Re: [PATCH v4 0/2] Add further ioctl() operations for namespace discovery

From: Eric W. Biederman
Date: Wed Jan 25 2017 - 23:28:23 EST

"Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx> writes:

> On 25 January 2017 at 15:28, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:

>> My concern is that the difference between returning -EOVERFLOW and
>> overflow_uid is primarily about usability. If you haven't played with
>> the usability I don't trust that we have made the proper trade off.
> So, I had not initially included the no-UID-mapping case, and when you
> proposed -EOVERFLOW for that case, it seemed better.
> On reflection, mapping to the overflow_uid seems simpler. Taking the
> example shown in my other mail a short time ago, the unmapped UID 0
> from the outer namespace would map to the overflow_uid (which UID my
> program would print), but my program would still correctly report that
> the UID 0 process in the outer namespace might (subject to LSM checks)
> have capabilities in the inner namespace.
> So, it seems that reverting the EOVERFLOW change is in order (and my
> example program thus needs no changes). Does that sound reasonable to
> you?

It does. I just care that you have thought through the tradeoffs of
that corner of the interface design.