linux-kernel - Re: [PATCH] pidfd: add ioctl to retrieve pid info

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Message-ID: <20241005112929.GA24386@redhat.com>
Date: Sat, 5 Oct 2024 13:29:29 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Luca Boccassi <luca.boccassi@...il.com>
Cc: Christian Brauner <brauner@...nel.org>,
	Jeff Layton <jlayton@...nel.org>,
	Josef Bacik <josef@...icpanda.com>, linux-kernel@...r.kernel.org,
	paul@...l-moore.com, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] pidfd: add ioctl to retrieve pid info

On 10/04, Luca Boccassi wrote:
>
> On Fri, 4 Oct 2024 at 20:30, Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > I guess Christian meant you should simply use
> >
> >                 info.pid = task_pid_vnr(task);
> >
> > task_pid_vnr(task) returns the task's pid in the caller's namespace.
>
> Ah I see, I didn't realize there was a difference, sent v3 with the
> suggested change just now, thanks.

I didn't get v3, I guess I wasn't cc'ed again.

So, just in case, let me add that task_pid_vnr(task) can return 0 if
this task exits after get_pid_task().

Perhaps this is fine, I do not know. But perhaps you should actually
use pid_vnr(pid).

Oleg.