Re: [PATCH v3 1/3] security: Introduce LSM_ORDER_LAST and set it for the integrity LSM

[Mimi Zohar]

On Fri, 2023-03-10 at 17:33 +0100, Roberto Sassu wrote:
> On Fri, 2023-03-10 at 11:22 -0500, Paul Moore wrote:
> > On Fri, Mar 10, 2023 at 8:39 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
> > > On Thu, 2023-03-09 at 17:04 -0500, Paul Moore wrote:
> > > > On Thu, Mar 9, 2023 at 8:21 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
> > > > > On Thu, 2023-03-09 at 09:54 +0100, Roberto Sassu wrote:
> > > > > > From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> > > > > > 
> > > > > > Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs needing to be
> > > > > > last, e.g. the 'integrity' LSM, without changing the kernel command line or
> > > > > > configuration.
> > > > > > 
> > > > > > Also, set this order for the 'integrity' LSM. While not enforced, this is
> > > > > > the only LSM expected to use it.
> > > > > > 
> > > > > > Similarly to LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled
> > > > > > and put at the end of the LSM list.
> > > > > > 
> > > > > > Finally, for LSM_ORDER_MUTABLE LSMs, set the found variable to true if an
> > > > > > LSM is found, regardless of its order. In this way, the kernel would not
> > > > > > wrongly report that the LSM is not built-in in the kernel if its order is
> > > > > > LSM_ORDER_LAST.
> > > > > > 
> > > > > > Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
> > > > > > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> > > > > 
> > > > > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> > > > 
> > > > Warning: procedural nitpicking ahead ...
> > > > 
> > > > The 'Signed-off-by' tag is in reference to the DCO, which makes sense
> > > > to add if you are a patch author or are merging a patch into a tree,
> > > > but it doesn't make much sense as a ACK/thumbs-up; this is why we have
> > > > the 'Acked-by' and 'Reviewed-by' tags.  I generally read the
> > > > 'Acked-by' tag as "I'm the one responsible for a chunk of code
> > > > affected by this patch and I'm okay with this change" and the
> > > > 'Reviewed-by' tag as "I looked at this patch and it looks like a good
> > > > change to me".  Perhaps surprisingly to some, while an 'Acked-by' is a
> > > > requirement for merging in a lot of cases, I appreciate 'Reviewed-by'
> > > > tags much more as it indicates the patch is getting some third-part
> > > > eyeballs on it ... so all you lurkers on this list, if you're
> > > > reviewing patches as they hit your inbox, don't be shy about posting
> > > > your 'Reviewed-by' tag if your comfortable doing so, we all welcome
> > > > the help :)
> > > > 
> > > > https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin
> > > 
> > > In this case, it was a bit unclear who actually was going to upstream
> > > this patch set.
> > 
> > FWIW, I wasn't expecting to see your sign-off without a note that you
> > had merged it.  Normally I would have expected either an acked-by or a
> > note that you had merged it, a sign-off without a merge notice seemed
> > a little odd to me so I thought I would mention the above :)  No harm
> > either way, I just figured a little discussion on process might not be
> > a terrible idea to make sure we are all on the same page.
> > 
> > > It's better that you upstream it,  but since this
> > > affects subsequent IMA and EVM patches, please create a topic branch.
> > 
> > I generally don't do topic branches for work that has been merged into
> > a -next or -stable branch. I prefer to limit topic branches to
> > special-cases where there is some value in keeping a central branch
> > for multiple people to coordinate while the patchset is still in
> > development; once a patchset has progressed far enough to be merged
> > into a -stable or -next branch I stop maintaining the topic branch.

I'm definitely not the expert in this, but topic branches normally need
to remain around until they make it into a release or an -rc, not
-next.

> > 
> > In this particular case the changes to the IMA/EVM code looked very
> > minor, so I doubt there would be a significant merge conflict with the
> > IMA/EVM tree during this development cycle, but if you would prefer to
> > take this patchset via the IMA/EVM tree that is okay with me; just let
> > me know so I can ACK the two LSM-related patches (I'm going to review
> > the latest posting today).
> 
> Probably it would be beneficial if you carry this patch set, so that
> the next 'evm: Do HMAC of multiple per LSM xattrs for new inodes', and
> 'security: Move IMA and EVM to the LSM infrastructure' could be applied
> on top (assuming that we are able to finish within this cycle).

That's fine.

> 
> > As a bit of an aside, while this doesn't cover topic branches (once
> > again, I consider those special cases), when managing the LSM tree I
> > follow the process that is documented here:
> > 
> > https://github.com/LinuxSecurityModule/kernel/blob/main/README.md
> > 
> > [NOTE: the above GH repo is a read-only mirror of the canonical LSM
> > kernel.org repo, it just happens that GH does a better job rendering
> > txt]
> > 
> > The main LSM repo process "docs" / pointers can be found in the main
> > README or "about" page:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git/about
> > 
> > If people have suggestions for a different approach to managing the
> > LSM tree I'm always open to discussion.

Thank you for the pointer.  Nicely written.

-- 
thanks,

Mimi