linux-kernel - Re: perf_event_open+clone = unkillable process

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Message-ID: <alpine.DEB.2.21.1902041025050.8200@nanos.tec.linutronix.de>
Date:   Mon, 4 Feb 2019 10:27:23 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dmitry Vyukov <dvyukov@...gle.com>
cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        jolsa@...hat.com, Namhyung Kim <namhyung@...nel.org>,
        luca abeni <luca.abeni@...tannapisa.it>,
        syzkaller <syzkaller@...glegroups.com>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: perf_event_open+clone = unkillable process

On Fri, 1 Feb 2019, Dmitry Vyukov wrote:

> On Fri, Feb 1, 2019 at 5:48 PM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> >
> > Hello,
> >
> > The following program creates an unkillable process that eats CPU.
> > /proc/pid/stack is empty, I am not sure what other info I can provide.
> >
> > Tested is on upstream commit 4aa9fc2a435abe95a1e8d7f8c7b3d6356514b37a.
> > Config is attached.
> 
> Looking through other reproducers that create unkillable processes, I
> think I found a much simpler reproducer (below). It's single threaded
> and just setups SIGBUS handler and does timer_create+timer_settime to
> send repeated SIGBUS. The resulting process can't be killed with
> SIGKILL.
> +Thomas for timers.

+Oleg, Eric

That's odd. With some tracing I can see that SIGKILL is generated and
queued, but its not delivered by some weird reason. I'm traveling in the
next days, so I won't be able to do much about it. Will look later this
week.

Thanks,

	tglx