Re: [PATCH 1/3] ptrace: ptrace_attach: check PF_KTHREAD + exit_state instead of ->mm

[Oleg Nesterov <oleg@redhat.com>]

On 05/05, Andrew Morton wrote:
>
> On Wed, 6 May 2009 00:47:22 +0200
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > - Add PF_KTHREAD check to prevent attaching to the kernel thread
> >   with a borrowed ->mm.
> >
> >   With or without this change we can race with daemonize() which
> >   can set PF_KTHREAD or clear ->mm after ptrace_attach() does the
> >   check, but this doesn't matter because reparent_to_kthreadd()
> >   does ptrace_unlink().
> >
> > - Kill "!task->mm" check. We don't really care about ->mm != NULL,
> >   and the task can call exit_mm() right after we drop task_lock().
> >   What we need is to make sure we can't attach after exit_notify(),
> >   check task->exit_state != 0 instead.
> >
>
> These patches make a mess of utrace-core.patch.  Do we really want to do that?

Aaaah. Sorry! forgot to clearify...

These patches depend on

	utrace-core-kill-exclude_xtrace-logic.patch

which hopefully can be folded into utrace-core.patch. In that case these
changes do not depend on utrace, and they can go ahead of utrace.

Is this acceptable for you ?

Oleg.