The pattern is the Ilene Market Bag by Hannah Ingalls, free to download from her blog, iknityouknot. It's a stretchy, single strap market bag that is knit from the bottom up. While the bottom is knit flat, stitches are picked up from around the sides of the base and it is knit in a circle up to the top of the bag before going back to flat knitting for the strap.
