Re: [PATCH 2/3] make kernel threads invisible to /sbin/init

[ebiederm@xmission.com (Eric W. Biederman)]

Oleg Nesterov <oleg@tv-sign.ru> writes:

> 1. rename reparent_to_init() to reparent_kthread() and export it
>
> 2. use init_pid_ns.child_reaper instead of child_reaper(current)
>
> 3. set ->exit_signal = -1, so init can't see us and we don't use
>    it to reap the task.
>
> 4. add reparent_kthread() to kthread() and stopmachine()
>

If the goal is to hide from /sbin/init.  We don't need to touch
kernel/kthread.c or 
kernel/stop_machine.c

Their parents are already kernel threads.

Yes. There is a startup issue for kernel/kthread.c I just about have
a patch I can stand that addresses that issue.

For the kernel thread they all inherit signals with SIGCHLD set to
SIG_IGN, so there is child auto reaping in that form.  Adding
the ->exit_signal = -1 would be a bonus but is not required.

I am a little concerned with removing the knowledge of who our
real parent is as that may compromise debugging.  The reason
why kernel threads are visible in the first place.

I do support reparenting kernel threads that call daemonize,
and the modifications to reparent_kthread here look reasonable.

Eric