kasan: save alloc stack traces for mempool

kasan: save alloc stack traces for mempool

Update kasan_mempool_unpoison_object to properly poison the redzone and
save alloc strack traces for kmalloc and slab pools.

As a part of this change, split out and use a unpoison_slab_object helper
function from __kasan_slab_alloc.

[[email protected]: mark unpoison_slab_object() as static]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/05ad235da8347cfe14d496d01b2aaf074b4f607c.1703024586.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Cc: Alexander Lobakin <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Breno Leitao <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Evgenii Stepanov <[email protected]>
Cc: Marco Elver <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>