32 lines
1.6 KiB
ReStructuredText
32 lines
1.6 KiB
ReStructuredText
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=======
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LoadPin
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=======
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LoadPin is a Linux Security Module that ensures all kernel-loaded files
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(modules, firmware, etc) all originate from the same filesystem, with
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the expectation that such a filesystem is backed by a read-only device
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such as dm-verity or CDROM. This allows systems that have a verified
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and/or unchangeable filesystem to enforce module and firmware loading
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restrictions without needing to sign the files individually.
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The LSM is selectable at build-time with ``CONFIG_SECURITY_LOADPIN``, and
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can be controlled at boot-time with the kernel command line option
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"``loadpin.enforce``". By default, it is enabled, but can be disabled at
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boot ("``loadpin.enforce=0``").
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LoadPin starts pinning when it sees the first file loaded. If the
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block device backing the filesystem is not read-only, a sysctl is
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created to toggle pinning: ``/proc/sys/kernel/loadpin/enabled``. (Having
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a mutable filesystem means pinning is mutable too, but having the
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sysctl allows for easy testing on systems with a mutable filesystem.)
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It's also possible to exclude specific file types from LoadPin using kernel
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command line option "``loadpin.exclude``". By default, all files are
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included, but they can be excluded using kernel command line option such
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as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use
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different mechanisms such as ``CONFIG_MODULE_SIG`` and
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``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while
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still use LoadPin to protect the integrity of other files kernel loads. The
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full list of valid file types can be found in ``kernel_read_file_str``
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defined in ``include/linux/kernel_read_file.h``.
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