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Date: Thu, 19 Jan 2017 11:43:25 +0000
From: Robin Murphy <robin.murphy@....com>
To: Laura Abbott <labbott@...hat.com>
Cc: Kees Cook <keescook@...omium.org>, Mark Rutland <mark.rutland@....com>,
linux-doc@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
"James E.J. Bottomley" <jejb@...isc-linux.org>, Pavel Machek <pavel@....cz>,
"H. Peter Anvin" <hpa@...or.com>, kernel-hardening@...ts.openwall.com,
Rob Herring <robh@...nel.org>, Jessica Yu <jeyu@...hat.com>,
Jonathan Corbet <corbet@....net>, Helge Deller <deller@....de>,
x86@...nel.org, Russell King <linux@...linux.org.uk>,
Ingo Molnar <mingo@...hat.com>, Len Brown <len.brown@...el.com>,
linux-s390@...r.kernel.org, Will Deacon <will.deacon@....com>,
Thomas Gleixner <tglx@...utronix.de>, linux-arm-kernel@...ts.infradead.org,
linux-parisc@...r.kernel.org, linux-pm@...r.kernel.org,
"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-kernel@...r.kernel.org,
Jason Wessel <jason.wessel@...driver.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 2/2] security: Change name of CONFIG_DEBUG_SET_MODULE_RONX
Hi Laura,
On 19/01/17 01:29, 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.
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
[...]
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 09aff28..ef852e4 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -8,6 +8,7 @@ config ARM
> select ARCH_HAVE_CUSTOM_GPIO_H
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_HAS_HARDENED_MAPPINGS if MMU && !XIP_KERNEL
> + select ARCH_HAS_HARDENED_MODULE_MAPPINGS if MMU
> select ARCH_MIGHT_HAVE_PC_PARPORT
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_USE_BUILTIN_BSWAP
> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
> index d83f7c3..426d271 100644
> --- a/arch/arm/Kconfig.debug
> +++ b/arch/arm/Kconfig.debug
> @@ -1738,17 +1738,6 @@ config PID_IN_CONTEXTIDR
> additional instructions during context switch. Say Y here only if you
> are planning to use hardware trace tools with this kernel.
>
> -config DEBUG_SET_MODULE_RONX
> - bool "Set loadable kernel module data as NX and text as RO"
> - depends on MODULES && MMU
> - ---help---
> - This option helps catch unintended modifications to loadable
> - kernel module's text and read-only data. It also prevents execution
> - of module data. Such protection may interfere with run-time code
> - patching and dynamic kernel tracing - and they might also protect
> - against certain classes of kernel exploits.
> - If in doubt, say "N".
> -
> source "drivers/hwtracing/coresight/Kconfig"
>
> endmenu
[...]
> --- 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 DEBUG_ALIGN_RODATA
> depends on ARCH_HAS_HARDENED_MAPPINGS
> bool "Align linker sections up to SECTION_SIZE"
[...]
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -69,6 +69,7 @@ config S390
> 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_UBSAN_SANITIZE_ALL
> diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
> index 26c5d5be..57f8ea9 100644
> --- a/arch/s390/Kconfig.debug
> +++ b/arch/s390/Kconfig.debug
> @@ -17,7 +17,4 @@ config S390_PTDUMP
> kernel.
> If in doubt, say "N"
>
> -config DEBUG_SET_MODULE_RONX
> - def_bool y
> - depends on MODULES
> endmenu
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 9d80cd8..38ce850 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -51,6 +51,7 @@ config X86
> select ARCH_HAS_FAST_MULTIPLIER
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_HAS_HARDENED_MAPPINGS
> + select ARCH_HAS_HARDENED_MODULE_MAPPINGS
> select ARCH_HAS_KCOV if X86_64
> select ARCH_HAS_MMIO_FLUSH
> select ARCH_HAS_PMEM_API if X86_64
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index 67eec55..69cdd0b 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -109,17 +109,6 @@ 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
> - ---help---
> - This option helps catch unintended modifications to loadable
> - kernel module's text and read-only data. It also prevents execution
> - of module data. Such protection may interfere with run-time code
> - patching and dynamic kernel tracing - and they might also protect
> - against certain classes of kernel exploits.
> - If in doubt, say "N".
> -
> config DEBUG_NX_TEST
> tristate "Testcase for the NX non-executable stack feature"
> depends on DEBUG_KERNEL && m
[...]
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -174,6 +174,22 @@ config HARDENED_PAGE_MAPPINGS
> Unless your system has known restrictions or performance issues, it
> is recommended to say Y here.
>
> +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
It would seem that this ends up losing the previous dependency on
MODULES - is that intentional?
Robin.
> + 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.
> +
> source security/selinux/Kconfig
> source security/smack/Kconfig
> source security/tomoyo/Kconfig
>
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