The first is like Wiscampsin recommended. I have used the same method a few times. From your picture you will also need a new zipper stop on the end of one row of teeth or it is going to happen again.
The second is with a zipper repair kit. There are multitudes available on line. I have one with my tent camping supplies for emergency field repairs. I have never used it on my own tents, but have used it to fix a tent zipper for a friend while camping. My kit includes several different size slides and replacement stops. My kit is actually 2 different kits combined. The slides are open wide enough to slip the slide over both rows of teeth and move it back to where the teeth from both sides come together. Then you use a pair of pliers to squeeze the top and bottom of the slide together until you have the proper gap for the slide to move without binding. The stops are also crimped into place with the pliers.
You can work the pull on from the bottom os the zipper. It takes some time to get everything lined up, but it will go back on. My wife does sewing and alterations, and I repair zippers all the time.
had that happen to a jacket of mine once. I had to feed and interlock each tooth of the zipper one at a time to get it on the pull thingy. Took a while and if it ever happens I'll get a new jacket.
