From: Ingo Molnar <mingo@elte.hu>
To: Lee Revell <rlrevell@joe-job.com>
Cc: tglx@linutronix.de, matthieu castet <castet.matthieu@free.fr>,
Linux Kernel list <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: High Resolution Timer DOS
Date: Sun, 29 Apr 2007 09:17:43 +0200 [thread overview]
Message-ID: <20070429071743.GA4532@elte.hu> (raw)
In-Reply-To: <75b66ecd0704281537s54134967ybc3ddef0b87b6bf5@mail.gmail.com>
* Lee Revell <rlrevell@joe-job.com> wrote:
> > Well, it is not really a DoS. The rescheduling of the process is
> > limited by the scheduler and the available CPU time (depending on
> > the number of runnable tasks in the system).
>
> Shouldn't an unprivileged process be rate limited somehow to avoid
> flooding the machine with interrupts? We restrict nonroot users from
> setting the RTC interrupt rate higher than 64Hz for a similar reason
> (granted, this limit dates back to the 486 days and should probably be
> increased to 1024 Hz).
No. An interrupt in this case is really just 'CPU time used up', and an
unprivileged process can take up as much CPU time as the scheduler
allows. So it's _not_ a DoS, and neither is any other unprivileged
infinit loop (or high-rate context-switching task) a DoS.
Ingo
next prev parent reply other threads:[~2007-04-29 7:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-28 21:53 High Resolution Timer DOS matthieu castet
2007-04-28 22:13 ` Thomas Gleixner
2007-04-28 22:37 ` Lee Revell
2007-04-28 22:45 ` William Heimbigner
2007-04-29 7:17 ` Ingo Molnar [this message]
2007-04-29 16:08 ` matthieu castet
2007-04-29 16:42 ` Ingo Molnar
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