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    SubjectRe: [GIT PULL] Namespace file descriptors for 2.6.40
    Quoting C Anthony Risinger (anthony@xtfx.me):
    > On Mon, May 23, 2011 at 4:05 PM, Eric W. Biederman
    > <ebiederm@xmission.com> wrote:
    > >
    > > This tree adds the files /proc/<pid>/ns/net, /proc/<pid>/ns/ipc,
    > > /proc/<pid>/ns/uts that can be opened to refer to the namespaces of a
    > > process at the time those files are opened, and can be bind mounted to
    > > keep the specified namespace alive without a process.
    > >
    > > This tree adds the setns system call that can be used to change the
    > > specified namespace of a process to the namespace specified by a system
    > > call.
    >
    > i just have a quick question regarding these, apologies if wrong place
    > to respond -- i trimmed to lists only.
    >
    > if i understand correctly, mount namespaces (for example), allow one
    > to build such constructs as "private /tmp" and similar that even
    > `root` cannot access ... and there are many reasons `root` does not
    > deserve to completely know/interact with user processes (FUSE makes a
    > good example ... just because i [user] have SSH access to a machine,
    > why should `root`?)
    >
    > would these /proc additions break such guarantees? IOW, would it now
    > become possible for `root` to inject stuff into my private namespaces,
    > and/or has these guarantees never existed and i am mistaken? is there
    > any kind of ACL mechanism that endows the origin process (or similar)
    > with the ability to dictate who can hold and/or interact with these
    > references?

    If for instance you have a file open in your private /tmp, then root
    in another mounts ns can open the file through /proc/$$/fd/N anyway.
    If it's a directory, he can now traverse the whole fs.

    -serge


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