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authorPaul Lawrence <paullawrence@google.com>2018-02-06 15:36:11 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-06 18:32:42 -0800
commit342061ee4ef3d80001d1ae494378f3979c861dba (patch)
tree0441486ae0c2df8e8edad38a70aa62515235eb02 /mm
parent1a69e7ce8391a8bc808baf04e06d88ab4024ca47 (diff)
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@google.com Signed-off-by: Greg Hackmann <ghackmann@google.com> Signed-off-by: Paul Lawrence <paullawrence@google.com> Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Matthias Kaehlcke <mka@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/kasan/kasan.c34
-rw-r--r--mm/kasan/kasan.h8
-rw-r--r--mm/kasan/report.c4
3 files changed, 46 insertions, 0 deletions
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 405bba487df5..d96b36088b2f 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -736,6 +736,40 @@ 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;
+ 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 --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 410c8235e671..eff12e040498 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;