kmemleak: account for tagged pointers when calculating pointer range

kmemleak keeps two global variables, min_addr and max_addr, which store
the range of valid (encountered by kmemleak) pointer values, which it
later uses to speed up pointer lookup when scanning blocks.

With tagged pointers this range will get bigger than it needs to be.  This
patch makes kmemleak untag pointers before saving them to min_addr and
max_addr and when performing a lookup.

Link: http://lkml.kernel.org/r/16e887d442986ab87fe87a755815ad92fa431a5f.1550066133.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Qian Cai <cai@lca.pw>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgeniy Stepanov <eugenis@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab_common.c

@@ -1229,6 +1229,7 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 	page = alloc_pages(flags, order);
 	ret = page ? page_address(page) : NULL;
 	ret = kasan_kmalloc_large(ret, size, flags);
+	/* As ret might get tagged, call kmemleak hook after KASAN. */
 	kmemleak_alloc(ret, size, 1, flags);
 	return ret;
 }