A critical RCU safety property is... ease of use

Some might argue that read-copy update (RCU) is too low-level to be targeted by hackers, but the advent of Row Hammer [19] demonstrated the naivete of such views. After all, if black-hat hackers are ready, willing, and able to exploit hardware bugs such as Row Hammer, they are assuredly ready, willing, and able to exploit bugs in RCU. Nor is it any longer the case that RCU's involvement in exploitable Linux-kernel bugs is strictly theoretical. However, this bug involved not RCU's correctness, but rather its ease of use. Nevertheless, it was a real bug that really needed fixing. This paper describes this bug and the road to its eventual fix.