linux-kernel - Re: [PATCH 7/7] ptrace: s/tracehook_tracer_task()/ptrace

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Date:	Mon, 20 Jun 2011 22:16:03 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, hch@...radead.org,
	John Johansen <john.johansen@...onical.com>,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH 7/7] ptrace: s/tracehook_tracer_task()/ptrace_parent()/

On 06/17, Tejun Heo wrote:
>
> tracehook.h is on the way out.  Rename tracehook_tracer_task() to
> ptrace_parent() and move it from tracehook.h to ptrace.h.

I am a bit surpised you decided to keep this helper. Can't we simply
kill it?

OK, we will see. I guess this change is mostly needed to remove yet
another function from tracehook.h.

> @@ -216,7 +216,7 @@ static struct mm_struct *__check_mem_permission(struct task_struct *task)
>  	if (task_is_stopped_or_traced(task)) {
>  		int match;
>  		rcu_read_lock();
> -		match = (tracehook_tracer_task(task) == current);
> +		match = (ptrace_parent(task) == current);
>  		rcu_read_unlock();
>  		if (match && ptrace_may_access(task, PTRACE_MODE_ATTACH))

All we need

	if (task_is_traced(task) && task->parent == current) {
		if (ptrace_may_access()
			return mm;
	}

Of course I do not blame this patch, my only point is that this helper
only adds more confusion imho.




> @@ -67,7 +67,7 @@ static int may_change_ptraced_domain(struct task_struct *task,
>  	int error = 0;
>
>  	rcu_read_lock();
> -	tracer = tracehook_tracer_task(task);
> +	tracer = ptrace_parent(task);
>  	if (tracer) {
>  		/* released below */
>  		cred = get_task_cred(tracer);

Hmm. And then this task_struct is used after we dropped rcu_read_lock().

John, is this correct?

Oleg.

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