Messages in this thread | | | From | (Eric W. Biederman) | Date | Wed, 25 Jan 2017 15:28:27 +1300 | Subject | Re: [PATCH v4 0/2] Add further ioctl() operations for namespace discovery |
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ebiederm@xmission.com (Eric W. Biederman) writes:
> "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes: > >> Hi Eric, >> >> On 25 January 2017 at 14:58, Eric W. Biederman <ebiederm@xmission.com> wrote: >>> "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes: >>> >>>> I would like to write code that discovers the namespace setup on a live >>>> system. The NS_GET_PARENT and NS_GET_USERNS ioctl() operations added in >>>> Linux 4.9 provide much of what I want, but there are still a couple of >>>> small pieces missing. Those pieces are added with this patch series. >>> >>> So it looks like the -EOVERFLOW change broke your example program. >>> Causing it to abort if -EOVERFLOW is hit. Do we really want to return >>> -EOVERFLOW? Or do you want to fix your program? >> >> Bother! Yes, I should have kept the example program in sync. (I >> overlooked that it was not any more in sync.) >> >> So, I want to make sure I understand correctly, before I aswer your >> question. Suppose we have >> >> 1. Outer namespace owned by UID 0 >> 2. Inner namespace owned by UID 1000 >> 3. A UID mapping in the inner namespace that maps '0 1000 1' >> 4. A processs, X, in the outer namespace with UID 0 (and all caps). >> >> That's the case you're meaning, right? > > I think so I just noticed you did not handle -EOVERFLOW in > the one NS_GET_OWNER_UID call. > >> So, UID 0 doesn't have a >> mapping into the inner namespace, but does have all capabilities in >> that inner namespace, right? > > That is correct.
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.
Eric
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