[PATCH v2 3/5] kmemleak: account for tagged pointers when calculating pointer range

[Andrey Konovalov]

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.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
 mm/kmemleak.c    | 10 +++++++---
 mm/slab.h        |  1 +
 mm/slab_common.c |  1 +
 mm/slub.c        |  1 +
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f9d9dc250428..707fa5579f66 100644
--- a/mm/kmemleak.c
+++ b/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;
 
 		/*
diff --git a/mm/slab.h b/mm/slab.h
index 638ea1b25d39..384105318779 100644
--- a/mm/slab.h
+++ b/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);
 	}
diff --git a/mm/slab_common.c b/mm/slab_common.c
index fe524c8d0246..f9d89c1b5977 100644
--- a/mm/slab_common.c
+++ b/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;
 }
diff --git a/mm/slub.c b/mm/slub.c
index 4a3d7686902f..f5a451c49190 100644
--- a/mm/slub.c
+++ b/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;
 }
-- 
2.20.1.791.gb4d0f1c61a-goog