The instructions to my filter says it can have air flow either way. From what I understand they work best with air pulled through them and negative pressure in the tent. In your case I would put the filter in front of the fan coming out of your tent and pull outside tent air through hood so that all smelly air goes through the carbon filter. You might not have to run a carbon if you run it to the chimney, I've heard that helps it carry away further from the home.
edit: I didn't picture your setup quite right at first, might be easiest to just stick a carbon filter in the attic and the end of the ducting or another fan with carbon filter to circulate attic air, or like orbo said.