linux-kernel - Re: Unkillable processes due to PTRACE

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Date:   Sat, 3 Dec 2016 16:55:49 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzkaller <syzkaller@...glegroups.com>
Cc:     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

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.