TLDR: Linux Lockdown mode is a security feature introduced in Linux Kernel 5.4 to restrict certain kernel functionalities, enhancing system integrity and protecting against malicious activity. By limiting kernel-level access, it helps prevent unauthorized modification of the kernel, ensuring the safety of critical systems. Lockdown mode is particularly useful for secure boot environments, servers, and embedded systems requiring robust protection.
https://en.wikipedia.org/wiki/Linux_kernel
Linux Lockdown mode operates in two levels: integrity and confidentiality. The integrity level prevents actions that could modify the kernel, such as loading unsigned modules or accessing kernel memory via `/dev/mem`. The confidentiality level extends these restrictions to prevent unauthorized reading of kernel memory. This layered approach ensures that sensitive operations and data remain protected, even if an attacker gains privileged access.
https://www.kernel.org/doc/html/latest/admin-guide/kernel_lockdown.html
The feature is tied to UEFI Secure Boot, activating automatically when the system is booted in secure mode. Administrators can also enable it manually through kernel parameters. While Lockdown mode improves security, it may restrict certain administrative tasks, making it essential to evaluate its impact on system workflows. By safeguarding the kernel's integrity, Linux Lockdown mode represents a critical advancement in modern system security.