Noninterference under Weak Memory Models

Research on information flow security for concurrent programs usually assumes sequential consistency although modern multi-core processors often support weaker consistency guarantees. In this article, we clarify the impact that relaxations of sequential consistency have on information flow security. We consider four memory models and prove for each of them that information flow security under this model does not imply information flow security in any of the other models. This result suggests that research on security needs to pay more attention to the consistency guarantees provided by contemporary hardware. The other main technical contribution of this article is a program transformation that soundly enforces information flow security under different memory models. This program transformation is significantly less restrictive than a transformation that first establishes sequential consistency and then applies a traditional information flow analysis for concurrent programs.