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    SubjectRe: [RFC][PATCH-2.4] Prevent mounting on ".."
    On Sun, Jun 29, 2003 at 04:20:47PM +0200, Willy TARREAU wrote:
    > No, it works only with "..", and not with "." ! I don't know why, I believe
    > it's because the process is still attached to the old FS when mounting on ".".

    So? chdir around and you'll get to the covering directory.

    > > If attacker can mount of chroot - you've LOST. Already. End of story.
    >
    > To me, it seems this is the *only* remaining case in an *empty* read-only
    > directory. The fact is that the attacker needs at least a mount point to mount
    > something. Not providing him one is efficient, but here he can only exploit
    > "..".
    >
    > Please reconsider the question, Al, because I really think that with this, we
    > can get reliable jails for network daemons which don't need file access at all.

    Sigh... We _can't_ do that via chroot(). Please, stop fooling yourself -
    if attacker gets control over root process, the fight is over. In particular,
    attacker can chmod your read-only directory and/or remount the thing.
    -
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