LSM: LoadPin for kernel file loading restrictions

This LSM enforces that kernel-loaded files (modules, firmware, etc)
must all come 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.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
diff --git a/security/loadpin/Kconfig b/security/loadpin/Kconfig
new file mode 100644
index 0000000..c668ac4
--- /dev/null
+++ b/security/loadpin/Kconfig
@@ -0,0 +1,10 @@
+config SECURITY_LOADPIN
+	bool "Pin load of kernel files (modules, fw, etc) to one filesystem"
+	depends on SECURITY && BLOCK
+	help
+	  Any files read through the kernel file reading interface
+	  (kernel modules, firmware, kexec images, security policy) will
+	  be pinned to the first filesystem used for loading. Any files
+	  that come from other filesystems will be rejected. This is best
+	  used on systems without an initrd that have a root filesystem
+	  backed by a read-only device such as dm-verity or a CDROM.