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Date: Thu, 21 Sep 2017 18:45:48 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>, hw.likun@huawei.com
Subject: Re: [PATCH] arm64: Always use REFCOUNT_FULL
Message-ID: <20170921174548.GM32076@ZenIV.linux.org.uk>
References: <20170920204959.GA79741@beast>
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On Wed, Sep 20, 2017 at 01:49:59PM -0700, Kees Cook wrote:
> As discussed at the Linux Security Summit, arm64 prefers to use
> REFCOUNT_FULL by default. This enables it for the architecture.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: hw.likun@huawei.com
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 0df64a6a56d4..9fe7a7f4c94c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -119,6 +119,7 @@ config ARM64
>  	select PCI_ECAM if ACPI
>  	select POWER_RESET
>  	select POWER_SUPPLY
> +	select REFCOUNT_FULL

Umm...  That does a bit more than "on by default", unless I'm
misreading it.  More like "on, and you can't opt out"...