Re: [PATCH security-next v2 00/26] LSM: Explict LSM ordering

On Thu, Sep 20, 2018 at 1:14 PM, Martin Steigerwald [off-list ref] wrote:

Kees Cook - 20.09.18, 18:23:

quoted

v2:
- add "lsm.order=" and CONFIG_LSM_ORDER instead of overloading
"security=" - reorganize introduction of ordering logic code

Updated cover letter:

This refactors the LSM registration and initialization infrastructure
to more centrally support different LSM types. What was considered a
"major" LSM is kept for legacy use of the "security=" boot parameter,
and now overlaps with the new class of "exclusive" LSMs for the future
blob sharing (to be added later). The "minor" LSMs become more well
defined as a result of the refactoring.

Instead of continuing to (somewhat improperly) overload the kernel's
initcall system, this changes the LSM infrastructure to store a
registration structure (struct lsm_info) table instead, where metadata
about each LSM can be recorded (name, flags, order, enable flag, init
function). This can be extended in the future to include things like
required blob size for the coming "blob sharing" LSMs.

I read the cover letter and still don´t know what this is about. Now I
am certainly not engaged deeply with LSM. I bet my main missing piece
is: What is a "blob sharing" LSM.

I think it would improve the cover letter greatly if it explains briefly
what is a major LSM, what is a minor LSM and what is a "blob sharing"
LSM.

Why those are all needed? What is the actual security or end user
benefit of this work? The questions are not to question your work. I bet
it makes all perfect sense. I just did not understand its sense from
reading the cover letter.

Sure, thanks! I'll include more details for any later versions. This
is mainly related to some internal refactoring the LSM is doing to
support additional LSM that need more extensive "stacking" of the
kernel internals. I aimed this at linux-doc@ and linux-arch@ to get
feedback on the Documentation/ and linker script changes,
respectively. In theory, users don't need to know anything about
minor/major nor blob-sharing, as that should normally be all an
internal issue.

Thanks!

-Kees

-- 
Kees Cook
Pixel Security