Re: [PATCH] kthread: fix use-after-free if kthread fork fails

[Oleg Nesterov]

On 05/05, Vegard Nossum wrote:
>
> On 05/05/17 18:44, Oleg Nesterov wrote:
> >
> >Can't we just move both
> >
> >	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
> >	/*
> >	 * Clear TID on mm_release()?
> >	 */
> >	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
> >
> >lines here?
>
> clone_flags is not available in dup_task_struct(), but we could move
> those lines higher in copy_process().

Yes, yes, this is what I meant.

> The newly attached patch has been tested and seems to work, if you
> prefer it.

Yes, please, this loos a bit better simply because we do not need to set it twice.

And I agree this needs cleanups. Even if we forget about this particular problem
and the usage of set_child_tid, we should add copy_misc() which should absorb a
lot of chaotic initializations from copy_process() imo.

Oleg.