Did you rinse the rub off the loin before smoking? Did you do a fry test? I don't fry test always, but with pork loins, Canadian bacon, pork belly bacon, or pork butt bacon, I always fry test. Salt can make or break a smoke. Next time, fry test and if its too salty, soak in water for an hour or so while changing the water out with fresh water a couple times and fry test again after to make sure.
Most likely you had to much salt in the rub / or combined with / to long of a brine, plus, without desalinating it & doing a fry test; additionally - your chips were too much and burnt at high temps causing the white smoke as said above..