[PATCH v6] mm, kasan: switch SLUB to stackdepot, enable memory quarantine for SLUB

From: Alexander Potapenko
Date: Fri Jul 08 2016 - 06:37:08 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>
---
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 | 23 ++++++++++++++++++
include/linux/slab_def.h | 3 ++-
include/linux/slub_def.h | 13 +++++++----
lib/Kconfig.kasan | 4 ++--
mm/kasan/Makefile | 3 +--
mm/kasan/kasan.c | 61 ++++++++++++++++++++++++++----------------------
mm/kasan/kasan.h | 26 +--------------------
mm/kasan/report.c | 8 +++----
mm/slab.h | 5 +++-
mm/slub.c | 44 +++++++++++++++++++++++++++-------
10 files changed, 114 insertions(+), 76 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 611927f..99b9ffc 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -2,6 +2,7 @@
#define _LINUX_KASAN_H

#include <linux/sched.h>
+#include <linux/stackdepot.h>
#include <linux/types.h>

struct kmem_cache;
@@ -20,6 +21,28 @@ extern pte_t kasan_zero_pte[PTRS_PER_PTE];
extern pmd_t kasan_zero_pmd[PTRS_PER_PMD];
extern pud_t kasan_zero_pud[PTRS_PER_PUD];

+struct kasan_track {
+ u32 pid;
+ depot_stack_handle_t stack;
+};
+
+struct kasan_alloc_meta {
+ struct kasan_track track;
+ u32 state : 2; /* enum kasan_state */
+ u32 alloc_size : 30;
+};
+
+struct qlist_node {
+ struct qlist_node *next;
+};
+struct kasan_free_meta {
+ /* This field is used while the object is in the quarantine.
+ * Otherwise it might be used for the allocator freelist.
+ */
+ struct qlist_node quarantine_link;
+ struct kasan_track track;
+};
+
void kasan_populate_zero_shadow(const void *shadow_start,
const void *shadow_end);

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 d1faa01..07e4549 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];
};

@@ -119,10 +123,11 @@ static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
void *object = x - (x - page_address(page)) % cache->size;
void *last_object = page_address(page) +
(page->objects - 1) * cache->size;
- if (unlikely(object > last_object))
- return last_object;
- else
- return object;
+ void *result = (unlikely(object > last_object)) ? last_object : object;
+
+ if (cache->flags & SLAB_RED_ZONE)
+ return ((char *)result + cache->red_left_pad);
+ return result;
}

#endif /* _LINUX_SLUB_DEF_H */
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 28439ac..03aa2a7 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);
@@ -392,17 +385,36 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
cache->object_size < sizeof(struct kasan_free_meta)) {
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
+ } else {
+ cache->kasan_info.free_meta_offset = 0;
}
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)
{
@@ -431,16 +443,13 @@ 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 +510,6 @@ 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 +530,16 @@ 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 +558,6 @@ 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,
@@ -568,6 +572,9 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
if (unlikely(object == NULL))
return;

+ if (!(cache->flags & SLAB_KASAN))
+ return;
+
redzone_start = round_up((unsigned long)(object + size),
KASAN_SHADOW_SCALE_SIZE);
redzone_end = round_up((unsigned long)object + cache->object_size,
@@ -576,7 +583,6 @@ 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 +591,6 @@ 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..d1dee1d 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -2,7 +2,6 @@
#define __MM_KASAN_KASAN_H

#include <linux/kasan.h>
-#include <linux/stackdepot.h>

#define KASAN_SHADOW_SCALE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
#define KASAN_SHADOW_MASK (KASAN_SHADOW_SCALE_SIZE - 1)
@@ -68,34 +67,11 @@ enum kasan_state {

#define KASAN_STACK_DEPTH 64

-struct kasan_track {
- u32 pid;
- depot_stack_handle_t stack;
-};
-
-struct kasan_alloc_meta {
- struct kasan_track track;
- u32 state : 2; /* enum kasan_state */
- u32 alloc_size : 30;
-};
-
-struct qlist_node {
- struct qlist_node *next;
-};
-struct kasan_free_meta {
- /* This field is used while the object is in the quarantine.
- * Otherwise it might be used for the allocator freelist.
- */
- struct qlist_node quarantine_link;
- struct kasan_track track;
-};
-
struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
const void *object);
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 +86,7 @@ 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..9a09d06 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
@@ -462,6 +464,7 @@ void *slab_next(struct seq_file *m, void *p, loff_t *pos);
void slab_stop(struct seq_file *m, void *p);
int memcg_slab_show(struct seq_file *m, void *p);

-void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr);
+void *nearest_obj(struct kmem_cache *cache, struct page *page, void *x);

+void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr);
#endif /* MM_SLAB_H */
diff --git a/mm/slub.c b/mm/slub.c
index 825ff45..72ecffa 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
@@ -783,6 +781,14 @@ static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
/* Freepointer is placed after the object. */
off += sizeof(void *);

+#ifdef CONFIG_KASAN
+ if (s->kasan_info.alloc_meta_offset)
+ off += sizeof(struct kasan_alloc_meta);
+
+ if (s->kasan_info.free_meta_offset)
+ off += sizeof(struct kasan_free_meta);
+#endif
+
if (s->flags & SLAB_STORE_USER)
/* We also have user information there */
off += 2 * sizeof(struct track);
@@ -1322,7 +1328,7 @@ 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 bool slab_free_hook(struct kmem_cache *s, void *x)
{
kmemleak_free_recursive(x, s->flags);

@@ -1344,7 +1350,7 @@ 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);

- kasan_slab_free(s, x);
+ return kasan_slab_free(s, x);
}

static inline void slab_free_freelist_hook(struct kmem_cache *s,
@@ -2753,6 +2759,9 @@ slab_empty:
discard_slab(s, page);
}

+static void do_slab_free(struct kmem_cache *s, struct page *page,
+ void *head, void *tail, int cnt, unsigned long addr);
+
/*
* Fastpath with forced inlining to produce a kfree and kmem_cache_free that
* can perform fastpath freeing without additional function calls.
@@ -2772,12 +2781,23 @@ 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);
+}
+
+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 +2831,11 @@ redo:

}

+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);
+}
+
void kmem_cache_free(struct kmem_cache *s, void *x)
{
s = cache_from_obj(s, x);
@@ -3252,7 +3277,7 @@ 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 +3336,10 @@ 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