USB: serial: add endpoint sanity check to core

Allow drivers to specify a minimum number of endpoints per type, which
USB serial core will verify after subdriver probe has returned (where
the current alternate setting may have been changed).

Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/usb-serial.c

@@ -848,21 +848,26 @@ static int usb_serial_probe(struct usb_interface *interface,
 		if (epds->num_bulk_in == 0 || epds->num_bulk_out == 0) {
 			dev_info(ddev, "PL-2303 hack: descriptors matched but endpoints did not\n");
 			retval = -ENODEV;
-			kfree(epds);
-			goto err_put_serial;
+			goto err_free_epds;
 		}
 	}
 	/* END HORRIBLE HACK FOR PL2303 */
 #endif
-
+	if (epds->num_bulk_in < type->num_bulk_in ||
+			epds->num_bulk_out < type->num_bulk_out ||
+			epds->num_interrupt_in < type->num_interrupt_in ||
+			epds->num_interrupt_out < type->num_interrupt_out) {
+		dev_err(ddev, "required endpoints missing\n");
+		retval = -ENODEV;
+		goto err_free_epds;
+	}
 #ifdef CONFIG_USB_SERIAL_GENERIC
 	if (type == &usb_serial_generic_device) {
 		num_ports = epds->num_bulk_out;
 		if (num_ports == 0) {
 			dev_err(ddev, "Generic device with no bulk out, not allowed.\n");
 			retval = -EIO;
-			kfree(epds);
-			goto err_put_serial;
+			goto err_free_epds;
 		}
 		dev_info(ddev, "The \"generic\" usb-serial driver is only for testing and one-off prototypes.\n");
 		dev_info(ddev, "Tell linux-usb@vger.kernel.org to add your device to a proper driver.\n");
@@ -1085,6 +1090,8 @@ exit:
 
 probe_error:
 	retval = -EIO;
+err_free_epds:
+	kfree(epds);
 err_put_serial:
 	usb_serial_put(serial);
 err_put_module:

include/linux/usb/serial.h

@@ -188,6 +188,10 @@ static inline void usb_set_serial_data(struct usb_serial *serial, void *data)
  * @id_table: pointer to a list of usb_device_id structures that define all
  *	of the devices this structure can support.
  * @num_ports: the number of different ports this device will have.
+ * @num_bulk_in: minimum number of bulk-in endpoints
+ * @num_bulk_out: minimum number of bulk-out endpoints
+ * @num_interrupt_in: minimum number of interrupt-in endpoints
+ * @num_interrupt_out: minimum number of interrupt-out endpoints
  * @bulk_in_size: minimum number of bytes to allocate for bulk-in buffer
  *	(0 = end-point size)
  * @bulk_out_size: bytes to allocate for bulk-out buffer (0 = end-point size)
@@ -235,6 +239,11 @@ struct usb_serial_driver {
 
 	unsigned char		num_ports;
 
+	unsigned char		num_bulk_in;
+	unsigned char		num_bulk_out;
+	unsigned char		num_interrupt_in;
+	unsigned char		num_interrupt_out;
+
 	size_t			bulk_in_size;
 	size_t			bulk_out_size;