Re: Controlling devices and device namespaces

[Serge Hallyn]

On 09/16/2012 07:17 AM, Eric W. Biederman wrote:
> ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes:
>
> > Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> writes:
> >
> > > > One piece of the puzzle is that we should be able to allow unprivileged
> > > > device node creation and access for any device on any filesystem
> > > > for which it unprivileged access is safe.
> > >
> > > Which devices are "safe" is policy for all interesting and useful cases,
> > > as are file permissions, security tags, chroot considerations and the
> > > like.
> > >
> > > It's a complete non starter.
>
> Come to think of it mknod is completely unnecessary.
>
> Without mknod.  Without being able to mount filesystems containing
> device nodes.

Hm?  That sounds like it will really upset init/udev/upgrades in the 
container.

Are you saying all filesystems containing device nodes will need to be 
mounted in advance by the process setting up the container?

> The mount namespace is sufficient to prevent all of the
> cases that the device control group prevents (open and mknod on device
> nodes).
>
> So I honestly think the device control group is superflous, and it is
> probably wise to deprecate it and move to a model where it does not
> exist.
>
> Eric

That's what I said a few emails ago :)  The device cgroup was meant as a 
short-term workaround for lack of user (and device) namespaces.
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