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    SubjectRe: Why wrapping PIDs is evil [was 32bit]
    On Sun, 16 Jan 2000, Pavel Machek wrote:

    > > > Sorry, alan. No. Unix is broken with this part.
    > >
    > > When you run as root, you run risks and have to be careful.
    >
    > No. You can't be carefull. Users have full chance to get you in this case.

    Then don't run as root if you're that concerned.

    > > thing about Unix is that it wraps pids and does _not_ pick random pids. You shouldn't
    > > get around to the same pid for at least a reasonable amount of time, unless someone
    > > is spawning processes _very_ fast.
    >
    > But someone probably _is_ spawning processes very fast if they want to
    > screw you.

    There are a number of generally more useful (to the 'evil' one) things that
    can be done. In any case, perhaps coming up w/ a patch to allow for a 64bit PID,
    and fixing up everything to use it, while not introducing any new security holes,
    and fixing every program in existance that uses a pid will do what you want, but
    I don't see much of a payoff for that much work.

    > > > But that's wrong. Pavel may have seen you are going to kill his emacs
    > > > and may have wrapped pids, killed his emacs himself, and you are now
    > > > killing _your_ netscape you've just ran.
    > >
    > > Erm, too bad that's exactly what _doesn't_ happen under Unix. Your netscape
    > > you just started will get a new pid, after the latest one taken. No matter if that
    > > process died or not.
    >
    > I forgot to mention: of course _pavel_ is evil and created/killed just
    > enough processes for PIDs to wrap in bad way.

    If _pavel_ is evil, and got lucky enough to manage this, chances are
    _pavel_ won't be around on that box much longer.

    Stephen


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