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>
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@ -736,6 +736,40 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size)
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}
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EXPORT_SYMBOL(__asan_unpoison_stack_memory);
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/* Emitted by compiler to poison alloca()ed objects. */
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void __asan_alloca_poison(unsigned long addr, size_t size)
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{
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size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
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size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
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rounded_up_size;
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size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE);
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const void *left_redzone = (const void *)(addr -
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KASAN_ALLOCA_REDZONE_SIZE);
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const void *right_redzone = (const void *)(addr + rounded_up_size);
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WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));
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kasan_unpoison_shadow((const void *)(addr + rounded_down_size),
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size - rounded_down_size);
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kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
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KASAN_ALLOCA_LEFT);
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kasan_poison_shadow(right_redzone,
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padding_size + KASAN_ALLOCA_REDZONE_SIZE,
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KASAN_ALLOCA_RIGHT);
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}
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EXPORT_SYMBOL(__asan_alloca_poison);
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/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
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void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
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{
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if (unlikely(!stack_top || stack_top > stack_bottom))
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return;
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kasan_unpoison_shadow(stack_top, stack_bottom - stack_top);
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}
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EXPORT_SYMBOL(__asan_allocas_unpoison);
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#ifdef CONFIG_MEMORY_HOTPLUG
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static int __meminit kasan_mem_notifier(struct notifier_block *nb,
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unsigned long action, void *data)
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@ -24,6 +24,14 @@
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#define KASAN_STACK_PARTIAL 0xF4
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#define KASAN_USE_AFTER_SCOPE 0xF8
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/*
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* alloca redzone shadow values
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*/
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#define KASAN_ALLOCA_LEFT 0xCA
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#define KASAN_ALLOCA_RIGHT 0xCB
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#define KASAN_ALLOCA_REDZONE_SIZE 32
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/* Don't break randconfig/all*config builds */
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#ifndef KASAN_ABI_VERSION
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#define KASAN_ABI_VERSION 1
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@ -102,6 +102,10 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info)
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case KASAN_USE_AFTER_SCOPE:
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bug_type = "use-after-scope";
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break;
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case KASAN_ALLOCA_LEFT:
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case KASAN_ALLOCA_RIGHT:
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bug_type = "alloca-out-of-bounds";
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break;
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}
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return bug_type;
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@ -32,7 +32,8 @@ else
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$(call cc-param,asan-globals=1) \
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$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
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$(call cc-param,asan-stack=1) \
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$(call cc-param,asan-use-after-scope=1)
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$(call cc-param,asan-use-after-scope=1) \
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$(call cc-param,asan-instrument-allocas=1)
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endif
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endif
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