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 <[email protected]>
Tested-by: Qian Cai <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Evgeniy Stepanov <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kostya Serebryany <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/kmemleak.c

@@ -574,6 +574,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
 	unsigned long flags;
 	struct kmemleak_object *object, *parent;
 	struct rb_node **link, *rb_parent;
+	unsigned long untagged_ptr;
 
 	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
 	if (!object) {
@@ -619,8 +620,9 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
 
 	write_lock_irqsave(&kmemleak_lock, flags);
 
-	min_addr = min(min_addr, ptr);
-	max_addr = max(max_addr, ptr + size);
+	untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
+	min_addr = min(min_addr, untagged_ptr);
+	max_addr = max(max_addr, untagged_ptr + size);
 	link = &object_tree_root.rb_node;
 	rb_parent = NULL;
 	while (*link) {
@@ -1333,6 +1335,7 @@ static void scan_block(void *_start, void *_end,
 	unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
 	unsigned long *end = _end - (BYTES_PER_POINTER - 1);
 	unsigned long flags;
+	unsigned long untagged_ptr;
 
 	read_lock_irqsave(&kmemleak_lock, flags);
 	for (ptr = start; ptr < end; ptr++) {
@@ -1347,7 +1350,8 @@ static void scan_block(void *_start, void *_end,
 		pointer = *ptr;
 		kasan_enable_current();
 
-		if (pointer < min_addr || pointer >= max_addr)
+		untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
+		if (untagged_ptr < min_addr || untagged_ptr >= max_addr)
 			continue;
 
 		/*

mm/slab.h

@@ -438,6 +438,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
 	flags &= gfp_allowed_mask;
 	for (i = 0; i < size; i++) {
 		p[i] = kasan_slab_alloc(s, p[i], flags);
+		/* As p[i] might get tagged, call kmemleak hook after KASAN. */
 		kmemleak_alloc_recursive(p[i], s->object_size, 1,
 					 s->flags, flags);
 	}

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;
 }

mm/slub.c

@@ -1375,6 +1375,7 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node,
 static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
 {
 	ptr = kasan_kmalloc_large(ptr, size, flags);
+	/* As ptr might get tagged, call kmemleak hook after KASAN. */
 	kmemleak_alloc(ptr, size, 1, flags);
 	return ptr;
 }