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

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Date:	Tue, 26 May 2009 23:33:47 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] ptrace: do_notify_parent_cldstop: fix the wrong
	->nsproxy usage

On 05/26, Roland McGrath wrote:
>
> Acked-by: Roland McGrath <roland@...hat.com>
>
> Yes, all cases setting .si_pid should set it using the pid_ns of the
> recipient.  Numerous other cases look wrong too, though maybe Sukadev has
> outstanding patches for those already?  (It's been a while since we went
> around on this, and I am fuzzy on some of the details.)  ptrace_notify,
> ptrace_signal,

Yes. Perhaps it would be nice to add a helper,

	task_pid_xxx(struct task_struct child, struct task_struct *parent)
	{
		rcu_read_lock();
		ret = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
		rcu_read_unlock();

		return ret;
	}

ptrace_notify/ptrace_signal can race with untrace + clear ->nsproxy,
probably we don't care.

> 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".

Oleg.

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