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Date:   Thu, 10 Jan 2019 15:37:47 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Andrei Vagin <avagin@gmail.com>
Cc:     Oleg Nesterov <oleg@redhat.com>, linux-kernel@vger.kernel.org,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH v2] kernel: release ptraced tasks before
 zap_pid_ns_processes
Message-Id: <20190110153747.75787a99b380f415ee38d145@linux-foundation.org>
In-Reply-To: <20190110175200.12442-1-avagin@gmail.com>
References: <20190110175200.12442-1-avagin@gmail.com>
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On Thu, 10 Jan 2019 09:52:00 -0800 Andrei Vagin <avagin@gmail.com> wrote:

> Currently, exit_ptrace() adds all ptraced tasks in a dead list, than
> zap_pid_ns_processes() waits all tasks in a current pidns, and only
> then tasks from the dead list are released.
> 
> zap_pid_ns_processes() can stuck on waiting tasks from the dead list. In
> this case, we will have one unkillable process with one or more dead
> children.
> 
> Thanks to Oleg for the advice to release tasks in find_child_reaper().
> 
> Fixes: 7c8bd2322c7f ("exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()")
> 
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Andrei Vagin <avagin@gmail.com>

Does this warrant a -stable backport?  7c8bd2322c7f was 4+ years ago...