kasan: adjust kasan_stack_oob for tag-based mode

Use OOB_TAG_OFF as access offset to land the access into the next granule.

Suggested-by: Walter Wu <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Elena Petrova <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Link: http://lkml.kernel.org/r/403b259f1de49a7a3694531c851ac28326a586a8.1596199677.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/3063ab1411e92bce36061a96e25b651212e70ba6.1596544734.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds <[email protected]>

lib/test_kasan.c

@@ -488,7 +488,7 @@ static noinline void __init kasan_global_oob(void)
 static noinline void __init kasan_stack_oob(void)
 {
 	char stack_array[10];
-	volatile int i = 0;
+	volatile int i = OOB_TAG_OFF;
 	char *p = &stack_array[ARRAY_SIZE(stack_array) + i];
 
 	pr_info("out-of-bounds on stack\n");