USB: fix double frees in error code paths of ipaq driver

the error code paths can be enter with buffers to freed buffers.
Serial core would do a kfree() on memory already freed.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ipaq.c

@@ -646,11 +646,13 @@ static int ipaq_open(struct usb_serial_port *port, struct file *filp)
 	kfree(port->bulk_out_buffer);
 	port->bulk_in_buffer = kmalloc(URBDATA_SIZE, GFP_KERNEL);
 	if (port->bulk_in_buffer == NULL) {
+		port->bulk_out_buffer = NULL; /* prevent double free */
 		goto enomem;
 	}
 	port->bulk_out_buffer = kmalloc(URBDATA_SIZE, GFP_KERNEL);
 	if (port->bulk_out_buffer == NULL) {
 		kfree(port->bulk_in_buffer);
+		port->bulk_in_buffer = NULL;
 		goto enomem;
 	}
 	port->read_urb->transfer_buffer = port->bulk_in_buffer;