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

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Message-ID: <201907290949.D08EC0379C@keescook>
Date:   Mon, 29 Jul 2019 09:51:04 -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 06:55:47PM +0200, Jann Horn wrote:
> (Accurate) statistics counters need RMW ops, don't need memory
> ordering, usually can't be locked against writes, and may not care
> about wrapping.
> This thing doesn't need RMW ops, does need memory ordering, can be
> locked against writes, and definitely shouldn't wrap.
> 
> I agree that there are a bunch of statistics counters in the kernel,
> and it's not necessarily a bad idea to use a separate type for them;
> but this is not a statistics counter.

Right, yes, I didn't meant to suggest it should be. I was just bringing
up the "counter type" idea again, since it was on my mind here
originally.

-- 
Kees Cook