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    Subjectuserns: targeted capabilities v5
    Here is a repost of my previous user namespace patch, ported onto
    last night's git head.

    It fixes several things I was doing wrong in the last (v4)
    posting, in particular:

    1. don't set uts_ns->user_ns to current's when !CLONE_NEWUTS
    2. add a ipc_ns->user_ns which owns ipc_ns, and use that to
    decide CAP_IPC_OWNER
    3. fix logic flaw caused by bad parantheses
    4. allow do_prlimit to current
    5. don't always give root full privs to init_user_ns

    The expected course of development for user namespaces is laid out
    at https://wiki.ubuntu.com/UserNamespace. Bugs aside, this
    patchset is supposed to not at all affect systems which are not
    actively using user namespaces, and only restrict what tasks in
    child user namespace can do. They begin to limit privilege to
    a user namespace, so that root in a container cannot kill or
    ptrace tasks in the parent user namespace, and can only get
    world access rights to files. Since all files currently belong
    to the initila user namespace, that means that child user
    namespaces can only get world access rights to *all* files.
    While this temporarily makes user namespaces bad for system
    containers, it starts to get useful for some sandboxing.

    I've run the 'runltplite.sh' with and without this patchset and
    found no difference. So all in all, this is the first version
    of this patchset for which I feel comfortable asking: please
    consider applying.

    thanks,
    -serge


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