[PATCH v7 0/6] Safe LSM (un)loading, and immutable hooks

Casey Schaufler casey at schaufler-ca.com
Mon Apr 30 16:46:55 UTC 2018

On 4/30/2018 9:11 AM, Sargun Dhillon wrote:
> On Sun, Apr 29, 2018 at 2:23 PM, Casey Schaufler <casey at schaufler-ca.com> wrote:
>> On 4/29/2018 4:49 AM, Tetsuo Handa wrote:
>>> Casey Schaufler wrote:
>>>> I think that we're on the verge of having a major merge collision.
>>> I think that the reason of major merge collision is that your patchset is
>>> too big to review.
>> My patch set is large because it has to address all of the
>> aspects of multiple modules running on the system before some
>> important members of the community will look at it seriously.
>>>   > That's a lot of overhead. The smaller the patches, the more work
>>>   > required to make the patch set. You're right that the current patches
>>>   > are too big. Moving forward I will be providing smaller, easier to
>>>   > deal with patches. The sheer overhead of rebaseing a large patch set
>>>   > has slowed down the development considerably. Minions. What I need are
>>>   > minions.
>>> You are holding the global lock for patchset which you did not get response.
>>> If you agree with breaking into smaller patches, we will be able to solve
>>> the major merge collision.
>> I will be presenting the set of smaller patches once I finish merging
>> them into 4.18. It's a bigger jobs than usual because of the change from
>> lists to hlists, the significant changes to AppArmor and the early stages
>> of SELinux namespacing. I hope to have it done mid week, but the changes
>> need to get tested, and there are lots of configurations involved.
>> I am perfectly amenable to the patches going in in logical stages.
>> In fact, that is what I would recommend.
> I guess I'm just a little bit frustrated, because, in my mind, some of
> my patches provide immediate value, and are ready to be reviewed, and
> or respun. Testuo did a good job reviewing 1-5, and I think that if
> those are his only issues, then we're good to go.
> I've:
> 1) Do safe hook loading for sane security modules (those that don't
> try to overload major hooks), without compromising the security of
> other hooks
> 2) Suggested a whitelist of major hooks to prevent insane modules from
> being loaded
> If Casey's patches land, we can just not do (2), and we're good to go.

I understand your frustration. As much as I would like to
avoid having the stacking work take any longer than it already
has (I *do* have a boatload of other stuff I want to get done)
I suggest that if you can get consensus that the lkm-based
security module work should be accepted that you go forward and
get it in. I know that I have at least one major round of review
before the stacking can really be seriously considered. I knew
the job was dangerous when I took it.

>>>> ...
> One dumb use case I have is the ability to limit interactions with
> PTYs for containerized applications. Another aspect of this is being
> able to write policies in C, and actually being able to control the
> nitty gritty of what's going on, versus actively fighting with the
> LSM(s).

You don't need lkm-based modules to do that, but I can see
why you might want to do it that way. It's also something that
I would expect LandLock to be a solution for, but again you'd
need to be running LandLock when you identified the issue.

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