From: Paul Lawrence <paullawrence@xxxxxxxxxx> Subject: kasan: support alloca() poisoning clang's AddressSanitizer implementation adds redzones on either side of alloca()ed buffers. These redzones are 32-byte aligned and at least 32 bytes long. __asan_alloca_poison() is passed the size and address of the allocated buffer, *excluding* the redzones on either side. The left redzone will always be to the immediate left of this buffer; but AddressSanitizer may need to add padding between the end of the buffer and the right redzone. If there are any 8-byte chunks inside this padding, we should poison those too. __asan_allocas_unpoison() is just passed the top and bottom of the dynamic stack area, so unpoisoning is simpler. Link: http://lkml.kernel.org/r/20171204191735.132544-4-paullawrence@xxxxxxxxxx Signed-off-by: Greg Hackmann <ghackmann@xxxxxxxxxx> Signed-off-by: Paul Lawrence <paullawrence@xxxxxxxxxx> Acked-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> Cc: Matthias Kaehlcke <mka@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kasan/kasan.c | 34 ++++++++++++++++++++++++++++++++++ mm/kasan/kasan.h | 8 ++++++++ mm/kasan/report.c | 4 ++++ scripts/Makefile.kasan | 3 ++- 4 files changed, 48 insertions(+), 1 deletion(-) diff -puN mm/kasan/kasan.c~kasan-support-alloca-poisoning mm/kasan/kasan.c --- a/mm/kasan/kasan.c~kasan-support-alloca-poisoning +++ a/mm/kasan/kasan.c @@ -736,6 +736,40 @@ void __asan_unpoison_stack_memory(const } EXPORT_SYMBOL(__asan_unpoison_stack_memory); +/* Emitted by compiler to poison alloca()ed objects. */ +void __asan_alloca_poison(unsigned long addr, size_t size) +{ + size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE); + size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) - + rounded_up_size; + size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE); + + const void *left_redzone = (const void *)(addr - + KASAN_ALLOCA_REDZONE_SIZE); + const void *right_redzone = (const void *)(addr + rounded_up_size); + + WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE)); + + kasan_unpoison_shadow((const void *)(addr + rounded_down_size), + size - rounded_down_size); + kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE, + KASAN_ALLOCA_LEFT); + kasan_poison_shadow(right_redzone, + padding_size + KASAN_ALLOCA_REDZONE_SIZE, + KASAN_ALLOCA_RIGHT); +} +EXPORT_SYMBOL(__asan_alloca_poison); + +/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */ +void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom) +{ + if (unlikely(!stack_top || stack_top > stack_bottom)) + return; + + kasan_unpoison_shadow(stack_top, stack_bottom - stack_top); +} +EXPORT_SYMBOL(__asan_allocas_unpoison); + #ifdef CONFIG_MEMORY_HOTPLUG static int __meminit kasan_mem_notifier(struct notifier_block *nb, unsigned long action, void *data) diff -puN mm/kasan/kasan.h~kasan-support-alloca-poisoning mm/kasan/kasan.h --- a/mm/kasan/kasan.h~kasan-support-alloca-poisoning +++ a/mm/kasan/kasan.h @@ -24,6 +24,14 @@ #define KASAN_STACK_PARTIAL 0xF4 #define KASAN_USE_AFTER_SCOPE 0xF8 +/* + * alloca redzone shadow values + */ +#define KASAN_ALLOCA_LEFT 0xCA +#define KASAN_ALLOCA_RIGHT 0xCB + +#define KASAN_ALLOCA_REDZONE_SIZE 32 + /* Don't break randconfig/all*config builds */ #ifndef KASAN_ABI_VERSION #define KASAN_ABI_VERSION 1 diff -puN mm/kasan/report.c~kasan-support-alloca-poisoning mm/kasan/report.c --- a/mm/kasan/report.c~kasan-support-alloca-poisoning +++ a/mm/kasan/report.c @@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(s case KASAN_USE_AFTER_SCOPE: bug_type = "use-after-scope"; break; + case KASAN_ALLOCA_LEFT: + case KASAN_ALLOCA_RIGHT: + bug_type = "alloca-out-of-bounds"; + break; } return bug_type; diff -puN scripts/Makefile.kasan~kasan-support-alloca-poisoning scripts/Makefile.kasan --- a/scripts/Makefile.kasan~kasan-support-alloca-poisoning +++ a/scripts/Makefile.kasan @@ -32,7 +32,8 @@ else $(call cc-param,asan-globals=1) \ $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \ $(call cc-param,asan-stack=1) \ - $(call cc-param,asan-use-after-scope=1) + $(call cc-param,asan-use-after-scope=1) \ + $(call cc-param,asan-instrument-allocas=1) endif endif _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
