Here. Straight from IIHF rules:
Players may be changed at any time from the players' bench, provided that the changing players shall be within an imaginary area limited by the length of the respective players' bench and three (3) meters from the boards and out of play before any change is made.
If, in the course of making a substitution, either player deliberately plays the puck while the retiring player is still on the playing surface, the infraction "Too Many Players" shall be assessed. If, in the course of a substitution, either player is accidentally struck with the puck, the play shall not be stopped and no penalty shall be assessed.
So yea. You can have 8 players on the ice so long as you don't play the puck and they're on a change and within 10 feet of the bench.