kasan, slub: handle pointer tags in early_kmem_cache_node_alloc

The previous patch updated KASAN hooks signatures and their usage in SLAB
and SLUB code, except for the early_kmem_cache_node_alloc function.  This
patch handles that function separately, as it requires to reorder some of
the initialization code to correctly propagate a tagged pointer in case a
tag is assigned by kasan_kmalloc.

Link: http://lkml.kernel.org/r/fc8d0fdcf733a7a52e8d0daaa650f4736a57de8c.1544099024.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -3364,16 +3364,16 @@ static void early_kmem_cache_node_alloc(int node)
 
 	n = page->freelist;
 	BUG_ON(!n);
-	page->freelist = get_freepointer(kmem_cache_node, n);
-	page->inuse = 1;
-	page->frozen = 0;
-	kmem_cache_node->node[node] = n;
 #ifdef CONFIG_SLUB_DEBUG
 	init_object(kmem_cache_node, n, SLUB_RED_ACTIVE);
 	init_tracking(kmem_cache_node, n);
 #endif
-	kasan_kmalloc(kmem_cache_node, n, sizeof(struct kmem_cache_node),
+	n = kasan_kmalloc(kmem_cache_node, n, sizeof(struct kmem_cache_node),
 		      GFP_KERNEL);
+	page->freelist = get_freepointer(kmem_cache_node, n);
+	page->inuse = 1;
+	page->frozen = 0;
+	kmem_cache_node->node[node] = n;
 	init_kmem_cache_node(n);
 	inc_slabs_node(kmem_cache_node, node, page->objects);