linux-kernel - Re: [PATCH] kernel/time: Add max_time

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Message-ID: <20200407033148.GB494464@gmail.com>
Date:   Mon, 6 Apr 2020 20:31:48 -0700
From:   Andrei Vagin <avagin@...il.com>
To:     Dmitry Safonov via Containers 
        <containers@...ts.linux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrey Vagin <avagin@...nvz.org>,
        Dmitry Safonov <dima@...sta.com>,
        Linux API <linux-api@...r.kernel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>, stable@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Adrian Reber <adrian@...as.de>
Subject: Re: [PATCH] kernel/time: Add max_time_namespaces ucount

On Mon, Apr 06, 2020 at 06:13:42PM +0100, Dmitry Safonov via Containers wrote:
> Introduce missing time namespaces limit per-userns.
> Michael noticed that userns limit for number of time namespaces is
> missing.
> 
> Furthermore, time namespace introduced UCOUNT_TIME_NAMESPACES, but
> didn't introduce an array member in user_table[]. It would make array's
> initialisation OOB write, but by luck the user_table array has
> an excessive empty member (all accesses to the array are limited with
> UCOUNT_COUNTS - so it silently reuses the last free member.
> 
> Fixes user-visible regression: max_inotify_instances by reason of the
> missing UCOUNT_ENTRY() has limited max number of namespaces instead of
> the number of inotify instances.
> 
> Fixes: 769071ac9f20 ("ns: Introduce Time Namespace")
> Cc: Adrian Reber <adrian@...as.de>
> Cc: Andrey Vagin <avagin@...nvz.org>
> Cc: Christian Brauner <christian.brauner@...ntu.com>
> Cc: Eric W. Biederman <ebiederm@...ssion.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vincenzo Frascino <vincenzo.frascino@....com>
> Cc: Containers <containers@...ts.linux-foundation.org>
> Cc: Linux API <linux-api@...r.kernel.org>
> Cc: stable@...nel.org # v5.6+
> Reported-by: Michael Kerrisk (man-pages) <mtk.manpages@...il.com>

Acked-by: Andrei Vagin <avagin@...il.com>

> Signed-off-by: Dmitry Safonov <dima@...sta.com>