linux-kernel - Re: [PATCH][DEBUG] x86/refcount: split up refcount saturation handling

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Date:   Sat, 2 Sep 2017 12:35:00 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Mike Galbraith <efault@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][DEBUG] x86/refcount: split up refcount saturation
 handling


* Kees Cook <keescook@...omium.org> wrote:

> In support of debugging the problems Mike Galbraith has seen with
> x86-refcount vs gcc vs network refcounts...
> 
> This minimizes the differences between unchecked-refcount and x86-refcount
> by changing the refcount_dec() failure case to not saturate. The reporting
> of negative values is reduced to pr_warn from WARN to avoid spamming dmesg
> (which may impact race conditions). Ratelimiting is disabled just to be
> sure no reports are being dropped.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  arch/x86/mm/extable.c | 51 ++++++++++++++++++++++++++++++++++-----------------
>  kernel/panic.c        |  2 +-
>  2 files changed, 35 insertions(+), 18 deletions(-)

If this patch is still useful then please include it in your next refcount series. 
Better debuggability is always welcome.

Thanks,

	Ingo