USB: serial: fix leak of usb serial module refrence count

The patch with title below makes reference count of usb serial module
always more than one after driver is bound.

	USB-BKL: Remove BKL use for usb serial driver probing

In fact, the patch above only replaces lock_kernel() with try_module_get()
, and does not use module_put() to do what unlock_kernel() did, so casue leak
of reference count of usb serial module and the module can not be unloaded
after serial driver is bound with device.

This patch fixes the issue, also simplifies such things:
	-only call try_module_get() once in the entry of usb_serial_probe()
	-only call module_put() once in the exit of usb_serial_probe

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: Johan Hovold <jhovold@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -736,6 +736,7 @@ int usb_serial_probe(struct usb_interface *interface,
 
 	serial = create_serial(dev, interface, type);
 	if (!serial) {
+		module_put(type->driver.owner);
 		dev_err(&interface->dev, "%s - out of memory\n", __func__);
 		return -ENOMEM;
 	}
@@ -746,11 +747,11 @@ int usb_serial_probe(struct usb_interface *interface,
 
 		id = get_iface_id(type, interface);
 		retval = type->probe(serial, id);
-		module_put(type->driver.owner);
 
 		if (retval) {
 			dbg("sub driver rejected device");
 			kfree(serial);
+			module_put(type->driver.owner);
 			return retval;
 		}
 	}
@@ -822,6 +823,7 @@ int usb_serial_probe(struct usb_interface *interface,
 		if (num_bulk_in == 0 || num_bulk_out == 0) {
 			dev_info(&interface->dev, "PL-2303 hack: descriptors matched but endpoints did not\n");
 			kfree(serial);
+			module_put(type->driver.owner);
 			return -ENODEV;
 		}
 	}
@@ -835,22 +837,15 @@ int usb_serial_probe(struct usb_interface *interface,
 			dev_err(&interface->dev,
 			    "Generic device with no bulk out, not allowed.\n");
 			kfree(serial);
+			module_put(type->driver.owner);
 			return -EIO;
 		}
 	}
 #endif
 	if (!num_ports) {
 		/* if this device type has a calc_num_ports function, call it */
-		if (type->calc_num_ports) {
-			if (!try_module_get(type->driver.owner)) {
-				dev_err(&interface->dev,
-					"module get failed, exiting\n");
-				kfree(serial);
-				return -EIO;
-			}
+		if (type->calc_num_ports)
 			num_ports = type->calc_num_ports(serial);
-			module_put(type->driver.owner);
-		}
 		if (!num_ports)
 			num_ports = type->num_ports;
 	}
@@ -1039,13 +1034,7 @@ int usb_serial_probe(struct usb_interface *interface,
 
 	/* if this device type has an attach function, call it */
 	if (type->attach) {
-		if (!try_module_get(type->driver.owner)) {
-			dev_err(&interface->dev,
-					"module get failed, exiting\n");
-			goto probe_error;
-		}
 		retval = type->attach(serial);
-		module_put(type->driver.owner);
 		if (retval < 0)
 			goto probe_error;
 		serial->attached = 1;
@@ -1088,10 +1077,12 @@ int usb_serial_probe(struct usb_interface *interface,
 exit:
 	/* success */
 	usb_set_intfdata(interface, serial);
+	module_put(type->driver.owner);
 	return 0;
 
 probe_error:
 	usb_serial_put(serial);
+	module_put(type->driver.owner);
 	return -EIO;
 }
 EXPORT_SYMBOL_GPL(usb_serial_probe);