Live-patching security vulnerabilities inside the Linux kernel with eBPF Linux Security Module

This post introduces the use of eBPF (extended Berkeley Packet Filters) as a Linux Security Module (LSM) to implement granular security policies directly within the Linux kernel. Specifically, it demonstrates how LSM BPF can be used to prevent privilege escalation by blocking unprivileged users from creating new user namespaces via the `unshare` syscall, a vulnerability that has been difficult to address in the mainline kernel. This represents an advancement in Cloudflare's ability to dynamically enforce security policies and patch vulnerabilities without requiring kernel modifications or custom kernel modules, thereby enhancing its threat management capabilities.