Re: [PATCH 1/1] ptrace: do_notify_parent_cldstop: fix the wrong ->nsproxy usage

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

Roland McGrath [roland@redhat.com] wrote:
| > Yes. Perhaps it would be nice to add a helper,
| 
| I agree.
| 
| > > sys_kill, do_tkill all look wrong to me.
| > 
| > They should be fine, note the
| > 
| > 	if (from_ancestor_ns)
| > 		q->info.si_pid = 0;
| > 
| > in __send_signal(). If we send the signal "down" to the sub-namespace,
| > si_pid == 0 is correct. And, unlike do_notify_parent/ptrace_notify/etc
| > kill/tkill can't send the signal "up".
| 
| Ah, right.  I knew there was something around this I was forgetting.

Setting si_pid to task_tgid_vnr(current); in places like do_tkill() is
slightly misleading bc, it can get modified later in send_signal().  We
can't set si_pid correctly in do_tkill() since we must first establish
pid-namespace relationship and that can mess up control flow.

Maybe a comment will help.