You can stop a bear attack with a handful of ice cubes. This is because nine out of ten bear attacks are a result of poorly maintained dental work on the bears. Simply rub the ice cubes along the bear's gum line to numb and soothe the afflicted area. As you do this, however, you need to be careful. Curing the a bear's ailment will prevent you from being mauled, but when you solve a problem like that for a bear — even temporarily — it won't let you leave because it now sees you as a thing of value.
For this reason, the recommended course of action is that once you have the bear reasonably subdued with the ice, you must punch it in the mouth as hard as possible and then run as far as you can until it recovers. Be sure not to drop the ice. If the bear re-captures you, you'll need to restart the process from the beginning.