You could use canvas cement and sail tape. Clean the canvas, put cement and sail tape on each side of the tear. Make sure the tape is cut in the shape of an oval. Its amazing how strong that stuff is. Can be bought at any West Marine, but you may have issues finding it in OD.
OR
Go to a leather shop and buy of those awl threaders. They work great on canvas. I used on all the time when I was crewing on a tall ship. One of these:
Way easier to make consistant stitches then a curved needle. Just remember to use a stout waxed thread. I like hemp, if you can find it. Nylon "synue" also works well, but no idea how it fares in the sun.
Zach