Legally, when you've got the Canadian citizenship, your Chinese passport is no longer valid, no matter what expire date is.
Most likely, the Chinese custom will not know that you became Canadian citizen(and automatically abandoned the Chinese citizenship) and allow you in and out, as long as your passport and immigration paper appear to be "valid".
The Canadian immigration will probably allow you in even they know you've got the citizenship, because Canada recognizes dual citizenship.
So the question is whether Chinese border knows your status or not. I'll not bet on they don't know and risk to travel, but I think some people will and they did so without problems.
To be a Canadian citizen you need to know what is lawful and what is not, and to be a law-abiden citizen.