linux-kernel - Re: [PATCH 2/2] kthread, cgroup: close race window where new kthreads can be migrated to non-root cgroups

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Message-ID: <20170316170321.GF15810@htj.duckdns.org>
Date:   Thu, 16 Mar 2017 13:03:21 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Chris Mason <clm@...com>,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org
Subject: Re: [PATCH 2/2] kthread, cgroup: close race window where new
 kthreads can be migrated to non-root cgroups

Hello,

On Thu, Mar 16, 2017 at 05:17:57PM +0100, Oleg Nesterov wrote:
> But this also means that __cgroup_procs_write() will always fail if
> this task is a kernel thread which was not created by kthread_create().
> 
> Currently you can use kernel_thread() (although you shouldn't) and it
> can be migrated, this won't work after your patch.

I see what you mean now.  The only users seem to be init/main.c and
kernel/kmod.c.  I'll see if there's a way we can do this only for
kthread_create() users.

Thanks.

-- 
tejun