linux-kernel - Re: /proc/sys/user/max_time

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Date:   Mon, 6 Apr 2020 18:18:39 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        Andrey Vagin <avagin@...nvz.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Containers <containers@...ts.linux-foundation.org>,
        Adrian Reber <adrian@...as.de>
Subject: Re: /proc/sys/user/max_time_namespaces?

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