CONFIG_KASAN_SW_TAGS=y not play well with kmemleak

[Qian Cai <cai@lca.pw>]

Kmemleak is totally busted with CONFIG_KASAN_SW_TAGS=y because most of tracking
object pointers passed to create_object() have the upper bits set by KASAN.
However, even after applied this patch [1] to fix a few things, it still has
many errors during boot.

https://git.sr.ht/~cai/linux-debug/tree/master/dmesg

What I don't understand is that even the patch did call kasan_reset_tag() in
paint_ptr(), it still complained on objects with upper bits set which indicates
that this line did not run.

return (__s64)(value << shift) >> shift;

[   42.462799] kmemleak: Trying to color unknown object at 0xffff80082df80000 as
Grey
[   42.470524] CPU: 128 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc5+ #17
[   42.477153] Call trace:
[   42.479639]  dump_backtrace+0x0/0x450
[   42.483362]  show_stack+0x20/0x2c
[   42.486733]  __dump_stack+0x20/0x28
[   42.490276]  dump_stack+0xa0/0xfc
[   42.493649]  paint_ptr+0xa8/0xf4
[   42.496934]  kmemleak_not_leak+0xa4/0x15c
[   42.501013]  init_section_page_ext+0x1bc/0x328
[   42.505528]  page_ext_init+0x4dc/0x75c
[   42.509336]  kernel_init_freeable+0x684/0x1104
[   42.513857]  kernel_init+0x18/0x2a4
[   42.517407]  ret_from_fork+0x10/0x18

[1]
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f9d9dc250428..70343d887f34 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -588,7 +588,7 @@ static struct kmemleak_object *create_object(unsigned long
ptr, size_t size,
        spin_lock_init(&object->lock);
        atomic_set(&object->use_count, 1);
        object->flags = OBJECT_ALLOCATED;
-       object->pointer = ptr;
+       object->pointer = (unsigned long)kasan_reset_tag((void *)ptr);
        object->size = size;
        object->excess_ref = 0;
        object->min_count = min_count;
@@ -748,11 +748,12 @@ static void paint_it(struct kmemleak_object *object, int
color)
 static void paint_ptr(unsigned long ptr, int color)
 {
        struct kmemleak_object *object;
+       unsigned long addr = (unsigned long)kasan_reset_tag((void *)ptr);

-       object = find_and_get_object(ptr, 0);
+       object = find_and_get_object(addr, 0);
        if (!object) {
                kmemleak_warn("Trying to color unknown object at 0x%08lx as %s\n",
-                             ptr,
+                             addr,
                              (color == KMEMLEAK_GREY) ? "Grey" :
                              (color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
                return;