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 <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Konstantin Serebryany <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Andrey Konovalov 2015-11-05 18:51:01 -08:00 • committed by Linus Torvalds
commit cdf6a273dc

View file

@ -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: