2 hours is more than enough time in the same terminal. Even 1 hour is likely enough, although I realize that may not be comfortable, especially if a flight is not on time.

As an example, United used to fly SIN-NRT-IAD, same flight number, separate planes, 40 minute connection United deemed that legal. I made it without a problem, and have made other similarly short connections without a problem. Transit security is very efficient.

In your case, Asiana and Air Canada are both Star Alliance and use Terminal 1 South.