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

[Luca Boccassi]

On Fri, 4 Oct 2024 at 10:29, Christian Brauner <brauner@xxxxxxxxxx> wrote:
>
> On Wed, Oct 02, 2024 at 03:24:33PM GMT, luca.boccassi@xxxxxxxxx wrote:
> > +             info.pid = pid_nr_ns(pid, task_active_pid_ns(task));
>
> I think this is wrong what this should return is the pid of the process
> as seen from the caller's pid namespace. Otherwise you'll report
> meaningless pid numbers to the caller when the caller's pid namespace is
> outside of the pid namespace hierarchy of the process that pidfd refers
> to. This can easily happen when you receive pidfds via SCM_RIGHTS.

Thanks for the review, I applied the rest of the comments in v2 (I
think at least), but for this one I can't tell, how should I do it?
Naively I thought that task_active_pid_ns(task) would already fulfil
this requirement and resolve it using the correct pid namespace, is
that not the case? If not, what else should I do here?