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Date: Thu, 19 Jan 2017 11:11:18 +0000
From: Mark Rutland <mark.rutland@....com>
To: Laura Abbott <labbott@...hat.com>
Cc: Kees Cook <keescook@...omium.org>,
Jason Wessel <jason.wessel@...driver.com>,
Jonathan Corbet <corbet@....net>,
Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
"James E.J. Bottomley" <jejb@...isc-linux.org>,
Helge Deller <deller@....de>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
x86@...nel.org, Rob Herring <robh@...nel.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Jessica Yu <jeyu@...hat.com>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-parisc@...r.kernel.org, linux-s390@...r.kernel.org,
linux-pm@...r.kernel.org, kernel-hardening@...ts.openwall.com,
"AKASHI, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [PATCH 2/2] security: Change name of CONFIG_DEBUG_SET_MODULE_RONX
Hi,
On Wed, Jan 18, 2017 at 05:29:06PM -0800, Laura Abbott wrote:
>
> Despite the word 'debug' in CONFIG_DEBUG_SET_MODULE_RONX, this kernel
> option provides key security features that are to be expected on a
> modern system. Change the name to CONFIG_HARDENED_MODULE_MAPPINGS which
> more accurately describes what this option is intended to do.
This looks good; my naming comments from the DEBUG_RODATA also apply
here -- the proposed name is fine.
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 06fed56..2fe0e98 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -12,6 +12,7 @@ config ARM64
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_HAS_GIGANTIC_PAGE
> select ARCH_HAS_HARDENED_MAPPINGS
> + select ARCH_HAS_HARDENED_MODULE_MAPPINGS
> select ARCH_HAS_KCOV
> select ARCH_HAS_SG_CHAIN
> select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index a26d27f..1eebe1f 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -71,17 +71,6 @@ config DEBUG_WX
>
> If in doubt, say "Y".
>
> -config DEBUG_SET_MODULE_RONX
> - bool "Set loadable kernel module data as NX and text as RO"
> - depends on MODULES
> - default y
> - help
> - Is this is set, kernel module text and rodata will be made read-only.
> - This is to help catch accidental or malicious attempts to change the
> - kernel's executable code.
> -
> - If in doubt, say Y.
> -
> +config ARCH_HAS_HARDENED_MODULE_MAPPINGS
> + def_bool n
> +
> +config HARDENED_MODULE_MAPPINGS
> + bool "Mark module mappings with stricter permissions (RO/W^X)"
> + default y
> + depends on ARCH_HAS_HARDENED_MODULE_MAPPINGS
> + help
> + If this is set, module text and rodata memory will be made read-only,
> + and non-text memory will be made non-executable. This provides
> + protection against certain security vulnerabilities (e.g. modifying
> + code)
> +
> + Unless your system has known restrictions or performance issues, it
> + is recommended to say Y here.
> +
I was hoping that we'd make this mandatory, as we'd already done for
DEBUG_RODATA.
Takahiro-san did a bit of work towards that in commit 39290b389ea2654f
("module: extend 'rodata=off' boot cmdline parameter to module
mappings").
It would be good to know if there's any reason we can't do that.
Otherwise, this looks fine.
Thanks,
Mark.
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