Linux Landlock LSM Lets Unprivileged Users Sandbox Apps Without Root Access

Landlock is a Linux Security Module introduced in kernel version 5.13 that allows processes to restrict their own filesystem access without requiring root privileges or administrator intervention. Unlike established security frameworks such as SELinux or AppArmor, Landlock is designed for simplicity, enabling developers to define per-process access rules using straightforward system calls like landlock_add_rule(). Rules are strictly additive in restriction — once set, they can only further limit access and cannot be reversed or expanded during a process's lifetime. A practical use case includes sandboxing a browser process to a single temporary directory when rendering potentially unsafe email attachments, eliminating the need for full virtual machines or containers. However, Landlock covers only filesystem access controls and does not protect against network-based attacks or other threat vectors, so careful rule planning is essential.