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kasan: introduce kasan_init_cache_meta

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Add a kasan_init_cache_meta() helper that initializes metadata-related
cache parameters and use this helper in the common KASAN code.

Put the implementation of this new helper into generic.c, as only the
Generic mode uses per-object metadata.

Link: https://lkml.kernel.org/r/a6d7ea01876eb36472c9879f7b23f1b24766276e.1662411799.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-09-05 23:05:27 +02:00 committed by Andrew Morton
parent 284f8590a1
commit 5935143d11
3 changed files with 83 additions and 78 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
mm/kasan/common.c
View File

@ -118,28 +118,9 @@ void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
KASAN_PAGE_FREE, init);
}
/*
* Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
* For larger allocations larger redzones are used.
*/
static inline unsigned int optimal_redzone(unsigned int object_size)
{
return
object_size <= 64 - 16 ? 16 :
object_size <= 128 - 32 ? 32 :
object_size <= 512 - 64 ? 64 :
object_size <= 4096 - 128 ? 128 :
object_size <= (1 << 14) - 256 ? 256 :
object_size <= (1 << 15) - 512 ? 512 :
object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}
void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
slab_flags_t *flags)
{
unsigned int ok_size;
unsigned int optimal_size;
/*
* SLAB_KASAN is used to mark caches as ones that are sanitized by
* KASAN. Currently this flag is used in two places:
@ -149,65 +130,8 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
*/
*flags |= SLAB_KASAN;
if (!kasan_requires_meta())
return;
ok_size = *size;
/* Add alloc meta into redzone. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
/*
* If alloc meta doesn't fit, don't add it.
* This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
* to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
* larger sizes.
*/
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.alloc_meta_offset = 0;
*size = ok_size;
/* Continue, since free meta might still fit. */
}
/* Only the generic mode uses free meta or flexible redzones. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
return;
}
/*
* Add free meta into redzone when it's not possible to store
* it in the object. This is the case when:
* 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
* be touched after it was freed, or
* 2. Object has a constructor, which means it's expected to
* retain its content until the next allocation, or
* 3. Object is too small.
* Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
*/
if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
cache->object_size < sizeof(struct kasan_free_meta)) {
ok_size = *size;
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
/* If free meta doesn't fit, don't add it. */
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
*size = ok_size;
}
}
/* Calculate size with optimal redzone. */
optimal_size = cache->object_size + optimal_redzone(cache->object_size);
/* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
if (optimal_size > KMALLOC_MAX_SIZE)
optimal_size = KMALLOC_MAX_SIZE;
/* Use optimal size if the size with added metas is not large enough. */
if (*size < optimal_size)
*size = optimal_size;
if (kasan_requires_meta())
kasan_init_cache_meta(cache, size);
}
void __kasan_cache_create_kmalloc(struct kmem_cache *cache)

79
mm/kasan/generic.c
View File

@ -328,6 +328,85 @@ DEFINE_ASAN_SET_SHADOW(f3);
DEFINE_ASAN_SET_SHADOW(f5);
DEFINE_ASAN_SET_SHADOW(f8);
/*
* Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
* For larger allocations larger redzones are used.
*/
static inline unsigned int optimal_redzone(unsigned int object_size)
{
return
object_size <= 64 - 16 ? 16 :
object_size <= 128 - 32 ? 32 :
object_size <= 512 - 64 ? 64 :
object_size <= 4096 - 128 ? 128 :
object_size <= (1 << 14) - 256 ? 256 :
object_size <= (1 << 15) - 512 ? 512 :
object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}
void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size)
{
unsigned int ok_size;
unsigned int optimal_size;
ok_size = *size;
/* Add alloc meta into redzone. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
/*
* If alloc meta doesn't fit, don't add it.
* This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
* to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
* larger sizes.
*/
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.alloc_meta_offset = 0;
*size = ok_size;
/* Continue, since free meta might still fit. */
}
/* Only the generic mode uses free meta or flexible redzones. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
return;
}
/*
* Add free meta into redzone when it's not possible to store
* it in the object. This is the case when:
* 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
* be touched after it was freed, or
* 2. Object has a constructor, which means it's expected to
* retain its content until the next allocation, or
* 3. Object is too small.
* Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
*/
if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
cache->object_size < sizeof(struct kasan_free_meta)) {
ok_size = *size;
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
/* If free meta doesn't fit, don't add it. */
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
*size = ok_size;
}
}
/* Calculate size with optimal redzone. */
optimal_size = cache->object_size + optimal_redzone(cache->object_size);
/* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
if (optimal_size > KMALLOC_MAX_SIZE)
optimal_size = KMALLOC_MAX_SIZE;
/* Use optimal size if the size with added metas is not large enough. */
if (*size < optimal_size)
*size = optimal_size;
}
struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
const void *object)
{

2
mm/kasan/kasan.h
View File

@ -297,12 +297,14 @@ struct page *kasan_addr_to_page(const void *addr);
struct slab *kasan_addr_to_slab(const void *addr);
#ifdef CONFIG_KASAN_GENERIC
void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size);
void kasan_init_object_meta(struct kmem_cache *cache, const void *object);
struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
const void *object);
struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
const void *object);
#else
static inline void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size) { }
static inline void kasan_init_object_meta(struct kmem_cache *cache, const void *object) { }
#endif