_length--;
 	serial->write_data = hso_mux_serial_write_data;
@@ -2744,11 +2744,9 @@ struct hso_device *hso_create_mux_serial_device(struct usb_interface *interface,
 	/* done, return it */
 	return hso_dev;
 
-exit:
-	if (serial) {
-		tty_unregister_device(tty_drv, serial->minor);
-		kfree(serial);
-	}
+err_free_serial:
+	kfree(serial);
+err_free_dev:
 	kfree(hso_dev);
 	return NULL;