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From: Oleg Nesterov <oleg@redhat.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Roland McGrath <roland@hack.frob.com>,
	syzkaller@googlegroups.com, Kostya Serebryany <kcc@google.com>,
	Alexander Potapenko <glider@google.com>,
	Robert Swiecki <swiecki@google.com>,
	Kees Cook <keescook@google.com>, Julien Tinnes <jln@google.com>,
	Eric Dumazet <edumazet@google.com>
Subject: Re: Unkillable processes due to PTRACE_TRACEME
Date: Fri, 4 Dec 2015 20:02:50 +0100	[thread overview]
Message-ID: <20151204190244.GA16199@redhat.com> (raw)
In-Reply-To: <20151203205613.GC14427@amd>

Hi Pavel,

On 12/03, Pavel Machek wrote:
>
> > You can't. This is one of historical oddities. You need to reap the
> > traced sub-thread first. And PTRACE_DETACH doesn't work.
>
> If kill -9 does not take out the process,

Just in case, "kill -9" can't help because the task is already killed and
zombie. The problem is that /sbin/init can't reap it without __WALL unless
we change the kernel.

> surely that sounds like a
> security problem?
>
> I know ptrace is old and tricky and ugly, but ....?

Yes this should be fixed. I'll resend the patches next week, I am a bit busy
now.

And, Dmitry, I didn't forget about another problem you reported ;) I'll try
to redo/resend the fixes for WARN_ON() in in task_participate_group_stop()
as well.

Oleg.


      reply	other threads:[~2015-12-04 19:02 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-19 17:53 Unkillable processes due to PTRACE_TRACEME Dmitry Vyukov
2015-10-19 19:49 ` Oleg Nesterov
2015-10-19 20:17   ` Dmitry Vyukov
2015-10-20  8:34     ` Dmitry Vyukov
2015-10-20  8:39       ` Dmitry Vyukov
2015-10-20 10:55         ` Oleg Nesterov
2015-12-03 20:56           ` Pavel Machek
2015-12-04 19:02             ` Oleg Nesterov [this message]

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