If there were any visa requirements/restrictions concerning the stop in RUH you would have been notified at time of booking similar to when booking HKG-JFK on CX888 you are advised of needing a transit visa for YVR.

It is likely that as the airport is designed as a transfer hub whether or not you are required to leave the aircraft or stay onboard, you will not require any documentation other than your boarding pass for AUH. Likely scenario due to short turnaround time is you will stay on aircraft.

Don't stress about it!