Commit 682ed089 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Andrew Morton
Browse files

kasan: only define kasan_cache_create for Generic mode 

Right now, kasan_cache_create() assigns SLAB_KASAN for all KASAN modes and
then sets up metadata-related cache parameters for the Generic mode.

SLAB_KASAN is used in two places:

1. In slab_ksize() to account for per-object metadata when
   calculating the size of the accessible memory within the object.
2. In slab_common.c via kasan_never_merge() to prevent merging of
   caches with per-object metadata.

Both cases are only relevant when per-object metadata is present, which is
only the case with the Generic mode.

Thus, assign SLAB_KASAN and define kasan_cache_create() only for the
Generic mode.

Also update the SLAB_KASAN-related comment.

Link: https://lkml.kernel.org/r/61faa2aa1906e2d02c97d00ddf99ce8911dda095.1662411799.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarMarco 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent be95e13f

include/linux/kasan.h

+6 −12
Original line number Diff line number Diff line
@@ -128,15 +128,6 @@ static __always_inline void kasan_unpoison_pages(struct page *page, 
		__kasan_unpoison_pages(page, order, init);

}



void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,

				slab_flags_t *flags);

static __always_inline void kasan_cache_create(struct kmem_cache *cache,

				unsigned int *size, slab_flags_t *flags)

{

	if (kasan_enabled())

		__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)

{
@@ -260,9 +251,6 @@ static inline void kasan_poison_pages(struct page *page, unsigned int order, 
				      bool init) {}

static inline void kasan_unpoison_pages(struct page *page, unsigned int order,

					bool init) {}

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 void kasan_poison_slab(struct slab *slab) {}

static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
@@ -316,6 +304,8 @@ static inline void kasan_unpoison_task_stack(struct task_struct *task) {} 


size_t kasan_metadata_size(struct kmem_cache *cache);

slab_flags_t kasan_never_merge(void);

void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,

			slab_flags_t *flags);



void kasan_cache_shrink(struct kmem_cache *cache);

void kasan_cache_shutdown(struct kmem_cache *cache);
@@ -334,6 +324,10 @@ static inline slab_flags_t kasan_never_merge(void) 
{

	return 0;

}

/* And no cache-related metadata initialization is required. */

static inline void kasan_cache_create(struct kmem_cache *cache,

				      unsigned int *size,

				      slab_flags_t *flags) {}



static inline void kasan_cache_shrink(struct kmem_cache *cache) {}

static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}

include/linux/slab.h

+1 −1
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ 
# define SLAB_ACCOUNT		0

#endif



#ifdef CONFIG_KASAN

#ifdef CONFIG_KASAN_GENERIC

#define SLAB_KASAN		((slab_flags_t __force)0x08000000U)

#else

#define SLAB_KASAN		0

mm/kasan/common.c

+0 −16
Original line number Diff line number Diff line
@@ -110,22 +110,6 @@ void __kasan_poison_pages(struct page *page, unsigned int order, bool init) 
			     KASAN_PAGE_FREE, init);

}



void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,

			  slab_flags_t *flags)

{

	/*

	 * SLAB_KASAN is used to mark caches as ones that are sanitized by

	 * KASAN. Currently this flag is used in two places:

	 * 1. In slab_ksize() when calculating the size of the accessible

	 *    memory within the object.

	 * 2. In slab_common.c to prevent merging of sanitized caches.

	 */

	*flags |= SLAB_KASAN;



	if (kasan_requires_meta())

		kasan_init_cache_meta(cache, size);

}



void __kasan_cache_create_kmalloc(struct kmem_cache *cache)

{

	cache->kasan_info.is_kmalloc = true;

mm/kasan/generic.c

+16 −1
Original line number Diff line number Diff line
@@ -352,11 +352,26 @@ static inline unsigned int optimal_redzone(unsigned int object_size) 
		object_size <= (1 << 16) - 1024 ? 1024 : 2048;

}



void kasan_init_cache_meta(struct kmem_cache *cache, unsigned int *size)

void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,

			  slab_flags_t *flags)

{

	unsigned int ok_size;

	unsigned int optimal_size;



	if (!kasan_requires_meta())

		return;



	/*

	 * SLAB_KASAN is used to mark caches that are sanitized by KASAN

	 * and that thus have per-object metadata.

	 * Currently this flag is used in two places:

	 * 1. In slab_ksize() to account for per-object metadata when

	 *    calculating the size of the accessible memory within the object.

	 * 2. In slab_common.c via kasan_never_merge() to prevent merging of

	 *    caches with per-object metadata.

	 */

	*flags |= SLAB_KASAN;



	ok_size = *size;



	/* Add alloc meta into redzone. */