usb gadget: composite: prevent OOPS for non-standard control request

The composite gadget will OOPS if the host sends a control request
targetted to an interface of an un-configured composite device. This patch
prevents this.

The OOPS was observed during WHQL USB CV tests. With this patch, the device
STALLs as per requirement.

Failing test case: From host do the following. I used libusb-1.0

1) Set configuration to zero.
	libusb_control_transfer(device_handle,
		0, /* standard OUT */
		0x9, /* setConfiguration */
		0, 0, NULL, 0, 0);

2) Query current configuratioan.
	libusb_control_transfer(device_handle,
		0x80, /* standard IN*/
		0x8, /* getConfiguration */
		0, 0, data, 1, 0);

3) Send the non-standard ctrl transfer targetted to interface
	libusb_control_transfer(device_handle,
		0x81, /* standard IN to interface*/
		0x6, /* getDescriptor */
		0x2300, 0, data, 0x12, 0);
Signed-off-by: Roger Quadros <roger.quadros@nokia.com>
Cc: stable <stable@kernel.org>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Michal Nazarewicz <m.nazarewicz@samsung.com>
Cc: Robert Lukassen <robert.lukassen@tomtom.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/composite.c

@@ -928,6 +928,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 		 */
 		switch (ctrl->bRequestType & USB_RECIP_MASK) {
 		case USB_RECIP_INTERFACE:
+			if (cdev->config)
 				f = cdev->config->interface[intf];
 			break;