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kasan: accurately determine the type of the bad access

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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>
This commit is contained in:
Andrey Konovalov 2015-11-05 18:51:01 -08:00 committed by Linus Torvalds
parent 0952d87fd6
commit cdf6a273dc
1 changed files with 14 additions and 3 deletions
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17
mm/kasan/report.c
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@ -50,15 +50,26 @@ static const void *find_first_bad_addr(const void *addr, size_t size)
static void print_error_description(struct kasan_access_info *info)
{
const char *bug_type = "unknown-crash";
u8 shadow_val;
u8 *shadow_addr;
info->first_bad_addr = find_first_bad_addr(info->access_addr,
info->access_size);
shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
switch (shadow_val) {
/*
* If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
* at the next shadow byte to determine the type of the bad access.
*/
if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
shadow_addr++;
switch (*shadow_addr) {
case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
/*
* In theory it's still possible to see these shadow values
* due to a data race in the kernel code.
*/
bug_type = "out-of-bounds";
break;
case KASAN_PAGE_REDZONE: