linux-kernel - Re: Unkillable processes due to PTRACE

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Message-ID: <20161203191113.GA13417@amd>
Date:   Sat, 3 Dec 2016 20:11:13 +0100
From:   Pavel Machek <pavel@....cz>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        jan.kratochvil@...hat.com, palves@...hat.com,
        Roland McGrath <roland@...k.frob.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Unkillable processes due to PTRACE_TRACEME again

Hi!

You cc-ed me on initial mail, I replied, and you removed me from cc. Ouch.

On Sat 2016-12-03 16:55:49, Dmitry Vyukov wrote:
> On Fri, Dec 2, 2016 at 10:02 PM, Pavel Machek <pavel@....cz> wrote:
> > On Fri 2016-12-02 19:48:40, Dmitry Vyukov wrote:
> >> Hello,
> >>
> >> There was an issue discussed a year ago which leads to
> >> unkillalble/unwaitable zombie processes due to PTRACE_TRACEME:
> >> https://groups.google.com/d/msg/syzkaller/uGzwvhlCXAw/E-cfY2ejAgAJ
> >> and I though it has been fixed by "wait/ptrace: assume __WALL if the
> >> child is traced":
> >> https://groups.google.com/d/msg/syzkaller/caeB1ebZWAs/gcbvcM2HDAAJ
> >>
> >> I am not on 2caceb3294a78c389b462e7e236a4e744a53a474 (Dec 1). And see
> >
> > "Now on"?
> 
> Yes.
> 
> >> the same unwaitable zombie processes.
> >
> > Well.. I guess git bisect is one option...?
> 
> I've checked on:
> 
> commit 91c4e8ea8f05916df0c8a6f383508ac7c9e10dba
> Author: Oleg Nesterov <oleg@...hat.com>
> Date:   Mon May 23 16:23:53 2016 -0700
>     wait: allow sys_waitid() to accept __WNOTHREAD/__WCLONE/__WALL
> 
> and the program hangs the same way. So it seems that it was just never fixed.

Ouch #2. Oleg, any ideas?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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