diff options
| -rw-r--r-- | arch/arm/Kconfig | 12 | ||||
| -rw-r--r-- | arch/arm/Makefile | 4 | ||||
| -rw-r--r-- | arch/arm/include/asm/elf.h | 3 | ||||
| -rw-r--r-- | arch/arm/include/asm/stackprotector.h | 38 | ||||
| -rw-r--r-- | arch/arm/kernel/asm-offsets.c | 3 | ||||
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 8 | ||||
| -rw-r--r-- | arch/arm/kernel/process.c | 13 | ||||
| -rw-r--r-- | arch/arm/mm/mmap.c | 4 |
8 files changed, 85 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c171f35..2244de2 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1375,6 +1375,18 @@ 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" diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 64ba313..ddf6da1 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -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 diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h index 51662fe..0a96e8c 100644 --- a/arch/arm/include/asm/elf.h +++ b/arch/arm/include/asm/elf.h @@ -121,4 +121,7 @@ int dump_task_regs(struct task_struct *t, elf_gregset_t *elfregs); extern void elf_set_personality(const struct elf32_hdr *); #define SET_PERSONALITY(ex) elf_set_personality(&(ex)) +extern unsigned long arch_randomize_brk(struct mm_struct *mm); +#define arch_randomize_brk arch_randomize_brk + #endif diff --git a/arch/arm/include/asm/stackprotector.h b/arch/arm/include/asm/stackprotector.h new file mode 100644 index 0000000..de00332 --- /dev/null +++ b/arch/arm/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 <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 */ diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c index 8835115..85f2a01 100644 --- a/arch/arm/kernel/asm-offsets.c +++ b/arch/arm/kernel/asm-offsets.c @@ -40,6 +40,9 @@ int main(void) { DEFINE(TSK_ACTIVE_MM, offsetof(struct task_struct, active_mm)); +#ifdef CONFIG_CC_STACKPROTECTOR + DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); +#endif BLANK(); DEFINE(TI_FLAGS, offsetof(struct thread_info, flags)); DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count)); diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 7ee48e7..2d14081 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -745,6 +745,11 @@ ENTRY(__switch_to) mov r4, #0xffff0fff str r3, [r4, #-15] @ TLS val at 0xffff0ff0 #endif +#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) + ldr r7, [r2, #TI_TASK] + ldr r8, =__stack_chk_guard + ldr r7, [r7, #TSK_STACK_CANARY] +#endif #ifdef CONFIG_MMU mcr p15, 0, r6, c3, c0, 0 @ Set domain register #endif @@ -753,6 +758,9 @@ ENTRY(__switch_to) ldr r0, =thread_notify_head mov r1, #THREAD_NOTIFY_SWITCH bl atomic_notifier_call_chain +#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) + str r7, [r8] +#endif THUMB( mov ip, r4 ) mov r0, r5 ARM( ldmia r4, {r4 - sl, fp, sp, pc} ) @ Load all regs saved previously diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index acf5e6f..090ac94 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -28,6 +28,7 @@ #include <linux/tick.h> #include <linux/utsname.h> #include <linux/uaccess.h> +#include <linux/random.h> #include <asm/leds.h> #include <asm/processor.h> @@ -36,6 +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", @@ -421,3 +428,9 @@ unsigned long get_wchan(struct task_struct *p) } while (count ++ < 16); return 0; } + +unsigned long arch_randomize_brk(struct mm_struct *mm) +{ + unsigned long range_end = mm->brk + 0x02000000; + return randomize_range(mm->brk, range_end, 0) ? : mm->brk; +} diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index f5abc51..4f5b396 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -7,6 +7,7 @@ #include <linux/shm.h> #include <linux/sched.h> #include <linux/io.h> +#include <linux/random.h> #include <asm/cputype.h> #include <asm/system.h> @@ -80,6 +81,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, start_addr = addr = TASK_UNMAPPED_BASE; mm->cached_hole_size = 0; } + /* 8 bits of randomness in 20 address space bits */ + if (current->flags & PF_RANDOMIZE) + addr += (get_random_int() % (1 << 8)) << PAGE_SHIFT; full_search: if (do_align) |
