USB: misc: cypress_cy7c63: check for short transfer

As we process the second byte of a control transfer, transfers
of less than 2 bytes must be discarded.

This bug is as old as the driver.

SIgned-off-by: Oliver Neukum <[e-mail]>
CC: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/cypress_cy7c63.c

···
 				 USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
 				 address, data, iobuf, CYPRESS_MAX_REQSIZE,
 				 USB_CTRL_GET_TIMEOUT);
+	/* we must not process garbage */
+	if (retval < 2)
+		goto err_buf;
 
 	/* store returned data (more READs to be added) */
 	switch (request) {
···
 			break;
 	}
 
+err_buf:
 	kfree(iobuf);
 error:
 	return retval;