FROMLIST: kasan, scs: support tagged vmalloc mappings

Fix up the custom KASAN instrumentation for Shadow Call Stack to support
vmalloc() mappings and pointers being tagged.

- Use the tagged pointer returned by kasan_unpoison_vmalloc() in
  __scs_alloc() when calling memset() to avoid false-positives.

- Do not return a tagged Shadow Call Stack pointer from __scs_alloc(),
  as this might lead to conflicts with the instrumentation.

Link: https://lkml.kernel.org/r/2f6605e3a358cf64d73a05710cb3da356886ad29.1646233925.git.andreyknvl@google.com


Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
(cherry picked from commit bd2c296805cff9572080bf56807c16d1dd382260
 git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Link: https://lore.kernel.org/all/2f6605e3a358cf64d73a05710cb3da356886ad29.1646233925.git.andreyknvl@google.com/


Bug: 217222520
Bug: 222221793
Change-Id: I9e6e4cd303e0815a5b092ba6ec28638bd1f7bc2c
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>