libusb: Fix null pointer dereference in hid_open()

Make sure hid_device_info.serial_number is not null before passing it to
wcscmp().

When libusb can't open a device for any reason (e.g. file system
permissions), hid_device_info.serial_number is NULL. Make sure
hid_device_info.serial_number is not null before passing it to wcscmp(3).

Signed-off-by: Michael Hanselmann <[email protected]>

Author: hansmi

libusb/hid.c

@@ -619,7 +619,8 @@ hid_device * hid_open(unsigned short vendor_id, unsigned short product_id, const
 		if (cur_dev->vendor_id == vendor_id &&
 		    cur_dev->product_id == product_id) {
 			if (serial_number) {
-				if (wcscmp(serial_number, cur_dev->serial_number) == 0) {
+				if (cur_dev->serial_number &&
+				    wcscmp(serial_number, cur_dev->serial_number) == 0) {
 					path_to_open = cur_dev->path;
 					break;
 				}