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    SubjectRe: [RFC][PATCH 0/3] vfs: Detach mounts on unlink.
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    On Sat, Oct 5, 2013 at 5:18 PM, Rob Landley <rob@landley.net> wrote:
    >
    > Which is why containers have all sorts of extra plumbing. But that extra
    > plumbing is currently built on pivot_root(), not on chroot(). And I'd
    > dismissed pivot_root() as residue from initramfs with all that kernel thread
    > reparenting, so it seemed like the wrong tool for the job, but obviously
    > I'll take your and Al's word it's not...

    Yeah, chroot() really doesn't cut it if you allow root access - and
    thus internal chroot() calls - as you noticed (I didn't realize that
    your example was meant to be run _inside_ a chroot).

    There are generally other ways to escape chroot too if you're root.
    It's just too hard to plug. That doesn't make chroot() useless - it
    just means that the uses are elsewhere (it's useful for various
    non-security issues like development environments, but it can also be
    useful as one small _part_ of some bigger model, like a VM etc).

    pivot_root() does end up being a "better chroot than chroot" if you're
    looking for containment. It may not be a pretty system call, but it
    does avoid at least the most obvious gotchas with chroot()..

    Linus


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