My favourite contribution to the Linux kernel, which I witnessed myself, was a 1-character fix to a macro that my boss found, related to reading ADC, and which we spent two weeks checking and double-checking and re-double-checking to be sure that it was actually a bug.
It was, he submitted it, and that one character fix got him into the contributors file .. we were all highly amused, because that particular boss didn't program much, but found the bug during testing and it was, nevertheless, a huge win for him .. ;)
EDIT: it was a 2-character fix. ;)
https://lkml.iu.edu/2103.2/08109.html
(W., if you read this, I still love telling the story of how you found this bug..)