You Shall Not Bypass: Employing data dependencies to prevent Bounds Check Bypass

TL;DR

This paper investigates methods to delay vulnerable instructions in Bounds Check Bypass attacks, reducing overhead compared to full serialization, by exploring alternatives to existing speculative load hardening techniques.

Contribution

It introduces alternative delay techniques for vulnerable instructions that lower performance overhead compared to serialization-based mitigations.

Findings

Proposed delay methods cause 60% overhead on Phoenix benchmark

Full serialization causes 440% slowdown

Alternative methods outperform serialization in efficiency

Abstract

A recent discovery of a new class of microarchitectural attacks called Spectre picked up the attention of the security community as these attacks can circumvent many traditional mechanisms of defense. One of the attacks---Bounds Check Bypass---can neither be efficiently solved on system nor architectural levels and requires changes in the application itself. So far, the proposed mitigations involved serialization, which reduces the usage of CPU resources and causes high overheads. In this report, we explore methods of delaying the vulnerable instructions without complete serialization. We discuss several ways of achieving it and compare them with Speculative Load Hardening, an existing solution based on a similar idea. The solutions of this type cause 60% overhead across Phoenix benchmark suite, which compares favorably to the full serialization causing 440% slowdown.