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Date:   Tue, 15 Feb 2022 12:37:48 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Shuah Khan <skhan@linuxfoundation.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        linux-kernel@vger.kernel.org, Alexey Gladkov <legion@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Solar Designer <solar@openwall.com>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>,
        Linux Containers <containers@lists.linux-foundation.org>
Subject: Re: [PATCH 0/8] ucounts: RLIMIT_NPROC fixes
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On Fri, Feb 11, 2022 at 11:22:13AM -0700, Shuah Khan <skhan@linuxfoundation.org> wrote:
> Do we need updates to selftests - Michal's patch series included changes to
> selftests/exec

In my understanding the original rlimits-per-userns.c covers an invalid
use case -- clone(0);setuid();unshare(CLONE_NEWUSER) -- where the
created user_ns is owned by unprivileged user and the global
RLIMIT_NPROC cannot be breached.

My patched variant retains this use-case (should fail) and adds
clone(CLONE_NEWUSER);setuid() [1] variant which should be the valid
use-case for per-user per-user-ns RLIMIT_NPROC.

Michal

[1] In this situation theoretically equivalent to clone(0);unshare(CLONE_NEWUSER);setuid().