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
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"
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
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
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
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
config MMU
def_bool y
-config DEBUG_RODATA
- def_bool y
-
config ARM64_PAGE_SHIFT
int
default 16 if ARM64_64K_PAGES
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"
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
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
config ARCH_SUPPORTS_UPROBES
def_bool y
-config DEBUG_RODATA
- def_bool y
-
config S390
def_bool y
select ARCH_HAS_DEVMEM_IS_ALLOWED
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
kernel.
If in doubt, say "N"
-config DEBUG_SET_MODULE_RONX
- def_bool y
- depends on MODULES
endmenu
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
config FIX_EARLYCON_MEM
def_bool y
-config DEBUG_RODATA
- def_bool y
-
config PGTABLE_LEVELS
int
default 4 if X86_64
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
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