linux-kernel - Re: [PATCH 1/1] ptrace: Get tracer PID without reliance on the proc FS

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Message-ID: <CAHk-=wjhqn+B85OA8pfLhckUXSwLtJzFq5JPO2cNNzhPN__HJQ@mail.gmail.com>
Date: Wed, 11 Sep 2024 12:57:29 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Roman Kisel <romank@...ux.microsoft.com>, akpm@...ux-foundation.org, 
	apais@...rosoft.com, benhill@...rosoft.com, ebiederm@...ssion.com, 
	linux-kernel@...r.kernel.org, ssengar@...rosoft.com, sunilmut@...rosoft.com, 
	vdso@...bites.dev, workingjubilee@...il.com
Subject: Re: [PATCH 1/1] ptrace: Get tracer PID without reliance on the proc FS

On Wed, 11 Sept 2024 at 12:54, Oleg Nesterov <oleg@...hat.com> wrote:
>
>         - please try to make your changelog more convincing. And in particular,
>           please explain why !!current->ptrace is not enough and this feature
>           needs the tracer's pid.

Oleg, I realize you like the simpler patch that only has that
"!!current->ptrace", but my point is that even that simpler patch is
simply WRONG, WRONG, WRONG.

There is simply no valid situation where a "I have a tracer" is a good
thing to test for.

Whether it then gives just that "tracer exists" information, or the
pid of the tracer, or a proper pidfd that is actually reliable, is
then entirely immaterial. The whole feature fails at an earlier and
more fundamental point.

              Linus