Blinder: Partition-Oblivious Hierarchical Scheduling

Hierarchical scheduling enables modular reasoning about the temporal behavior of individual applications by partitioning CPU time and thus isolating potential misbehavior. However, conventional time-partitioning mechanisms fail to achieve strong temporal isolation from a security perspective; variations in the executions of partitions can be perceived by others, which enables an algorithmic covert timing-channel between partitions that are completely isolated from each other in the utilization of time. Thus, we present a run-time algorithm that makes partitions oblivious to others' varying behaviors even when an adversary has full control over their timings. It enables the use of dynamic time-partitioning mechanisms that provide improved responsiveness, while guaranteeing the algorithmic-level non-interference that static approaches would achieve. From an implementation on an open-source operating system, we evaluate the costs of the solution in terms of the responsiveness as well as scheduling overhead.