SafeDrive: Safe and recoverable extensions using language-based techniques

Abstract

We present SafeDrive, a system for detecting and recovering from type safety violations in software extensions. SafeDrive has low overhead and requires minimal changes to existing source code. To achieve this result, SafeDrive uses a novel type system that provides fine-grained isolation for existing extensions written in C. In addition, SafeDrive tracks invariants using simple wrappers for the host system API and restores them when recovering from a violation. This approach achieves fine-grained memory error detection and recovery with few code changes and at a significantly lower performance cost than existing solutions based on hardware-enforced domains, such as Nooks [33], L4 [21], and Xen [13], or software-enforced domains, such as SFI [35]. The principles used in SafeDrive can be applied to any large system with loadable, error-prone extension modules. In this paper we describe our experience using SafeDrive for protection and recovery of a variety of Linux device drivers. In order to apply SafeDrive to these device drivers, we had to change less than 4% of the source code. SafeDrive recovered from all 44 crashes due to injected faults in a network card driver. In experiments with 6 different drivers, we observed increases in kernel CPU utilization of 4–23% with no noticeable degradation in end-to-end performance.