USB: gadget: validate interface OS descriptor requests

Stall the control endpoint in case provided index exceeds array size of
MAX_CONFIG_INTERFACES or when the retrieved function pointer is null.

Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/composite.c

@@ -1988,6 +1988,9 @@ unknown:
 				if (w_index != 0x5 || (w_value >> 8))
 					break;
 				interface = w_value & 0xFF;
+				if (interface >= MAX_CONFIG_INTERFACES ||
+				    !os_desc_cfg->interface[interface])
+					break;
 				buf[6] = w_index;
 				count = count_ext_prop(os_desc_cfg,
 					interface);