usb: gadget: composite: avoid access beyond array max length

One of the USB CV MSC tests issues Get Max LUN request with
invalid wIndex (wIndex = 65535) parameter.

Add proper handling to prevent array index out of bounds issue.

Signed-off-by: Maulik Mankad <maulik@ti.com>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/composite.c

@@ -928,8 +928,9 @@ unknown:
 		 */
 		switch (ctrl->bRequestType & USB_RECIP_MASK) {
 		case USB_RECIP_INTERFACE:
-			if (cdev->config)
-				f = cdev->config->interface[intf];
+			if (!cdev->config || w_index >= MAX_CONFIG_INTERFACES)
+				break;
+			f = cdev->config->interface[intf];
 			break;
 
 		case USB_RECIP_ENDPOINT: