LoadPin

LoadPin is a Linux Security Module that ensures all kernel-loaded files (modules, firmware, etc) all originate from the same filesystem, with the expectation that such a filesystem is backed by a read-only device such as dm-verity or CDROM. This allows systems that have a verified and/or unchangeable filesystem to enforce module and firmware loading restrictions without needing to sign the files individually.

The LSM is selectable at build-time with CONFIG_SECURITY_LOADPIN, and can be controlled at boot-time with the kernel command line option “loadpin.enabled”. By default, it is enabled, but can be disabled at boot (“loadpin.enabled=0”).

LoadPin starts pinning when it sees the first file loaded. If the block device backing the filesystem is not read-only, a sysctl is created to toggle pinning: /proc/sys/kernel/loadpin/enabled. (Having a mutable filesystem means pinning is mutable too, but having the sysctl allows for easy testing on systems with a mutable filesystem.)