The Detroit Lions activated cornerback season limit of 53 players.
Smith recorded 39 tackles and five interceptions in 12 games (10 starts) last season, his first with the Lions after they acquired him from Denver. He has been sidelined with a broken foot.
Harris has been the Lions' regular punter since 2003, but was released with 23-year-old rookie Ryan Donahue also on the roster.
Also released Saturday were wide receivers Dominique Barnes, Nate Hughes, Tim Toone and Derrick Williams; defensive tackles Rob Callaway and Quinn Pitcock; linebackers Caleb Campbell and Cobrani Mixon (waived/injured); tackle Kirk Chambers; running backs Matt Clapp and Ian Johnson; defensive ends Keyunta Dawson and Narada Williams; tight ends Joe Jon Finley and Gijon Robinson; defensive backs Aaron Francisco, Anthony Madison, Prince Miller, Paul Pratt, Ricardo Silva and Nathan Vasher; centers Dan Gerberry and Rudy Niswanger; quarterback Zac Robinson; and guard Donald Thomas.
Detroit placed tackle Johnny Culbreath injured reserve as well.