M = 1/3 < 1 and erect image.
In a concave mirror, magnification is -ve for inverted image. Then the image can be smaller than the object. Magnification is positive but larger than 1, in case of a virtual and erect image. So given mirror is not a concave mirror.
In a convex mirror, the image is always diminished with magnification < 1 and the image is always erect. So m is positive. Hence, the given mirror is the convex mirror.