kasan: accurately determine the type of the bad access
Makes KASAN accurately determine the type of the bad access. If the shadow byte value is in the [0, KASAN_SHADOW_SCALE_SIZE) range we can look at the next shadow byte to determine the type of the access. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Konstantin Serebryany <kcc@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -50,15 +50,26 @@ static const void *find_first_bad_addr(const void *addr, size_t size)
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static void print_error_description(struct kasan_access_info *info)
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static void print_error_description(struct kasan_access_info *info)
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{
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{
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const char *bug_type = "unknown-crash";
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const char *bug_type = "unknown-crash";
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u8 shadow_val;
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u8 *shadow_addr;
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info->first_bad_addr = find_first_bad_addr(info->access_addr,
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info->first_bad_addr = find_first_bad_addr(info->access_addr,
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info->access_size);
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info->access_size);
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shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
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shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
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switch (shadow_val) {
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/*
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* If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
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* at the next shadow byte to determine the type of the bad access.
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*/
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if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
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shadow_addr++;
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switch (*shadow_addr) {
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case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
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case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
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/*
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* In theory it's still possible to see these shadow values
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* due to a data race in the kernel code.
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*/
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bug_type = "out-of-bounds";
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bug_type = "out-of-bounds";
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break;
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break;
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case KASAN_PAGE_REDZONE:
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case KASAN_PAGE_REDZONE:
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