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ARM: initial stack protector (-fstack-protector) support

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This is the very basic stuff without the changing canary upon
task switch yet.  Just the Kconfig option and a constant canary
value initialized at boot time.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
This commit is contained in:
Nicolas Pitre 2010-05-24 23:55:42 -04:00
parent cc92c28b2d
commit c743f38013
4 changed files with 60 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

12
arch/arm/Kconfig
View file

@ -1374,6 +1374,18 @@ config UACCESS_WITH_MEMCPY
However, if the CPU data cache is using a write-allocate mode,
this option is unlikely to provide any performance gain.
config CC_STACKPROTECTOR
bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
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.
endmenu
menu "Boot options"

4
arch/arm/Makefile
View file

@ -34,6 +34,10 @@ ifeq ($(CONFIG_FRAME_POINTER),y)
KBUILD_CFLAGS +=-fno-omit-frame-pointer -mapcs -mno-sched-prolog
endif
ifeq ($(CONFIG_CC_STACKPROTECTOR),y)
KBUILD_CFLAGS +=-fstack-protector
endif
ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
KBUILD_CPPFLAGS += -mbig-endian
AS += -EB

38
arch/arm/include/asm/stackprotector.h Normal file
View file

@ -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 <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 */

6
arch/arm/kernel/process.c
View file

@ -37,6 +37,12 @@
#include <asm/stacktrace.h>
#include <asm/mach/time.h>
#ifdef CONFIG_CC_STACKPROTECTOR
#include <linux/stackprotector.h>
unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif
static const char *processor_modes[] = {
"USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" , "UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
"UK8_26" , "UK9_26" , "UK10_26", "UK11_26", "UK12_26", "UK13_26", "UK14_26", "UK15_26",