Re: [PATCH v4 0/4] Introduce security_create_user_ns()

[Eric W. Biederman]

"Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> writes:

> Paul Moore <paul@xxxxxxxxxxxxxx> writes:
>
>>> I did provide constructive feedback.  My feedback to his problem
>>> was to address the real problem of bugs in the kernel.
>>
>> We've heard from several people who have use cases which require
>> adding LSM-level access controls and observability to user namespace
>> creation.  This is the problem we are trying to solve here; if you do
>> not like the approach proposed in this patchset please suggest another
>> implementation that allows LSMs visibility into user namespace
>> creation.
>
> Please stop, ignoring my feedback, not detailing what problem or
> problems you are actually trying to be solved, and threatening to merge
> code into files that I maintain that has the express purpose of breaking
> my users.
>
> You just artificially constrained the problems, so that no other
> solution is acceptable.  On that basis alone I am object to this whole
> approach to steam roll over me and my code.

If you want an example of what kind of harm it can cause to introduce a
failure where no failure was before I invite you to look at what
happened with sendmail when setuid was modified to fail, when changing
the user of a process would cause RLIMIT_NPROC to be exceeded.

I am not arguing that what you are proposing is that bad but unexpected
failures cause real problems, and at a minimum that needs a better
response than: "There is at least one user that wants a failure here".

Frankly I would love to see an argument that semantically it ever makes
sense for creating a user namespace to fail.  If that argument has
already been made, my apologies to the person who made as I missed it,
in being sick and tired, and frustrated at being blown off, when
I asked for a proper discuss of the problem at hand.

Eric