Smith won't have to face 49ers cornerback Carlos Rogers, who is out again Sunday with a hamstring injury.
Smith had been listed as questionable on the injury report with a sprained ligament in his left knee. He said this week he expected to play but admitted he wasn't close to 100 percent.
Stewart was also listed as questionable with a torn medial collateral ligament and said earlier in the week he expected to play, so his deactivation was a bit of a surprise.
Stewart has now missed four straight games.
Starting defensive tackle Colin Cole (leg) is active for the Panthers.