linux-kernel - Re: [PATCH 1/5] refcount_t: A special purpose refcount type

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Date:   Fri, 3 Feb 2017 15:37:35 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Reshetova, Elena" <elena.reshetova@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Will Deacon <will.deacon@....com>,
        David Windsor <dwindsor@...il.com>,
        David Howells <dhowells@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 1/5] refcount_t: A special purpose refcount type

On Fri, Feb 3, 2017 at 5:25 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> Provide refcount_t, an atomic_t like primitive built just for
> refcounting.
>
> It provides saturation semantics such that overflow becomes impossible
> and thereby 'spurious' use-after-free is avoided.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  include/linux/refcount.h |  294 +++++++++++++++++++++++++++++++++++++++++++++++
>  lib/Kconfig.debug        |   13 ++
>  2 files changed, 307 insertions(+)
>
> --- /dev/null
> +++ b/include/linux/refcount.h
> @@ -0,0 +1,294 @@
> [...]
> +#if CONFIG_DEBUG_REFCOUNT

Oh, and I just hit this too, it should be "#ifdef" ... I didn't notice
until after I sent my improvement series. Whoops. :P Yay Friday.

-Kees

-- 
Kees Cook
Pixel Security