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    SubjectRe: /proc/sys/kernel/pid_max issues

    * Albert Cahalan <albert@users.sf.net> wrote:

    > > > I'd much prefer LRU allocation. There are
    > > > lots of system calls that take PID values.
    > > > All such calls are hazardous. They're pretty
    > > > much broken by design.
    > >
    > > this is a pretty sweeping assertion. Would you
    > > care to mention a few examples of such hazards?
    >
    > kill(12345,9)
    > setpriority(PRIO_PROCESS,12345,-20)
    > sched_setscheduler(12345, SCHED_FIFO, &sp)
    >
    > Prior to the call being handled, the process may
    > die and be replaced. Some random innocent process,
    > or a not-so-innocent one, will get acted upon by
    > mistake. This is broken and dangerous.

    easy to fix: SIGSTOP the task, check it's really
    the one you want and then do the setpriority /
    setscheduler call and SIGCONT it. Any privileged
    code that is about to spread some of its privileges
    via asynchronous system-calls need to be careful.

    Ingo
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