Commit b3cbd9bf authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Linus Torvalds
Browse files

mm/kasan: get rid of ->state in struct kasan_alloc_meta

The state of object currently tracked in two places - shadow memory, and
the ->state field in struct kasan_alloc_meta.  We can get rid of the
latter.  The will save us a little bit of memory.  Also, this allow us
to move free stack into struct kasan_alloc_meta, without increasing
memory consumption.  So now we should always know when the last time the
object was freed.  This may be useful for long delayed use-after-free
bugs.

As a side effect this fixes following UBSAN warning:
	UBSAN: Undefined behaviour in mm/kasan/quarantine.c:102:13
	member access within misaligned address ffff88000d1efebc for type 'struct qlist_node'
	which requires 8 byte alignment

Link: http://lkml.kernel.org/r/1470062715-14077-5-git-send-email-aryabinin@virtuozzo.com

Reported-by: default avatarkernel test robot <xiaolong.ye@intel.com>
Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 47b5c2a0
......@@ -56,6 +56,7 @@ void kasan_cache_destroy(struct kmem_cache *cache);
void kasan_poison_slab(struct page *page);
void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
void kasan_poison_object_data(struct kmem_cache *cache, void *object);
void kasan_init_slab_obj(struct kmem_cache *cache, const void *object);
void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);
void kasan_kfree_large(const void *ptr);
......@@ -102,6 +103,8 @@ static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
void *object) {}
static inline void kasan_poison_object_data(struct kmem_cache *cache,
void *object) {}
static inline void kasan_init_slab_obj(struct kmem_cache *cache,
const void *object) {}
static inline void kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags) {}
static inline void kasan_kfree_large(const void *ptr) {}
......
......@@ -442,11 +442,6 @@ 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);
if (cache->flags & SLAB_KASAN) {
struct kasan_alloc_meta *alloc_info =
get_alloc_info(cache, object);
alloc_info->state = KASAN_STATE_INIT;
}
}
static inline int in_irqentry_text(unsigned long ptr)
......@@ -510,6 +505,17 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
return (void *)object + cache->kasan_info.free_meta_offset;
}
void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
{
struct kasan_alloc_meta *alloc_info;
if (!(cache->flags & SLAB_KASAN))
return;
alloc_info = get_alloc_info(cache, object);
__memset(alloc_info, 0, sizeof(*alloc_info));
}
void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
{
kasan_kmalloc(cache, object, cache->object_size, flags);
......@@ -529,34 +535,27 @@ static void kasan_poison_slab_free(struct kmem_cache *cache, void *object)
bool kasan_slab_free(struct kmem_cache *cache, void *object)
{
s8 shadow_byte;
/* 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;
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:
alloc_info->state = KASAN_STATE_QUARANTINE;
set_track(&free_info->track, GFP_NOWAIT);
kasan_poison_slab_free(cache, object);
quarantine_put(free_info, cache);
return true;
case KASAN_STATE_QUARANTINE:
case KASAN_STATE_FREE:
shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
pr_err("Double free");
dump_stack();
break;
default:
break;
}
return true;
}
kasan_poison_slab_free(cache, object);
if (unlikely(!(cache->flags & SLAB_KASAN)))
return false;
set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
quarantine_put(get_free_info(cache, object), cache);
return true;
}
void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
......@@ -579,13 +578,9 @@ 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);
if (cache->flags & SLAB_KASAN) {
struct kasan_alloc_meta *alloc_info =
get_alloc_info(cache, object);
alloc_info->state = KASAN_STATE_ALLOC;
set_track(&alloc_info->track, flags);
}
if (cache->flags & SLAB_KASAN)
set_track(&get_alloc_info(cache, object)->alloc_track, flags);
}
EXPORT_SYMBOL(kasan_kmalloc);
......
......@@ -59,13 +59,6 @@ struct kasan_global {
* Structures to keep alloc and free tracks *
*/
enum kasan_state {
KASAN_STATE_INIT,
KASAN_STATE_ALLOC,
KASAN_STATE_QUARANTINE,
KASAN_STATE_FREE
};
#define KASAN_STACK_DEPTH 64
struct kasan_track {
......@@ -74,8 +67,8 @@ struct kasan_track {
};
struct kasan_alloc_meta {
struct kasan_track track;
u32 state;
struct kasan_track alloc_track;
struct kasan_track free_track;
};
struct qlist_node {
......@@ -86,7 +79,6 @@ struct kasan_free_meta {
* 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,
......
......@@ -144,13 +144,11 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
{
void *object = qlink_to_object(qlink, cache);
struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
unsigned long flags;
if (IS_ENABLED(CONFIG_SLAB))
local_irq_save(flags);
alloc_info->state = KASAN_STATE_FREE;
___cache_free(cache, object, _THIS_IP_);
if (IS_ENABLED(CONFIG_SLAB))
......
......@@ -133,7 +133,6 @@ 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;
dump_stack();
pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
......@@ -141,23 +140,11 @@ static void kasan_object_err(struct kmem_cache *cache, struct page *page,
if (!(cache->flags & SLAB_KASAN))
return;
switch (alloc_info->state) {
case KASAN_STATE_INIT:
pr_err("Object not allocated yet\n");
break;
case KASAN_STATE_ALLOC:
pr_err("Allocation:\n");
print_track(&alloc_info->track);
break;
case KASAN_STATE_FREE:
case KASAN_STATE_QUARANTINE:
free_info = get_free_info(cache, object);
pr_err("Allocation:\n");
print_track(&alloc_info->track);
pr_err("Deallocation:\n");
print_track(&free_info->track);
break;
}
pr_err("Allocated:\n");
print_track(&alloc_info->alloc_track);
pr_err("Freed:\n");
print_track(&alloc_info->free_track);
}
static void print_address_description(struct kasan_access_info *info)
......
......@@ -2604,9 +2604,11 @@ static void cache_init_objs(struct kmem_cache *cachep,
}
for (i = 0; i < cachep->num; i++) {
objp = index_to_obj(cachep, page, i);
kasan_init_slab_obj(cachep, objp);
/* constructor could break poison info */
if (DEBUG == 0 && cachep->ctor) {
objp = index_to_obj(cachep, page, i);
kasan_unpoison_object_data(cachep, objp);
cachep->ctor(objp);
kasan_poison_object_data(cachep, objp);
......
......@@ -1384,6 +1384,7 @@ static void setup_object(struct kmem_cache *s, struct page *page,
void *object)
{
setup_object_debug(s, page, object);
kasan_init_slab_obj(s, object);
if (unlikely(s->ctor)) {
kasan_unpoison_object_data(s, object);
s->ctor(object);
......
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