[PATCH review 12/16] userns: For /proc/self/{uid, gid}_map derive the lower userns from the struct file

[Eric W. Biederman]

Serge Hallyn <serge.hallyn at canonical.com> writes:

> Quoting Eric W. Biederman (ebiederm at xmission.com):
>> 
>> In practice when playing around it is the difference between.
>> unshare -U /bin/bash
>> echo 0 1000 1 > /proc/self/uid_map
>> 
>> And the need to pre-plan something.  You can set the uid_map from the
>> parent in a shell script but it is a real pain.  So for just messing
>> around allowing seq_ns == ns is a real advantage.
>
> Heh, ok - I almost always want >1 uid mapped, but I can see the
> advantage.

The original plan called for an upcall and >1 uid mapped.  But yeah
that is something else again.

> Thanks.
>
> I don't recall whether I put this in originally, but
>
> Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
>
>> > I also wonder if -EINVAL would be a more appropriate choice here.
>> > We're trying to keep things sane, rather than saying "not allowed"
>> > for its own sake.
>> 
>> A different error code might be better.
>
> I suppose strictly speaking (looking at errno-base.h) it would be
> EBADF?

Definitely not EBADF.  EBADF is the error code for operating on a closed
file descriptor.

I want a ENOTALLOWED. Anyway.

Eric