The victory kept Arsenal at the top of the table while Sunderland's day was summed up when they lost first-choice keeper Thomas Sorensen after 15 minutes with a suspected dislocated elbow.
Kanu, making his 100th Premiership appearance, hooked in a third minute rebound after Freddie Ljungberg caused confusion at a near post corner.
Sunderland showed more spirit after the interval and Jody Craddock headed an 83rd-minute goal from Kevin Kilbane's cross.
But manager Peter Reid admitted after the match: "We didn't make Arsenal work. We defended poorly for their first goal and we missed a tackle for their second.
"The game was all over by half time. Then Arsenal took their foot off the pedal."
In-form Kanu said: "There's so much confidence in our dressing room. I'm very happy to be scoring regularly. It's been very important to me to start regularly again."