Re: [PATCH 1/3] fix setsid() for sub-namespace /sbin/init

[Oleg Nesterov <oleg@tv-sign.ru>]

On 11/26, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@tv-sign.ru> writes:
> 
> > sys_setsid() still deals with pid_t's from the global namespace. This means
> > that the "session > 1" check can't help for sub-namespace init, setsid() can't
> > succeed because copy_process(CLONE_NEWPID) populates PIDTYPE_PGID/SID links.
> 
> We can do even better.  We can remove the misguided code from
> copy_process(CLONE_NEWPID) that populates the PIDTYPE_PGID/SID links
> and generally does set setsid by hand,

Yes you are right. IIRC there was a patch from you, but I didn't follow the
discussion, sorry, so I don't know what was the verdict.

If we remove that "almost setsid" from copy_process(), we can remove the fat
comment and the "session != 1" chunk from setsid().

> and the code from kernel_init
> that call set_special_pid(), allowing us to remove the special case
> entirely.

This is different, perhaps we can keep this call. kernel_thread(kernel_init)
attaches /sbin/init to init_struct_pid. Nothing bad, and a "good" init should
do setsid() anyway. But who knows? Some special environment may expect that
getpgrp() != 0. Not that I really disagree on this issue though.

Oleg.