[PATCHv3 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common

From: Laura Abbott
Date: Mon Feb 06 2017 - 19:32:24 EST

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There are multiple architectures that support CONFIG_DEBUG_RODATA and
CONFIG_SET_MODULE_RONX. These options also now have the ability to be
turned off at runtime. Move these to an architecture independent
location and make these options def_bool y for almost all of those
arches.

Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
---
v3: Make these configs selectable for arm. Include some documentation about
how the setup of the optional Kconfigs work as well. Stop spelling 'kenrel'
in prompt text.
---
Documentation/security/self-protection.txt | 6 ++++++
arch/Kconfig | 34 ++++++++++++++++++++++++++++++
arch/arm/Kconfig | 4 ++++
arch/arm/Kconfig.debug | 11 ----------
arch/arm/mm/Kconfig | 12 -----------
arch/arm64/Kconfig | 5 ++---
arch/arm64/Kconfig.debug | 11 ----------
arch/parisc/Kconfig | 1 +
arch/parisc/Kconfig.debug | 11 ----------
arch/s390/Kconfig | 5 ++---
arch/s390/Kconfig.debug | 3 ---
arch/x86/Kconfig | 5 ++---
arch/x86/Kconfig.debug | 11 ----------
13 files changed, 51 insertions(+), 68 deletions(-)

diff --git a/Documentation/security/self-protection.txt b/Documentation/security/self-protection.txt
index 3010576..f41dd00 100644
--- a/Documentation/security/self-protection.txt
+++ b/Documentation/security/self-protection.txt
@@ -56,6 +56,12 @@ CONFIG_DEBUG_SET_MODULE_RONX, which seek to make sure that code is not
writable, data is not executable, and read-only data is neither writable
nor executable.

+Most architectures have these options on by default and not user selectable.
+For some architectures like arm that wish to have these be selectable,
+the architecture Kconfig can select ARCH_OPTIONAL_KERNEL_RWX to enable
+a Kconfig prompt. CONFIG_ARCH_OPTIONAL_KERNEL_RWX_DEFAULT determines
+the default setting when ARCH_OPTIONAL_KERNEL_RWX is enabled.
+
#### Function pointers and sensitive variables must not be writable

Vast areas of kernel memory contain function pointers that are looked
diff --git a/arch/Kconfig b/arch/Kconfig
index 99839c2..3f8b8be 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -781,4 +781,38 @@ config VMAP_STACK
the stack to map directly to the KASAN shadow map using a formula
that is incorrect if the stack is in vmalloc space.

+config ARCH_OPTIONAL_KERNEL_RWX
+ def_bool n
+
+config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
+ def_bool n
+
+config ARCH_HAS_STRICT_KERNEL_RWX
+ def_bool n
+
+config DEBUG_RODATA
+ bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
+ depends on ARCH_HAS_STRICT_KERNEL_RWX
+ default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
+ help
+ If this is set, kernel text and rodata memory will be made read-only,
+ and non-text memory will be made non-executable. This provides
+ protection against certain security exploits (e.g. executing the heap
+ or modifying text)
+
+ These features are considered standard security practice these days.
+ You should say Y here in almost all cases.
+
+config ARCH_HAS_STRICT_MODULE_RWX
+ def_bool n
+
+config DEBUG_SET_MODULE_RONX
+ bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
+ depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
+ default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
+ 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 exploits (e.g. writing to text)
+
source "kernel/gcov/Kconfig"
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 186c4c2..8748353 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -4,10 +4,14 @@ config ARM
select ARCH_CLOCKSOURCE_DATA
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_ELF_RANDOMIZE
+ select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
+ select ARCH_HAS_STRICT_MODULE_RWX if MMU
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAVE_CUSTOM_GPIO_H
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_MIGHT_HAVE_PC_PARPORT
+ select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
+ select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
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
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index f68e8ec..419a035 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1051,18 +1051,6 @@ config ARCH_SUPPORTS_BIG_ENDIAN
This option specifies the architecture can support big endian
operation.

-config DEBUG_RODATA
- bool "Make kernel text and rodata read-only"
- depends on MMU && !XIP_KERNEL
- default y if CPU_V7
- help
- If this is set, kernel text and rodata memory will be made
- read-only, and non-text kernel memory will be made non-executable.
- The tradeoff is that each region is padded to section-size (1MiB)
- boundaries (because their permissions are different and splitting
- the 1M pages into 4K ones causes TLB performance problems), which
- can waste memory.
-
config DEBUG_ALIGN_RODATA
bool "Make rodata strictly non-executable"
depends on DEBUG_RODATA
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1117421..e1efbcc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -13,6 +13,8 @@ config ARM64
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_KCOV
select ARCH_HAS_SG_CHAIN
+ select ARCH_HAS_STRICT_KERNEL_RWX
+ select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_SUPPORTS_ATOMIC_RMW
@@ -123,9 +125,6 @@ config ARCH_PHYS_ADDR_T_64BIT
config MMU
def_bool y

-config DEBUG_RODATA
- def_bool y
-
config ARM64_PAGE_SHIFT
int
default 16 if ARM64_64K_PAGES
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index d1ebd46..939815e 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 DEBUG_RODATA
bool "Align linker sections up to SECTION_SIZE"
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 3a71f38..ad294b3 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -8,6 +8,7 @@ config PARISC
select HAVE_SYSCALL_TRACEPOINTS
select ARCH_WANT_FRAME_POINTERS
select ARCH_HAS_ELF_RANDOMIZE
+ select ARCH_HAS_STRICT_KERNEL_RWX
select RTC_CLASS
select RTC_DRV_GENERIC
select INIT_ALL_POSSIBLE
diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
index 68b7cbd..0d856b9 100644
--- a/arch/parisc/Kconfig.debug
+++ b/arch/parisc/Kconfig.debug
@@ -5,15 +5,4 @@ source "lib/Kconfig.debug"
config TRACE_IRQFLAGS_SUPPORT
def_bool y

-config DEBUG_RODATA
- bool "Write protect kernel read-only data structures"
- depends on DEBUG_KERNEL
- default y
- help
- Mark the kernel read-only data as write-protected in the pagetables,
- in order to catch accidental (and incorrect) writes to such const
- data. This option may have a slight performance impact because a
- portion of the kernel code won't be covered by a TLB anymore.
- If in doubt, say "N".
-
endmenu
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index c6722112..53bb0e3 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -62,9 +62,6 @@ config PCI_QUIRKS
config ARCH_SUPPORTS_UPROBES
def_bool y

-config DEBUG_RODATA
- def_bool y
-
config S390
def_bool y
select ARCH_HAS_DEVMEM_IS_ALLOWED
@@ -73,6 +70,8 @@ config S390
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_KCOV
select ARCH_HAS_SG_CHAIN
+ select ARCH_HAS_STRICT_KERNEL_RWX
+ select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_INLINE_READ_LOCK
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 e487493..13e1bf4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,8 @@ config X86
select ARCH_HAS_MMIO_FLUSH
select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_SG_CHAIN
+ select ARCH_HAS_STRICT_KERNEL_RWX
+ select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
@@ -309,9 +311,6 @@ config ARCH_SUPPORTS_UPROBES
config FIX_EARLYCON_MEM
def_bool y

-config DEBUG_RODATA
- def_bool y
-
config PGTABLE_LEVELS
int
default 4 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
--
2.7.4

Next message: Laura Abbott: "[PATCHv3 2/2] arch: Rename CONFIG_DEBUG_RODATA and CONFIG_DEBUG_MODULE_RONX"
Previous message: Laura Abbott: "[PATCHv3 0/2] Hardening configs refactor/rename"
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Next in thread: Ingo Molnar: "Re: [PATCHv3 1/2] arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common"
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