The "official" NFL record for career sacks in the Super Bowl is 4.5 (held by Charles Haley* in five Games.) The single game record is 3.0 set by Reggie White against Drew Bledsoe and new England in SB XXXI.
Greenwood sacked Roger Staubach four times in SB X and once in SB XIII. But he is not in the record book because sacks were not an official record in the seventies.
*Haley also belongs in the HoF. Hey, five rings should be trumps.