Re: [PATCH 2/2] security: Change name of CONFIG_DEBUG_SET_MODULE_RONX

[Laura Abbott]

On 01/19/2017 12:43 PM, Robin Murphy wrote:
> 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@xxxxxxxxxx>
> > ---
>
> [...]
>
> > 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.

(Apologies, my SMTP was set up incorrectly so this didn't actually
get sent out when I thought it did)

No, good catch. I missed re-adding that when doing the refactoring.

Thanks,
Laura

> >