[PATCH 6/9] signal: Always call do_notify_parent_cldstop with siglock held

[Oleg Nesterov]

On 04/27, Eric W. Biederman wrote:
>
> The ptrace parental relationship definitely has the potential to be a
> graph with cycles.  Which as you point out is not fine.
>
> The result is very nice and I don't want to give it up.  I suspect
> something ptrace cycles are always a problem and can simply be
> forbidden.

OK, please consider another case.

We have a parent P and its child C. C traces P.

This is not that unusual, I don't think we can forbid this case.

P reports an event and calls do_notify_parent_cldstop().

C receives SIGSTOP and calls do_notify_parent_cldstop() too.

Oleg.