kasan: test: rework kmalloc_oob_right

kasan: test: rework kmalloc_oob_right

Patch series "kasan: test: avoid crashing the kernel with HW_TAGS", v2.

KASAN tests do out-of-bounds and use-after-free accesses.  Running the
tests works fine for the GENERIC mode, as it uses qurantine and redzones.
But the HW_TAGS mode uses neither, and running the tests might crash the
kernel.

Rework the tests to avoid corrupting kernel memory.

This patch (of 8):

Rework kmalloc_oob_right() to do these bad access checks:

1. An unaligned access one byte past the requested kmalloc size
   (can only be detected by KASAN_GENERIC).
2. An aligned access into the first out-of-bounds granule that falls
   within the aligned kmalloc object.
3. Out-of-bounds access past the aligned kmalloc object.

Test #3 deliberately uses a read access to avoid corrupting memory.
Otherwise, this test might lead to crashes with the HW_TAGS mode, as it
neither uses quarantine nor redzones.

Link: https://lkml.kernel.org/r/cover.1628779805.git.andreyknvl@gmail.com
Link: https://lkml.kernel.org/r/474aa8b7b538c6737a4c6d0090350af2e1776bef.1628779805.git.andreyknvl@gmail.com
Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>