The 6-8, 318-pound Farris replaces Tim Stuber, who was terminated from the practice squad.
The 25-year-old St. Paul, Minn., native signed with Buffalo as a free agent in 2001 and played in three games, with one start, before suffering a fractured leg in Week Three at Pittsburgh that ended his season.
Farris spent the entire '99 season on injured reserve with a foot injury and also missed the entire 2000 season.
As a collegian, Farris won the Outland Trophy as the nation's premierlineman in 1998 and was a unanimous first-team All-America selection.
Farris has been assigned jersey number 77.