[PATCH] signal: Avoid corrupting si_pid and si_uid in do_notify_parent

[Oleg Nesterov]

On 04/20, Eric W. Biederman wrote:
>
> The immediate problem is as Christof noticed that "pid_alive(current) == false".

this is slightly offtopic, but we can probably remove this "pid_alive" check,
pid_nr_ns() checks pid != NULL anyway.

> Inspecting the code it appears this problem has existed since the pid
> namespace support started handling this case

Agreed...

> @@ -1993,8 +1993,12 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
>  		if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
>  			sig = 0;
>  	}
> +	/*
> +	 * Bypass send_signal as the si_pid and si_uid values have
> +	 * been generated in the parent's namespaces.
> +	 */
>  	if (valid_signal(sig) && sig)
> -		__group_send_sig_info(sig, &info, tsk->parent);
> +		__send_signal(sig, &info, tsk->parent, PIDTYPE_TGID, false);

Acked-by: Oleg Nesterov <oleg at redhat.com>