| Message ID | 20171129215050.158653-2-paullawrence@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
/\/\/\/\/\/\On Wed, Nov 29, 2017 at 10:50 PM, Paul Lawrence <paullawrence@google.com> wrote: > 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. > > Signed-off-by: Greg Hackmann <ghackmann@google.com> > Signed-off-by: Paul Lawrence <paullawrence@google.com> > > mm/kasan/kasan.c | 32 ++++++++++++++++++++++++++++++++ > mm/kasan/kasan.h | 8 ++++++++ > mm/kasan/report.c | 4 ++++ > 3 files changed, 44 insertions(+) > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 405bba487df5..f86f862f41f8 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -736,6 +736,38 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size) > } > 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; > + > + 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, size); /\/\/\/\/\/\ Why do we need this? Stack must be clean. Compiler instrumentation does not clear shadow for objects in function prologue, if stack is dirty KASAN would explode. > + 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); We also need to poison [size, rounded_up_size) with partial value if the range is not empty. I.e. we can poison exactly, say, 3 bytes there. > +} > +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 --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index c70851a9a6a4..7c0bcd1f4c0d 100644 > --- a/mm/kasan/kasan.h > +++ b/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 --git a/mm/kasan/report.c b/mm/kasan/report.c > index 6bcfb01ba038..25419d426426 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) > 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; > -- > 2.15.0.531.g2ccb3012c9-goog > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 30, 2017 at 9:26 AM, Dmitry Vyukov <dvyukov@google.com> wrote: > /\/\/\/\/\/\On Wed, Nov 29, 2017 at 10:50 PM, Paul Lawrence > <paullawrence@google.com> wrote: >> 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. >> >> Signed-off-by: Greg Hackmann <ghackmann@google.com> >> Signed-off-by: Paul Lawrence <paullawrence@google.com> >> >> mm/kasan/kasan.c | 32 ++++++++++++++++++++++++++++++++ >> mm/kasan/kasan.h | 8 ++++++++ >> mm/kasan/report.c | 4 ++++ >> 3 files changed, 44 insertions(+) >> >> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c >> index 405bba487df5..f86f862f41f8 100644 >> --- a/mm/kasan/kasan.c >> +++ b/mm/kasan/kasan.c >> @@ -736,6 +736,38 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size) >> } >> 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; >> + >> + 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, size); > > /\/\/\/\/\/\ > > Why do we need this? Stack must be clean. Compiler instrumentation > does not clear shadow for objects in function prologue, if stack is > dirty KASAN would explode. > > >> + 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); > > We also need to poison [size, rounded_up_size) with partial value if > the range is not empty. I.e. we can poison exactly, say, 3 bytes > there. Wait, kasan_unpoison_shadow does this, right? Somewhat counter-intuitive and more expensive than needed. Let's poison only the last byte. >> +} >> +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 --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h >> index c70851a9a6a4..7c0bcd1f4c0d 100644 >> --- a/mm/kasan/kasan.h >> +++ b/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 --git a/mm/kasan/report.c b/mm/kasan/report.c >> index 6bcfb01ba038..25419d426426 100644 >> --- a/mm/kasan/report.c >> +++ b/mm/kasan/report.c >> @@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) >> 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; >> -- >> 2.15.0.531.g2ccb3012c9-goog >> -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 405bba487df5..f86f862f41f8 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -736,6 +736,38 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size) } 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; + + 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, 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 --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index c70851a9a6a4..7c0bcd1f4c0d 100644 --- a/mm/kasan/kasan.h +++ b/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 --git a/mm/kasan/report.c b/mm/kasan/report.c index 6bcfb01ba038..25419d426426 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info) 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;