KASAN uses compiler instrumentation to intercept all memory accesses. But it does
not see memory accesses done in assembly code. One notable user of assembly code
is atomic operations. Frequently, for example, an atomic reference decrement is
the last access to an object and a good candidate for a racy use-after-free.

Add manual KASAN checks to atomic operations.
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>,
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/2fa6e7f0210fd20fe404e5b67e6e9213af2b69a1.1517246437.git.dvyukov@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>