From mboxrd@z Thu Jan 1 00:00:00 1970 From: lauraa@codeaurora.org (Laura Abbott) Date: Tue, 21 Jan 2014 09:26:06 -0800 Subject: [PATCH] arm64: Add CONFIG_CC_STACKPROTECTOR Message-ID: <1390325166-16840-1-git-send-email-lauraa@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org arm64 currently lacks support for -fstack-protector. Add similar functionality to arm to detect stack corruption. Cc: Will Deacon Cc: Catalin Marinas Signed-off-by: Laura Abbott --- arch/arm64/Kconfig | 12 +++++++++ arch/arm64/Makefile | 4 +++ arch/arm64/include/asm/stackprotector.h | 38 +++++++++++++++++++++++++++++++ arch/arm64/kernel/process.c | 9 +++++++ 4 files changed, 63 insertions(+), 0 deletions(-) create mode 100644 arch/arm64/include/asm/stackprotector.h diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 6d4dd22..4f86874 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -168,6 +168,18 @@ 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. + This feature requires gcc version 4.2 or above. + source kernel/Kconfig.preempt config HZ diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 2fceb71..1ce221e 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -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 diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h new file mode 100644 index 0000000..de00332 --- /dev/null +++ b/arch/arm64/include/asm/stackprotector.h @@ -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 1 + +#include +#include + +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 */ diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index de17c89..592d630 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -50,6 +50,12 @@ #include #include +#ifdef CONFIG_CC_STACKPROTECTOR +#include +unsigned long __stack_chk_guard __read_mostly; +EXPORT_SYMBOL(__stack_chk_guard); +#endif + static void setup_restart(void) { /* @@ -288,6 +294,9 @@ struct task_struct *__switch_to(struct task_struct *prev, { struct task_struct *last; +#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) + __stack_chk_guard = next->stack_canary; +#endif fpsimd_thread_switch(next); tls_thread_switch(next); hw_breakpoint_thread_switch(next); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation