[PATCH] devpts: Make ptmx be owned by the userns owner instead of userns-local 0

[Andy Lutomirski]

On Mar 14, 2016 1:35 AM, "Serge Hallyn" <serge.hallyn at ubuntu.com> wrote:
>
> Quoting Andy Lutomirski (luto at kernel.org):
> > We used to have ptmx be owned by the inner uid and gid 0.  Change
> > this: if the owner and group are both mapped but are not both 0,
> > then use the owner instead.
> >
> > For container-style namespaces (LXC, etc), this should have no
> > effect -- UID 0 is will either be the owner or will be unmapped.
>
> This doesn't seem right - it's often the case that the owner is mapped
> in as non-0 uid, safe or not.  The actual namespace root uid should be
> the owner (so long as it exists).
>
> Why not reverse the cases?  If 0 is not mapped, then check whether the
> current_user_ns()->owner is mapped?

Good point, and less chance of breakage that way as well.

--Andy