Re: /proc/sys/kernel/pid_max issues

From: Pavel Machek (pavel_at_ucw.cz)
Date: 09/18/04

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    Date:	Sat, 18 Sep 2004 20:32:50 +0200
To: Ingo Molnar <mingo@elte.hu>

    Hi!

    > > > > 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.

    What if OOM killer decides it wants that memory in between? Attacker
    could probably help it...
                                                                    Pavel 

    -- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
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  • Next message: Jon Smirl: "Design for setting video modes, ownership of sysfs attributes"