linux-kernel - Re: [PATCH] selinux: convert struct sidtab count to refcount

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Message-ID: <201907240852.6D10622B2@keescook>
Date:   Wed, 24 Jul 2019 08:54:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Ondrej Mosnacek <omosnace@...hat.com>,
        NitinGote <nitin.r.gote@...el.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        SElinux list <selinux@...r.kernel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selinux: convert struct sidtab count to refcount_t

On Wed, Jul 24, 2019 at 04:28:31PM +0200, Jann Horn wrote:
> On Wed, Jul 24, 2019 at 12:17 AM Kees Cook <keescook@...omium.org> wrote:
> > Perhaps we need a "statistics" counter type for these kinds of counters?
> > "counter_t"? I bet there are a lot of atomic_t uses that are just trying
> > to be counters. (likely most of atomic_t that isn't now refcount_t ...)
> 
> This isn't a statistics counter though; this thing needs ordered
> memory accesses, which you wouldn't need for statistics.

Okay, it'd be a "very accurate" counter type? It _could_ be used for
statistics. I guess what I mean is that there are a lot of places using
atomic_t just for upward counting that don't care about wrapping, etc.

-- 
Kees Cook