Gionta also assisted on the Habs' other goal -- a first-period, power-play tally by Andrei Kostitsyn -- and Montreal won on home ice for the sixth time in seven games.
Tomas Plekanec added two assists and Carey Price didn't allow a score until the final minutes, turning aside 35 shots for the win, his 14th victory of the season.
The Sabres got their only goal from Jordan Leopold. Ryan Miller let in three goals on 33 shots in the setback, the fourth in six games for Buffalo.
Senate Democrats to pull all-nighter on climate change
Interpol investigating stolen passports on missing flight