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SubjectRe: Detecting if you are running in a container
On Tue, Oct 11, 2011 at 02:16:24PM -0700, Eric W. Biederman wrote:
> It actually isn't much complexity and for the most part the code that
> I care about in that area is already merged. In principle all I care
> about are having the identiy checks go from:
> (uid1 == uid2) to ((user_ns1 == user_ns2) && (uid1 == uid2))
> There are some per subsystem sysctls that do make sense to make per
> subsystem and that work is mostly done. I expect there are a few
> more in the networking stack that interesting to make per network
> namespace.
> The only real world issue right now that I am aware of is the user
> namespace aren't quite ready for prime-time and so people run into
> issues where something like sysctl -a during bootup sets a bunch of
> sysctls and they change sysctls they didn't mean to. Once the
> user namespaces are in place accessing a truly global sysctl will
> result in EPERM when you are in a container and everyone will be
> happy. ;)
> Where all of this winds up interesting in the field of oncoming kernel
> work is that uids are persistent and are stored in file systems. So
> once we have all of the permission checks in the kernel tweaked to care
> about user namespaces we next look at the filesystems. The easy
> initial implementation is going to be just associating a user namespace
> with a super block. But farther out being able to store uids from
> different user namespaces on the same filesystem becomes an interesting
> problem.

Yipes. Why would anyone want to do that?


> We already have things like user mapping in 9p and nfsv4 so it isn't
> wholly uncharted territory. But it could get interesting. Just
> a heads up.

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