linux-kernel - Re: clock_nanosleep() task

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Message-ID: <20130205103455.GB18313@redhat.com>
Date:	Tue, 5 Feb 2013 11:34:56 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Tommi Rantala <tt.rantala@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	John Stultz <john.stultz@...aro.org>
Subject: Re: clock_nanosleep() task_struct leak

On Mon, Feb 04, 2013 at 08:32:23PM +0100, Oleg Nesterov wrote:
> On 02/01, Thomas Gleixner wrote:
> >
> > B1;2601;0cOn Fri, 1 Feb 2013, Tommi Rantala wrote:
> >
> > > Hello,
> > >
> > > Trinity discovered a task_struct leak with clock_nanosleep(), reproducible with:
> > >
> > > -----8<-----8<-----8<-----
> > > #include <time.h>
> > >
> > > static const struct timespec req;
> > >
> > > int main(void) {
> > >         return clock_nanosleep(CLOCK_PROCESS_CPUTIME_ID,
> > >                         TIMER_ABSTIME, &req, NULL);
> > > }
> > > -----8<-----8<-----8<-----
> 
> posix_cpu_timer_create()->get_task_struct() I guess...
> 
> Cough. I am not sure I ever understood this code, but now it certainly
> looks as if I never saw it before.

Looks on do_cpu_nanosleep() we call posix_cpu_timer_create(), but we do
not call posix_cpu_timer_del() at the end. Fix will not be super simple,
since we need to care about error cases. I can cook a patch if nobody
else want to do this.

Stanislaw
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