This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

For software KASAN modes the check is based on the value in the shadow
memory.  Hardware tag-based KASAN won't be using shadow, so hide the
implementation of the check in check_invalid_free().

Also simplify the code for software tag-based mode.

No functional changes for software modes.

Link: https://lkml.kernel.org/r/d01534a4b977f97d87515dc590e6348e1406de81.1606161801.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: NVincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: NMarco Elver <elver@google.com>
Reviewed-by: NAlexander Potapenko <glider@google.com>
Tested-by: NVincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>