NAK: user namespace delta for raring?

[Serge Hallyn]

Quoting Serge Hallyn (serge.hallyn at canonical.com):
> Quoting Eric W. Biederman (ebiederm at xmission.com):
> > A big chunk of my devpts patches are to resolve the newinstance
> > /dev/ptmx mess.  I forget all of the details of why that is a problem.
> > How to sort out that mess is a problem, substantial and maybe a little
> > controversial.
> > 
> > The basics of allowing devpts to be mounted with user namespace
> > permissions should be a trivial few additional lines of code.
> 
> There certainly are weirdnesses - in particular that 'mount -t devpts'
> without newinstance, even after mounting a newinstance, will get you
> the init devpts instance back.  And that the /dev/ptmx device, if not
> bind-mounted from /dev/pts, gets you the host instance.  But we work
> around the former by refusing devpts mounts in the container altogether
> using apparmor (not ideal, but works), and the latter, of course by
> bind-mounting /dev/pts/ptmx.
> 
> So while those address a real problem that would be good to have
> fixed, you might be right that we might be able to drop them.  I
> could test a kernel without those patches and see if there is some
> issue I'm forgetting that prevents containers from starting.

Woohoo - yes, using a kernel from
git://kernel.ubuntu.com/serge/quantal-userns.git branch
master-next.jan14.userns.shortened, I can still run ubuntu containers
in a userns just fine.  This has the following patches removed:

linux (3.8.0-0.1userns2) raring; urgency=low

  * Remove some patches:
    - 5cc374f: proc: Kill dead code in proc_fill_cache
    - 9dac985: vfs: Fix weird nfs revalidate problem.
    - d4853ad: devpts: Remove unnecessary compatibility code
    - 09e8dc6: devpts: Update the documentation
    - 7736dad: devpts: Remove the internal mount.
    - cb1917a: devpts: kill pts_sb_from_inode
    - 5285622: devpts: Remove the devpty cleanup special case.
    - 58cbf60: devpts: Rename /dev/ptmx /dev/pts/ptmx
    - 02ae468: devpts: Make ptmx a symlink to pts/ptmx on devtmpfs
    - 753aaf4: devpts: Make the newinstance option historical
    - 03c7dff: devpts: Remove CONFIG_DEVPTS_MULTIPLE_INSTANCES
    - 9bc0f7d: devpts: Set the default permissions of /dev/pts/ptmx and /dev/ptmx to 0666

 -- Serge Hallyn <serge at tangerine.buildd>  Fri, 18 Jan 2013 20:24:11 +0000

-serge