arm64: Add CONFIG_CC_STACKPROTECTOR
PATCH v2 1/1 arm64: Add CONFIG_CC_STACKPROTECTOR
arm64 currently lacks support for -fstack-protector. Add similar functionality to arm to detect stack corruption.
Cc Will Deacon <[email protected]>
Cc Catalin Marinas <[email protected]>
Signed-off-by Laura Abbott <[email protected]>
--- arch/arm64/Kconfig | 11 +++++++++ arch/arm64/Makefile | 4 +++ arch/arm64/include/asm/stackprotector.h | 38 +++++++++++++++++++++++++++++++ arch/arm64/kernel/process.c | 6 +++++ 4 files changed, 59 insertions(+), 0 deletions(-) create mode 100644 arch/arm64/include/asm/stackprotector.h
arch/arm64/Kconfig +11 -0
@@ -168,6 +168,17 @@ config HOTPLUG_CPU Say Y here to experiment with turning CPUs off and on. CPUs can be controlled through /sys/devices/system/cpu. +config CC_STACKPROTECTOR + bool "Enable -fstack-protector buffer overflow detection" + help + This option turns on the -fstack-protector GCC feature. This + feature puts, at the beginning of functions, a canary value on + the stack just before the return address, and validates + the value just before actually returning. Stack based buffer + overflows (that need to overwrite this return address) now also + overwrite the canary, which gets detected and the attack is then + neutralized via a kernel panic. + source kernel/Kconfig.preempt config HZ
arch/arm64/Makefile +4 -0
@@ -48,6 +48,10 @@ core-$(CONFIG_XEN) += arch/arm64/xen/ libs-y := arch/arm64/lib/ $(libs-y) libs-y += $(LIBGCC) +ifeq ($(CONFIG_CC_STACKPROTECTOR),y) +KBUILD_CFLAGS +=-fstack-protector +endif + # Default target when executing plain make KBUILD_IMAGE := Image.gz KBUILD_DTBS := dtbs
arch/arm64/include/asm/stackprotector.h new file +38 -0
@@ -0,0 +1,38 @@ +/* +* GCC stack protector support. +* +* Stack protector works by putting predefined pattern at the start of +* the stack frame and verifying that it hasn't been overwritten when +* returning from the function. The pattern is called stack canary +* and gcc expects it to be defined by a global variable called +* "__stack_chk_guard" on ARM. This unfortunately means that on SMP +* we cannot have a different canary value per task. +*/ + +#ifndef __ASM_STACKPROTECTOR_H +#define __ASM_STACKPROTECTOR_H + +#include <linux/random.h> +#include <linux/version.h> + +extern unsigned long __stack_chk_guard; + +/* +* Initialize the stackprotector canary value. +* +* NOTE: this must only be called from functions that never return, +* and it must always be inlined. +*/ +static __always_inline void boot_init_stack_canary(void) +{ +unsigned long canary; + +/* Try to get a semi random initial value. */ +get_random_bytes (&canary,sizeof (canary)); + canary ^=LINUX_VERSION_CODE ; + + current->stack_canary = canary; + __stack_chk_guard = current->stack_canary; +} + +#endif /* _ASM_STACKPROTECTOR_H */
arch/arm64/kernel/process.c +6 -0
@@ -50,6 +50,12 @@#include <asm/processor.h> #include <asm/stacktrace.h> +#ifdef CONFIG_CC_STACKPROTECTOR +#include <linux/stackprotector.h> +unsigned long __stack_chk_guard__read_mostly ; +EXPORT_SYMBOL (__stack_chk_guard); +#endif +static void setup_restart (void ) {/*
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PATCH v2 1/1 arm64: Add CONFIG_CC_STACKPROTECTOR
Hi Laura,
Quoted 2 lines · Laura Abbott
arm64 currently lacks support for -fstack-protector. Add similar functionality to arm to detect stack corruption.
[...]
Quoted 5 lines
arch/arm64/include/asm/stackprotector.h new file +5
-0+/* +* Initialize the stackprotector canary value. +* +* NOTE: this must only be called from functions that never return, +* and it must always be inlined.
arch/arm64/include/asm/stackprotector.h line 34
Quoted 10 lines
arch/arm64/include/asm/stackprotector.h new file +10
-0+*/ +static __always_inline void boot_init_stack_canary(void) +{ +unsigned long canary; + +/* Try to get a semi random initial value. */ +get_random_bytes (&canary,sizeof (canary)); + canary ^=LINUX_VERSION_CODE ; + + current->stack_canary = canary;
Do we actually need this line now?
Will
PATCH v2 1/1 arm64: Add CONFIG_CC_STACKPROTECTOR
Quoted 17 lines · Will Deacon
Hi Laura,
Quoted 2 lines · Laura Abbott
arm64 currently lacks support for -fstack-protector. Add similar functionality to arm to detect stack corruption.
[...]
Quoted 9 lines
arch/arm64/include/asm/stackprotector.h new file +9
-0+/* +* Initialize the stackprotector canary value. +* +* NOTE: this must only be called from functions that never return, +* and it must always be inlined. +*/ +static __always_inline void boot_init_stack_canary(void) +{ +unsigned long canary;
Quoted 9 lines
arch/arm64/include/asm/stackprotector.h line 34
Quoted 6 lines
arch/arm64/include/asm/stackprotector.h new file +6
-0+ +/* Try to get a semi random initial value. */ +get_random_bytes (&canary,sizeof (canary)); + canary ^=LINUX_VERSION_CODE ; + + current->stack_canary = canary;Do we actually need this line now?
Probably not but it seems strange to not have anything there for the stack canary. Not sure if 'nothing' is better or worse than a possibly incorrect stack canary that gets automatically created in fork.
Laura
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