LPAH: Illustrating Efficient Live Patching With Alignment Holes in Kernel Data

The Linux kernel is regularly updated to enhance security, improve performance, and introduce new functionalities. Traditional updating methods typically require rebooting, leading to service disruptions and potential data loss. Live-patching technology dynamically updates the kernel modules without rebooting, ensuring continuous service availability. However, this technique has its drawbacks. Since live-patching alters the original structure of data types, it can no longer utilize base offsets to access the members, imposing considerable overheads. This paper proposes LPAH (Live Patching with Alignment Holes), a live patching system that leverages the fragmented space generated by compile-time alignment for data types, to enable effective live patching updates for security vulnerability fixes, feature enhancements, and user-defined patching tasks. LPAH capitalizes on the relationship between these alignment holes and data objects. This approach ensures efficient access to extended data members while preserving the original data's integrity. This approach allows other functions to remain unaffected by updates and replacements through explicit type casts. Extensive experimental results show that LPAH offers valid and robust live patching for multiple real vulnerabilities in the Linux kernel, without degrading performance. Our method provides an efficient way to install security patches in the Linux kernel, and thus reenforces kernel security.