Preventing zero-day exploits of memory vulnerabilities with guard lines

Exploitable memory errors are pervasive due to the widespread use of unsafe programming languages, such as C and C++. Despite much research, techniques for detecting memory errors at runtime have seen limited adoption due to high performance overhead, incomplete memory safety, or non-trivial microarchitectural changes. This paper describes Guard Lines, a hardware / software memory error detector that detects common types of spatial and temporal memory errors at runtime without imposing a significant performance penalty (on average only 4%). Guard Lines provides memory safety by defining certain regions of memory as inaccessible "guards," which are created in software during memory allocation. If a program ever accesses guarded memory, the hardware raises an exception indicating a memory safety violation. Guard Lines requires minimal microarchitectural changes, and it uses a novel metadata design to efficiently track the guard locations. This paper describes the design, implementation, security analysis, and performance evaluation of Guard Lines and demonstrates its feasibility to protect real-world applications against exploitable memory vulnerabilities.