Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: /proc/sys/user/max_time_namespaces?
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
        Andrey Vagin <avagin@openvz.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Containers <containers@lists.linux-foundation.org>,
        Adrian Reber <adrian@lisas.de>
References: <0fbcb669-33a8-9730-f7fa-639707532611@gmail.com>
From:   Dmitry Safonov <dima@arista.com>
Message-ID: <027226a2-f77c-0c1c-ee70-54a6c9194437@arista.com>
Date:   Mon, 6 Apr 2020 18:18:39 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <0fbcb669-33a8-9730-f7fa-639707532611@gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Michael,

On 4/3/20 1:21 PM, Michael Kerrisk (man-pages) wrote:
> Dmitry, Andrei
> 
> [Andrei, I mistyped your openvz address in an email of a few minutes
> ago ("[PATCH] ns: Fix time_for_children symlink"). You were CCed
> on your gmail address though.]
> 
> In the namespaces(7) manual page there is documentation for 
> these files:
> 
> $ ls -1 /proc/sys/user/*namespaces
> /proc/sys/user/max_cgroup_namespaces
> /proc/sys/user/max_ipc_namespaces
> /proc/sys/user/max_mnt_namespaces
> /proc/sys/user/max_net_namespaces
> /proc/sys/user/max_pid_namespaces
> /proc/sys/user/max_user_namespaces
> /proc/sys/user/max_uts_namespaces
> 
> These files allow one to limit on the number of namespaces
> of each type.
> 
> However, there is no /proc/sys/user/max_time_namespaces file.
> Was this deliberate, or an oversight?

Thanks a lot for noticing this!
Yes, it's an oversight and examining the code I can see that it's an
actual user-visible regression: max_inotify_instances controls time
namespaces limit.

I've just sent a patch to fix the issue, Cc'ing @stable:
https://lore.kernel.org/linux-api/20200406171342.128733-1-dima@arista.com/

Thanks again,
          Dmitry