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

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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




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