As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT ATTENDANT REPORTED SMOKE IN CABIN FIFTEEN MINUTES AFTER TAKEOFF FROM UIO. SHORTLY AFTER, THE CREW RECEIVED AN EICAS MESSAGE FOR SMOKE IN LAV. THE AIRCRAFT WAS RETURNED TO UIO WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND TRIM AIR SHUTOFF VALVE STUCK. THE VALVE WAS PLACARDED INOPERATIVE. THE LAVATORIES WERE INSPECTED AND NO ABNORMALITIES WERE FOUND.