linux-kernel - Re: High Resolution Timer DOS

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Message-ID: <Pine.LNX.4.64.0704282244130.25153@server.thyself>
Date:	Sat, 28 Apr 2007 22:45:03 +0000 (GMT)
From:	William Heimbigner <icxcnika@....tar.cc>
To:	Lee Revell <rlrevell@...-job.com>
cc:	tglx@...utronix.de, matthieu castet <castet.matthieu@...e.fr>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: High Resolution Timer DOS

On Sat, 28 Apr 2007, Lee Revell wrote:

> On 4/28/07, Thomas Gleixner <tglx@...utronix.de> 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).

Isn't that what /etc/security/limits.conf is for?
Just limit the CPU usage.

> Root and SCHED_FIFO tasks could be exempt from rate limiting, to avoid
> the need to introduce a new rlimit which would take years for
> userspace to catch up to.
>
> Lee

William Heimbigner
icxcnika@....tar.cc
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