Re: [PATCH v2 2/2] pid: fix cad_pid use-after-free race

[Oleg Nesterov]

On 07/17, Cen Zhang (Microsoft) wrote:
>
>  int kill_cad_pid(int sig, int priv)
>  {
> -	return kill_pid(cad_pid, sig, priv);
> +	struct pid *pid;
> +	int ret;
> +
> +	rcu_read_lock();
> +	pid = get_pid(rcu_dereference(cad_pid));
> +	rcu_read_unlock();
> +
> +	ret = kill_pid(pid, sig, priv);
> +	put_pid(pid);

Hmm. Why do we need get/put_pid() ? I think that

	rcu_read_lock();
	ret = kill_pid(rcu_dereference(cad_pid), sig, priv);
	rcu_read_unlock();

	return ret;

should work just fine?

Oleg.