[PATCH v3 mm 01/13] kasan, mm: don't save alloc stacks twice

Andrey Konovalov
2021-02-05T17:38:04Z

Currently KASAN saves allocation stacks in both kasan_slab_alloc() and
kasan_kmalloc() annotations. This patch changes KASAN to save allocation
stacks for slab objects from kmalloc caches in kasan_kmalloc() only,
and stacks for other slab objects in kasan_slab_alloc() only.

This change requires ____kasan_kmalloc() knowing whether the object
belongs to a kmalloc cache. This is implemented by adding a flag field
to the kasan_info structure. That flag is only set for kmalloc caches
via a new kasan_cache_create_kmalloc() annotation.

Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
include/linux/kasan.h | 9 +++++++++
mm/kasan/common.c | 18 ++++++++++++++----
mm/slab_common.c | 1 +
3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 1011e4f30284..e6ed969e74b3 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -83,6 +83,7 @@ static inline void kasan_disable_current(void) {}
struct kasan_cache {
int alloc_meta_offset;
int free_meta_offset;
+ bool is_kmalloc;
};

#ifdef CONFIG_KASAN_HW_TAGS
@@ -143,6 +144,13 @@ static __always_inline void kasan_cache_create(struct kmem_cache *cache,
__kasan_cache_create(cache, size, flags);
}

+void __kasan_cache_create_kmalloc(struct kmem_cache *cache);
+static __always_inline void kasan_cache_create_kmalloc(struct kmem_cache *cache)
+{
+ if (kasan_enabled())
+ __kasan_cache_create_kmalloc(cache);
+}
+
size_t __kasan_metadata_size(struct kmem_cache *cache);
static __always_inline size_t kasan_metadata_size(struct kmem_cache *cache)
{
@@ -278,6 +286,7 @@ static inline void kasan_free_pages(struct page *page, unsigned int order) {}
static inline void kasan_cache_create(struct kmem_cache *cache,
unsigned int *size,
slab_flags_t *flags) {}
+static inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) {}
static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
static inline void kasan_poison_slab(struct page *page) {}
static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index fe852f3cfa42..bfdf5464f4ef 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -210,6 +210,11 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
*size = optimal_size;
}

+void __kasan_cache_create_kmalloc(struct kmem_cache *cache)
+{
+ cache->kasan_info.is_kmalloc = true;
+}
+
size_t __kasan_metadata_size(struct kmem_cache *cache)
{
if (!kasan_stack_collection_enabled())
@@ -394,17 +399,22 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
}
}

-static void set_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
+static void set_alloc_info(struct kmem_cache *cache, void *object,
+ gfp_t flags, bool is_kmalloc)
{
struct kasan_alloc_meta *alloc_meta;

+ /* Don't save alloc info for kmalloc caches in kasan_slab_alloc(). */
+ if (cache->kasan_info.is_kmalloc && !is_kmalloc)
+ return;
+
alloc_meta = kasan_get_alloc_meta(cache, object);
if (alloc_meta)
kasan_set_track(&alloc_meta->alloc_track, flags);
}

static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
- size_t size, gfp_t flags, bool keep_tag)
+ size_t size, gfp_t flags, bool is_kmalloc)
{
unsigned long redzone_start;
unsigned long redzone_end;
@@ -423,7 +433,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
KASAN_GRANULE_SIZE);
redzone_end = round_up((unsigned long)object + cache->object_size,
KASAN_GRANULE_SIZE);
- tag = assign_tag(cache, object, false, keep_tag);
+ tag = assign_tag(cache, object, false, is_kmalloc);

/* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */
kasan_unpoison(set_tag(object, tag), size);
@@ -431,7 +441,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
KASAN_KMALLOC_REDZONE);

if (kasan_stack_collection_enabled())
- set_alloc_info(cache, (void *)object, flags);
+ set_alloc_info(cache, (void *)object, flags, is_kmalloc);

return set_tag(object, tag);
}
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 9aa3d2fe4c55..39d1a8ff9bb8 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -647,6 +647,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name,
panic("Out of memory when creating slab %s\n", name);

create_boot_cache(s, name, size, flags, useroffset, usersize);
+ kasan_cache_create_kmalloc(s);
list_add(&s->list, &slab_caches);
s->refcount = 1;
return s;
--
2.30.0.365.g02bc693789-goog