linux-kernel - Re: [RESEND PATCH v6 0/5] proc: subset=pid: Relax check of mount visibility

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Message-ID: <20251213050639.735940-1-danilklishch@gmail.com>
Date: Sat, 13 Dec 2025 00:06:38 -0500
From: Dan Klishch <danilklishch@...il.com>
To: legion@...nel.org,
	linux-kernel@...r.kernel.org
Cc: ebiederm@...ssion.com,
	viro@...iv.linux.org.uk,
	keescook@...omium.org,
	containers@...ts.linux-foundation.org,
	linux-fsdevel@...r.kernel.org,
	Dan Klishch <danilklishch@...il.com>
Subject: Re: [RESEND PATCH v6 0/5] proc: subset=pid: Relax check of mount visibility

Hello Alexey,

Would it be possible to revive this patch series?

I wanted to add an additional downstream use case that would benefit
from this work. In particular, I am trying to run the sandbox
sunwalker-box [1] without root privileges and/or inside a container.

The sandbox aims to prevent cross-run communication via side channels,
and PID allocation is one such channel. Therefore, it creates a new PID
namespace and mounts the corresponding procfs instance inside of the
sandbox. This currently works without a real root when procfs is fully
accessible, but obviously fails otherwise.

Thanks,
Dan Klishch

[1] https://github.com/purplesyringa/sunwalker-box/