slub: fix SLAB_CONSISTENCY_CHECKS + KASAN_SW_TAGS

Enabling SLUB_DEBUG's SLAB_CONSISTENCY_CHECKS with KASAN_SW_TAGS
triggers endless false positives during boot below due to
check_valid_pointer() checks tagged pointers which have no addresses
that is valid within slab pages:

  BUG radix_tree_node (Tainted: G    B            ): Freelist Pointer check fails
  -----------------------------------------------------------------------------

  INFO: Slab objects=69 used=69 fp=0x          (null) flags=0x7ffffffc000200
  INFO: Object @offset=15060037153926966016 fp=0x

  Redzone: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 18 6b 06 00 08 80 ff d0  .........k......
  Object : 18 6b 06 00 08 80 ff d0 00 00 00 00 00 00 00 00  .k..............
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Object : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  Redzone: bb bb bb bb bb bb bb bb                          ........
  Padding: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
  CPU: 0 PID: 0 Comm: swapper/0 Tainted: G    B             5.0.0-rc5+ torvalds#18
  Call trace:
    dump_backtrace+0x0/0x450
    show_stack+0x20/0x2c
    __dump_stack+0x20/0x28
    dump_stack+0xa0/0xfc
    print_trailer+0x1bc/0x1d0
    object_err+0x40/0x50
    alloc_debug_processing+0xf0/0x19c
    ___slab_alloc+0x554/0x704
    kmem_cache_alloc+0x2f8/0x440
    radix_tree_node_alloc+0x90/0x2fc
    idr_get_free+0x1e8/0x6d0
    idr_alloc_u32+0x11c/0x2a4
    idr_alloc+0x74/0xe0
    worker_pool_assign_id+0x5c/0xbc
    workqueue_init_early+0x49c/0xd50
    start_kernel+0x52c/0xac4
  FIX radix_tree_node: Marking all objects used

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Qian Cai <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/slub.c

@@ -513,6 +513,7 @@ static inline int check_valid_pointer(struct kmem_cache *s,
 		return 1;
 
 	base = page_address(page);
+	object = kasan_reset_tag(object);
 	object = restore_red_left(s, object);
 	if (object < base || object >= base + page->objects * s->size ||
 		(object - base) % s->size) {