linux-kernel - Re: [PATCH v2 1/4] seccomp: add a return code to trap to userspace

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Message-ID: <20180517153323.GA8586@redhat.com>
Date:   Thu, 17 May 2018 17:33:24 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Tyler Hicks <tyhicks@...onical.com>,
        Akihiro Suda <suda.akihiro@....ntt.co.jp>,
        "Tobin C . Harding" <me@...in.cc>
Subject: Re: [PATCH v2 1/4] seccomp: add a return code to trap to userspace

I didn't read this series yet, and I don't even understand what are you
trying to do, just one question...

On 05/17, Tycho Andersen wrote:
>
> +static struct file *init_listener(struct task_struct *task,
> +				  struct seccomp_filter *filter)
> +{
> +	struct file *ret = ERR_PTR(-EBUSY);
> +	struct seccomp_filter *cur;
> +	bool have_listener = false;
> +
> +	for (cur = task->seccomp.filter; cur; cur = cur->prev) {
> +		mutex_lock(&cur->notify_lock);

Did you test this patch with CONFIG_LOCKDEP ?

>From lockdep pov this loop tries to take the same lock twice or more, it shoul
complain.

Oleg.