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Subject: Re: [PATCH] add param that allows bootline control of hardened
 usercopy
To:     Chris von Recklinghausen <crecklin@redhat.com>,
        keescook@chromium.org, linux-kernel@vger.kernel.org,
        linux-mm@vger.kernel.org
References: <1529939300-27461-1-git-send-email-crecklin@redhat.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <5fe64898-d4df-1edd-37f0-5abbce6b2462@infradead.org>
Date:   Mon, 25 Jun 2018 09:09:11 -0700
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On 06/25/2018 08:08 AM, Chris von Recklinghausen wrote:
> Enabling HARDENED_USER_COPY causes measurable regressions in the
> networking performances, up to 8% under UDP flood.
> 
> A generic distro may want to enable HARDENED_USER_COPY in their default
> kernel config, but at the same time, such distro may want to be able to
> avoid the performance penalties in with the default configuration and
> enable the stricter check on a per-boot basis.
> 
> This change adds a config variable and a boot parameter to conditionally
> enable HARDENED_USER_COPY at boot time, and switch HUC to off if
> HUC_DEFAULT_OFF is set.
> 
> Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
> ---
>  .../admin-guide/kernel-parameters.rst         |  2 ++
>  .../admin-guide/kernel-parameters.txt         |  3 ++
>  include/linux/thread_info.h                   |  7 +++++
>  mm/usercopy.c                                 | 28 +++++++++++++++++++
>  security/Kconfig                              | 10 +++++++
>  5 files changed, 50 insertions(+)
> 

Hi,

> diff --git a/security/Kconfig b/security/Kconfig
> index c4302067a3ad..a6173897b85c 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -189,6 +189,16 @@ config HARDENED_USERCOPY_PAGESPAN
>  	  been removed. This config is intended to be used only while
>  	  trying to find such users.
>  
> +config HUC_DEFAULT_OFF
> +	bool "allow CONFIG_HARDENED_USERCOPY to be configured but disabled"
> +	depends on HARDENED_USERCOPY
> +	help
> +	  When CONFIG_HARDENED_USERCOPY is enabled, disable its
> +	  functionality unless it is enabled via at boot time

	                       it is enabled at boot time

> +	  via the "enable_hardened_usercopy" boot parameter. This allows
> +	  the functionality of hardened usercopy to be present but not
> +	  impact performance unless it is needed.
> +
>  config FORTIFY_SOURCE
>  	bool "Harden common str/mem functions against buffer overflows"
>  	depends on ARCH_HAS_FORTIFY_SOURCE
> 


-- 
~Randy