Micro-architectural support for metadata coherence in multi-core dynamic information flow tracking

Dynamic information flow tracking (DIFT) has shown to be an effective security measure for detecting both memory corruption attacks and semantic attacks at run-time on a wild range of systems from embedded systems and mobile devices to cloud computing. When applying DIFT to multi-thread applications running on multi-core architectures, the data processing and metadata processing are normally decoupled, i.e., being performed in different places at different times. Therefore, if the metadata access is not in the same order as data access, inconsistency issues may arise, which would reduce the security effectiveness of DIFT. Avoiding such inconsistency between data access and metadata access, i.e., maintaining metadata coherence, has become a challenging issue. In this paper, we propose METACE (METAdata Coherence Enforcement). METACE includes architectural enhancement in the memory management unit and leverages the existing cache coherence hardware and protocol to enforce metadata coherence. It introduces minimum changes to cores, coprocessors, and the memory hierarchy. It covers the complete set of data dependencies without deadlocks and is compatible with different memory consistency models. Our approach does not require modification of the source code. METACE supports out-of-order metadata access resulting in less performance degradation than previous approaches.