Preheat the oven to 350 degrees.
Grease a 9x13 baking pan.
In a mixing bowl cream together the butter and sugar together.
Add the flour, salt, baking soda, eggs, vanilla, and milk. Mix well.
Lastly, mix in the mashed bananas.
Pour batter into the greased baking pan.
Bake for 30 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and cool.
While the bars are baking mix the softened cream cheese until smooth. Add the butter and mix well.
Add in the vanilla, powdered sugar, and the milk. Mix until smooth.
When the bars are cooled, spread on the cream cheese frosting.