Re: [PATCH 0/9] Multiple devpts instances

["H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>]

Serge E. Hallyn wrote:
>>
>> If you want security and permission arguments get with Serge and finish
>> the uid namespace.  The you will have a user that looks like root but
>> does not have permissions to do most things.
> 
> Right, and in particular the way it would partially solve this issue is
> that the procsys limit file would be owned by root in the initial uid
> namespace, so root in a child container would not be able to write to
> it.
> 

No, uid namespace is not the right thing for this.  If anything, it 
should be controlled by a capability flag.  This is a general issue for 
procfs and sysfs as used for controlling any kind of system resources, 
though.

> Defining a new mount option to set a per-sb limit seems useful though,
> as I could easily see wanting to limit containers (on a 1000-container
> system) to 3 ptys each for instance.

What probably would make more sense is to limit containers to a specific 
number of inodes or open file descriptors.  The pty limit was a quick 
hack to avoid DoS, but it's really equivalent (with a small multiplier, 
~3 or so) to "open inodes".

	-hpa