It's understandable since 擂る is 常用外 and usually written in hiragana. The noun form is ゴマすり(ゴマをすること or ゴマをする人), which is also commonly used, shows that it's not する "to do", though.
Incidentally, these two する have different pitch accents. The accent is on the first syllable in 擂る (type1 /す]る/), whereas する "to do" is flat (type0 /する=/).