As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - INFLIGHT FLIGHT ATTENDANTS AND PILOTS REPORTED HOT SMELL AND SMALL AMOUNT OF SMOKE IN MID CABIN. RETURNED TO ORD AND LANDED OVERWEIGHT WITHOUT INCIDENT. SMOKE CLEARED ON FINAL. ACCOMPLISHED OVERWEIGHT INSPECTION AND LEAK CHECK. AS PRECAUTION REPLACED BOTH PACK PRESSURE SHUT OFF VALVES AND EQUIPMENT COOLING FAN. SYSTEM GROUND CHECKED NORMAL OPERATION.