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- =======
- 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.enforce``". By default, it is enabled, but can be disabled at
- boot ("``loadpin.enforce=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.)
- It's also possible to exclude specific file types from LoadPin using kernel
- command line option "``loadpin.exclude``". By default, all files are
- included, but they can be excluded using kernel command line option such
- as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use
- different mechanisms such as ``CONFIG_MODULE_SIG`` and
- ``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while
- still use LoadPin to protect the integrity of other files kernel loads. The
- full list of valid file types can be found in ``kernel_read_file_str``
- defined in ``include/linux/kernel_read_file.h``.
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