Re: [PATCH 1/2] seccomp: notify user trap about unused filter

From: Kees Cook
Date: Wed May 27 2020 - 18:38:06 EST

On Thu, May 28, 2020 at 12:05:32AM +0200, Christian Brauner wrote:
> The main question also is, is there precedence where the kernel just
> closes the file descriptor for userspace behind it's back? I'm not sure
> I've heard of this before. That's not how that works afaict; it's also
> not how we do pidfds. We don't just close the fd when the task
> associated with it goes away, we notify and then userspace can close.

But there's a mapping between pidfd and task struct that is separate
from task struct itself, yes? I.e. keeping a pidfd open doesn't pin
struct task in memory forever, right?

Kees Cook