[PATCH 2/2] doc: LSM: fix module ordering description for /sys/kernel/security/lsm

[Lincoln Wallace]

The LSM usage document states that the capability module will always
be first in /sys/kernel/security/lsm, followed by any "minor" modules
and then the one "major" module.

This does not match the current LSM infrastructure:

 - When CONFIG_SECURITY_LOCKDOWN_LSM_EARLY is enabled, lockdown is
   initialized as an early LSM, before all other modules including
   capability, and appears first in the list.

 - The integrity modules (e.g. IMA and EVM) register with
   LSM_ORDER_LAST and are always placed at the end of the list,
   regardless of the position of the major module.

 - The relative order of the remaining modules is not fixed by the
   framework; it follows CONFIG_LSM or the "lsm=" kernel command
   line parameter.

Rewrite the paragraph to describe the actual ordering: lockdown
first when early lockdown is enabled, capability otherwise,
integrity modules at the end, and the remaining modules in the
configured order.

Signed-off-by: Lincoln Wallace <locnnil0@xxxxxxxxx>
---
 Documentation/admin-guide/LSM/index.rst | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst
index c24310c709dc..9518495edfbc 100644
--- a/Documentation/admin-guide/LSM/index.rst
+++ b/Documentation/admin-guide/LSM/index.rst
@@ -27,9 +27,15 @@ man-pages project.
 A list of the active security modules can be found by reading
 ``/sys/kernel/security/lsm``. This is a comma separated list, and
 will always include the capability module. The list reflects the
-order in which checks are made. The capability module will always
-be first, followed by any "minor" modules (e.g. Yama) and then
-the one "major" module (e.g. SELinux) if there is one configured.
+order in which checks are made. The capability module will be
+first, unless CONFIG_SECURITY_LOCKDOWN_LSM_EARLY is enabled, in
+which case the lockdown module will precede it. The integrity
+modules (e.g. IMA and EVM), if enabled in the kernel
+configuration, are always placed at the end of the list. Any
+other "minor" modules (e.g. Yama) and the one "major" module
+(e.g. SELinux), if there is one configured, appear in between,
+in the order given by CONFIG_LSM or the ``"lsm=..."`` kernel
+command line parameter.
 
 Process attributes associated with "major" security modules should
 be accessed and maintained using the special files in ``/proc/.../attr``.
-- 
2.53.0