From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v2 3/4] seccomp: add a way to get a listener fd from ptrace
Date: Thu, 17 May 2018 17:41:39 +0200
Message-ID: <20180517154139.GB8586@redhat.com>
References: <20180517151218.12850-1-tycho@tycho.ws>
	<20180517151218.12850-4-tycho@tycho.ws>
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To: Tycho Andersen <tycho-E0fblnxP3wo@public.gmane.org>
Cc: "Tobin C . Harding" <me-xzjC0nNlxno@public.gmane.org>, Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Akihiro Suda <suda.akihiro-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, "Eric W . Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>, Christian Brauner <christian.brauner-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>, Tyler Hicks <tyhicks-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
List-Id: containers.vger.kernel.org

again, I don't understand this code yet, but

On 05/17, Tycho Andersen wrote:
>
> +long seccomp_get_listener(struct task_struct *task,
> +			  unsigned long filter_off)
> +{
> +	struct seccomp_filter *filter;
> +	struct file *listener;
> +	int fd;
> +
> +	filter = get_nth_filter(task, filter_off);
> +	if (IS_ERR(filter))
> +		return PTR_ERR(filter);
> +
> +	fd = get_unused_fd_flags(O_RDWR);
> +	if (fd < 0) {
> +		__put_seccomp_filter(filter);
> +		return fd;
> +	}
> +
> +	listener = init_listener(task, task->seccomp.filter);
> +	if (IS_ERR(listener)) {
> +		put_unused_fd(fd);
> +		return PTR_ERR(listener);

__put_seccomp_filter() ?

and since init_listener() does __get_seccomp_filter() on sucess, it is needed
uncondtitionally?

Oleg.