Re: [lxc-devel] [RFC PATCH 11/11] loop: Allow priveleged operations for root in the namespace which owns a device

[Seth Forshee <seth.forshee@canonical.com>]

On Mon, May 26, 2014 at 11:32:05AM -0400, Michael H. Warfield wrote:
> On Mon, 2014-05-26 at 11:16 +0200, Seth Forshee wrote:
> > On Fri, May 23, 2014 at 08:48:25AM +0300, Marian Marinov wrote:
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> > > 
> > > One question about this patch.
> > > 
> > > Why don't you use the devices cgroup check if the root user in that namespace is allowed to use this device?
> > > 
> > > This way you can be sure that the root in that namespace can not access devices to which the host system did not gave
> > > him access to.
> 
> > That might be possible, but I don't want to require something on the
> > host to whitelist the device for the container. Then loop would need to
> > automatically add the device to devices.allow, which doesn't seem
> > desirable to me. But I'm not entirely opposed to the idea if others
> > think this is a better way to go.
> 
> I don't see any safe way to avoid it.  The host has to be in control of
> what devices can and can not be accessed by the container.

Hmm, for testing I've been giving access to 7:* block devices since my
containers can't mknod and only see device nodes for loop devices they
have access to, but maybe I'm not being sufficiently paranoid.