linux-kernel - Re: PID namespace init releases its file locks before its children die

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Message-ID: <20251007-pause-raunen-b960e62d000c@brauner>
Date: Tue, 7 Oct 2025 14:02:59 +0200
From: Christian Brauner <brauner@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Demi Marie Obenour <demiobenour@...il.com>, 
	Mateusz Guzik <mjguzik@...il.com>, Linux kernel mailing list <linux-kernel@...r.kernel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: PID namespace init releases its file locks before its children
 die

On Fri, Oct 03, 2025 at 02:38:28PM +0200, Oleg Nesterov wrote:
> Add CCs.
> 
> I can't really help, just my 2 cents...
> 
> I don't think we can change do_exit() to call exit_files() after
> exit_notify().
> 
> At first glance, technically it is possible to change do_exit() so
> that the exiting reaper does zap_pid_ns_processes() earlier... But
> even if this is possible, I think that this complication needs more
> justification.

I agree. Relying on side-effect of file locks being released isn't exactly
a great idea. I'm certainly don't want to give any guarantee there. It's
doable with cgroups which is the correct solution for this imho.