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SubjectRe: [RFC PATCH] cgroup namespaces: add a 'nsroot=' mountinfo field
Quoting Tejun Heo (tj@kernel.org):
> Hello, Serge.
>
> On Wed, Apr 13, 2016 at 01:46:39PM -0500, Serge E. Hallyn wrote:
> > It's not a leak of any information we're trying to hide. I realize
> > something like 8 years have passed, but I still basically go by the
> > ksummit guidance that containers are ok but the kernel's first priority
> > is to facilitate containers but not trick containers into thinking
> > they're not containerized. So long as the container is properly set
> > up, I don't think there's anything the workload could do with the
> > nsroot= info other than *know* that it is in a ns cgroup.
> >
> > If we did change that guidance, there's a slew of proc info that we
> > could better virtualize :)
>
> I see. I'm just wondering because the information here seems a bit
> gratuituous. Isn't the only thing necessary telling whether the root
> is bind mounted or namescoped? Wouldn't simple "nsroot" work for that
> purpose?

I don't think so - we could be in a cgroup namespace but still have
access only to bind-mounted cgroups. So we need to compare the
superblock dentry root field to the nsroot= value.

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