[PATCH v7 2/2] mm, kasan: switch SLUB to stackdepot, enable memory quarantine for SLUB

From: Alexander Potapenko
Date: Tue Jul 12 2016 - 14:13:16 EST

For KASAN builds:
- switch SLUB allocator to using stackdepot instead of storing the
allocation/deallocation stacks in the objects;
- change the freelist hook so that parts of the freelist can be put
into the quarantine.

Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
v7: - addressed comments by Andrey Ryabinin:
- split the nearest_obj() fix into a separate patch
- introduce kasan_metadata_size()
- move KASAN definitions back to mm/kasan/kasan.h
- fix minor nits
- addressed comments by Joonsoo Kim:
- always return the unchanged freelist pointer from slab_free_hook()
- account for KASAN metadata size in print_trailer()
- fix minor nits
v6: - addressed comments by Andrey Ryabinin:
- move nearest_obj() back to header files
- fix check_pad_bytes() to address problems with poisoning
- don't define __OBJECT_POISON to 0
- simplify slab_free_freelist_hook() implementation
- move KASAN definintions used by SLUB code to include/linux/kasan.h
- fix minor nits
v5: - addressed comments by Andrey Ryabinin:
- don't define SLAB_RED_ZONE, SLAB_POISON, SLAB_STORE_USER to 0
- account for left redzone size when SLAB_RED_ZONE is used
- incidentally moved the implementations of nearest_obj() to mm/sl[au]b.c
v4: - addressed comments by Andrey Ryabinin:
- don't set slub_debug by default for everyone;
- introduce the ___cache_free() helper function.
v3: - addressed comments by Andrey Ryabinin:
- replaced KMALLOC_MAX_CACHE_SIZE with KMALLOC_MAX_SIZE in
kasan_cache_create();
- for caches with SLAB_KASAN flag set, their alloc_meta_offset and
free_meta_offset are always valid.
v2: - incorporated kbuild fixes by Andrew Morton

---
include/linux/kasan.h | 2 ++
include/linux/slab_def.h | 3 ++-
include/linux/slub_def.h | 4 +++
lib/Kconfig.kasan | 4 +--
mm/kasan/Makefile | 3 +--
mm/kasan/kasan.c | 64 +++++++++++++++++++++++++++---------------------
mm/kasan/kasan.h | 3 +--
mm/kasan/report.c | 8 +++---
mm/slab.h | 2 ++
mm/slub.c | 57 ++++++++++++++++++++++++++++++++----------
10 files changed, 97 insertions(+), 53 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index ac4b3c4..c9cf374 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -77,6 +77,7 @@ void kasan_free_shadow(const struct vm_struct *vm);

size_t ksize(const void *);
static inline void kasan_unpoison_slab(const void *ptr) { ksize(ptr); }
+size_t kasan_metadata_size(struct kmem_cache *cache);

#else /* CONFIG_KASAN */

@@ -121,6 +122,7 @@ static inline int kasan_module_alloc(void *addr, size_t size) { return 0; }
static inline void kasan_free_shadow(const struct vm_struct *vm) {}

static inline void kasan_unpoison_slab(const void *ptr) { }
+static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }

#endif /* CONFIG_KASAN */

diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 8694f7a..6f35df7 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -88,7 +88,8 @@ struct kmem_cache {
};

static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
- void *x) {
+ void *x)
+{
void *object = x - (x - page->s_mem) % cache->size;
void *last_object = page->s_mem + (cache->num - 1) * cache->size;

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index b71b258..3b80dec 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -99,6 +99,10 @@ struct kmem_cache {
*/
int remote_node_defrag_ratio;
#endif
+#ifdef CONFIG_KASAN
+ struct kasan_cache kasan_info;
+#endif
+
struct kmem_cache_node *node[MAX_NUMNODES];
};

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 67d8c68..bd38aab 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -5,9 +5,9 @@ if HAVE_ARCH_KASAN

config KASAN
bool "KASan: runtime memory debugger"
- depends on SLUB_DEBUG || (SLAB && !DEBUG_SLAB)
+ depends on SLUB || (SLAB && !DEBUG_SLAB)
select CONSTRUCTORS
- select STACKDEPOT if SLAB
+ select STACKDEPOT
help
Enables kernel address sanitizer - runtime memory debugger,
designed to find out-of-bounds accesses and use-after-free bugs.
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 1548749..2976a9e 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -7,5 +7,4 @@ CFLAGS_REMOVE_kasan.o = -pg
# see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

-obj-y := kasan.o report.o kasan_init.o
-obj-$(CONFIG_SLAB) += quarantine.o
+obj-y := kasan.o report.o kasan_init.o quarantine.o
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 6845f92..d92a7a2 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -351,7 +351,6 @@ void kasan_free_pages(struct page *page, unsigned int order)
KASAN_FREE_PAGE);
}

-#ifdef CONFIG_SLAB
/*
* Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
* For larger allocations larger redzones are used.
@@ -373,16 +372,10 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
unsigned long *flags)
{
int redzone_adjust;
- /* Make sure the adjusted size is still less than
- * KMALLOC_MAX_CACHE_SIZE.
- * TODO: this check is only useful for SLAB, but not SLUB. We'll need
- * to skip it for SLUB when it starts using kasan_cache_create().
- */
- if (*size > KMALLOC_MAX_CACHE_SIZE -
- sizeof(struct kasan_alloc_meta) -
- sizeof(struct kasan_free_meta))
- return;
- *flags |= SLAB_KASAN;
+#ifdef CONFIG_SLAB
+ int orig_size = *size;
+#endif
+
/* Add alloc meta. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
@@ -395,14 +388,31 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
}
redzone_adjust = optimal_redzone(cache->object_size) -
(*size - cache->object_size);
+
if (redzone_adjust > 0)
*size += redzone_adjust;
- *size = min(KMALLOC_MAX_CACHE_SIZE,
+
+#ifdef CONFIG_SLAB
+ *size = min(KMALLOC_MAX_SIZE,
max(*size,
cache->object_size +
optimal_redzone(cache->object_size)));
-}
+ /*
+ * If the metadata doesn't fit, don't enable KASAN at all.
+ */
+ if (*size <= cache->kasan_info.alloc_meta_offset ||
+ *size <= cache->kasan_info.free_meta_offset) {
+ *size = orig_size;
+ return;
+ }
+#else
+ *size = max(*size,
+ cache->object_size +
+ optimal_redzone(cache->object_size));
+
#endif
+ *flags |= SLAB_KASAN;
+}

void kasan_cache_shrink(struct kmem_cache *cache)
{
@@ -414,6 +424,14 @@ void kasan_cache_destroy(struct kmem_cache *cache)
quarantine_remove_cache(cache);
}

+size_t kasan_metadata_size(struct kmem_cache *cache)
+{
+ return (cache->kasan_info.alloc_meta_offset ?
+ sizeof(struct kasan_alloc_meta) : 0) +
+ (cache->kasan_info.free_meta_offset ?
+ sizeof(struct kasan_free_meta) : 0);
+}
+
void kasan_poison_slab(struct page *page)
{
kasan_poison_shadow(page_address(page),
@@ -431,16 +449,13 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
kasan_poison_shadow(object,
round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
KASAN_KMALLOC_REDZONE);
-#ifdef CONFIG_SLAB
if (cache->flags & SLAB_KASAN) {
struct kasan_alloc_meta *alloc_info =
get_alloc_info(cache, object);
alloc_info->state = KASAN_STATE_INIT;
}
-#endif
}

-#ifdef CONFIG_SLAB
static inline int in_irqentry_text(unsigned long ptr)
{
return (ptr >= (unsigned long)&__irqentry_text_start &&
@@ -501,7 +516,6 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
return (void *)object + cache->kasan_info.free_meta_offset;
}
-#endif

void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
{
@@ -522,16 +536,16 @@ static void kasan_poison_slab_free(struct kmem_cache *cache, void *object)

bool kasan_slab_free(struct kmem_cache *cache, void *object)
{
-#ifdef CONFIG_SLAB
/* RCU slabs could be legally used after free within the RCU period */
if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
return false;

if (likely(cache->flags & SLAB_KASAN)) {
- struct kasan_alloc_meta *alloc_info =
- get_alloc_info(cache, object);
- struct kasan_free_meta *free_info =
- get_free_info(cache, object);
+ struct kasan_alloc_meta *alloc_info;
+ struct kasan_free_meta *free_info;
+
+ alloc_info = get_alloc_info(cache, object);
+ free_info = get_free_info(cache, object);

switch (alloc_info->state) {
case KASAN_STATE_ALLOC:
@@ -550,10 +564,6 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object)
}
}
return false;
-#else
- kasan_poison_slab_free(cache, object);
- return false;
-#endif
}

void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
@@ -576,7 +586,6 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
kasan_unpoison_shadow(object, size);
kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
KASAN_KMALLOC_REDZONE);
-#ifdef CONFIG_SLAB
if (cache->flags & SLAB_KASAN) {
struct kasan_alloc_meta *alloc_info =
get_alloc_info(cache, object);
@@ -585,7 +594,6 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
alloc_info->alloc_size = size;
set_track(&alloc_info->track, flags);
}
-#endif
}
EXPORT_SYMBOL(kasan_kmalloc);

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index fb87923..31972cd 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -95,7 +95,6 @@ struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
const void *object);

-
static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
{
return (void *)(((unsigned long)shadow_addr - KASAN_SHADOW_OFFSET)
@@ -110,7 +109,7 @@ static inline bool kasan_report_enabled(void)
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip);

-#ifdef CONFIG_SLAB
+#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
void quarantine_reduce(void);
void quarantine_remove_cache(struct kmem_cache *cache);
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index b3c122d..861b977 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -116,7 +116,6 @@ static inline bool init_task_stack_addr(const void *addr)
sizeof(init_thread_union.stack));
}

-#ifdef CONFIG_SLAB
static void print_track(struct kasan_track *track)
{
pr_err("PID = %u\n", track->pid);
@@ -130,8 +129,8 @@ static void print_track(struct kasan_track *track)
}
}

-static void object_err(struct kmem_cache *cache, struct page *page,
- void *object, char *unused_reason)
+static void kasan_object_err(struct kmem_cache *cache, struct page *page,
+ void *object, char *unused_reason)
{
struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
struct kasan_free_meta *free_info;
@@ -162,7 +161,6 @@ static void object_err(struct kmem_cache *cache, struct page *page,
break;
}
}
-#endif

static void print_address_description(struct kasan_access_info *info)
{
@@ -177,7 +175,7 @@ static void print_address_description(struct kasan_access_info *info)
struct kmem_cache *cache = page->slab_cache;
object = nearest_obj(cache, page,
(void *)info->access_addr);
- object_err(cache, page, object,
+ kasan_object_err(cache, page, object,
"kasan: bad access detected");
return;
}
diff --git a/mm/slab.h b/mm/slab.h
index dedb1a9..d1e6f14 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -366,6 +366,8 @@ static inline size_t slab_ksize(const struct kmem_cache *s)
if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
return s->object_size;
# endif
+ if (s->flags & SLAB_KASAN)
+ return s->object_size;
/*
* If we have the need to store the freelist pointer
* back there or track user information then we can
diff --git a/mm/slub.c b/mm/slub.c
index 27cbef9..d9a8c98 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -454,8 +454,6 @@ static inline void *restore_red_left(struct kmem_cache *s, void *p)
*/
#if defined(CONFIG_SLUB_DEBUG_ON)
static int slub_debug = DEBUG_DEFAULT_FLAGS;
-#elif defined(CONFIG_KASAN)
-static int slub_debug = SLAB_STORE_USER;
#else
static int slub_debug;
#endif
@@ -660,6 +658,8 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
if (s->flags & SLAB_STORE_USER)
off += 2 * sizeof(struct track);

+ off += kasan_metadata_size(s);
+
if (off != size_from_object(s))
/* Beginning of the filler is the free pointer */
print_section("Padding ", p + off, size_from_object(s) - off);
@@ -787,6 +787,8 @@ static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
/* We also have user information there */
off += 2 * sizeof(struct track);

+ off += kasan_metadata_size(s);
+
if (size_from_object(s) == off)
return 1;

@@ -1322,8 +1324,10 @@ static inline void kfree_hook(const void *x)
kasan_kfree_large(x);
}

-static inline void slab_free_hook(struct kmem_cache *s, void *x)
+static inline void *slab_free_hook(struct kmem_cache *s, void *x)
{
+ void *freeptr;
+
kmemleak_free_recursive(x, s->flags);

/*
@@ -1344,7 +1348,13 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x)
if (!(s->flags & SLAB_DEBUG_OBJECTS))
debug_check_no_obj_freed(x, s->object_size);

+ freeptr = get_freepointer(s, x);
+ /*
+ * kasan_slab_free() may put x into memory quarantine, delaying its
+ * reuse. In this case the object's freelist pointer is changed.
+ */
kasan_slab_free(s, x);
+ return freeptr;
}

static inline void slab_free_freelist_hook(struct kmem_cache *s,
@@ -1362,11 +1372,11 @@ static inline void slab_free_freelist_hook(struct kmem_cache *s,

void *object = head;
void *tail_obj = tail ? : head;
+ void *freeptr;

do {
- slab_free_hook(s, object);
- } while ((object != tail_obj) &&
- (object = get_freepointer(s, object)));
+ freeptr = slab_free_hook(s, object);
+ } while ((object != tail_obj) && (object = freeptr));
#endif
}

@@ -2768,16 +2778,13 @@ slab_empty:
* same page) possible by specifying head and tail ptr, plus objects
* count (cnt). Bulk free indicated by tail pointer being set.
*/
-static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
- void *head, void *tail, int cnt,
- unsigned long addr)
+static __always_inline void do_slab_free(struct kmem_cache *s,
+ struct page *page, void *head, void *tail,
+ int cnt, unsigned long addr)
{
void *tail_obj = tail ? : head;
struct kmem_cache_cpu *c;
unsigned long tid;
-
- slab_free_freelist_hook(s, head, tail);
-
redo:
/*
* Determine the currently cpus per cpu slab.
@@ -2811,6 +2818,27 @@ redo:

}

+static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
+ void *head, void *tail, int cnt,
+ unsigned long addr)
+{
+ slab_free_freelist_hook(s, head, tail);
+ /*
+ * slab_free_freelist_hook() could have put the items into quarantine.
+ * If so, no need to free them.
+ */
+ if (s->flags & SLAB_KASAN && !(s->flags & SLAB_DESTROY_BY_RCU))
+ return;
+ do_slab_free(s, page, head, tail, cnt, addr);
+}
+
+#ifdef CONFIG_KASAN
+void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
+{
+ do_slab_free(cache, virt_to_head_page(x), x, NULL, 1, addr);
+}
+#endif
+
void kmem_cache_free(struct kmem_cache *s, void *x)
{
s = cache_from_obj(s, x);
@@ -3252,7 +3280,7 @@ static void set_min_partial(struct kmem_cache *s, unsigned long min)
static int calculate_sizes(struct kmem_cache *s, int forced_order)
{
unsigned long flags = s->flags;
- unsigned long size = s->object_size;
+ size_t size = s->object_size;
int order;

/*
@@ -3311,7 +3339,10 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
* the object.
*/
size += 2 * sizeof(struct track);
+#endif

+ kasan_cache_create(s, &size, &s->flags);
+#ifdef CONFIG_SLUB_DEBUG
if (flags & SLAB_RED_ZONE) {
/*
* Add some empty padding so that we can catch
--
2.8.0.rc3.226.g39d4020