Commit 284f8590 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Andrew Morton
Browse files

kasan: introduce kasan_requires_meta 

Add a kasan_requires_meta() helper that indicates whether the enabled
KASAN mode requires per-object metadata and use this helper in the common
code.

Also hide kasan_init_object_meta() under CONFIG_KASAN_GENERIC ifdef check,
as Generic is the only mode that uses per-object metadata.

To allow for a potential future change that makes Generic KASAN support
the kasan.stacktrace command-line parameter, let kasan_requires_meta()
return kasan_stack_collection_enabled() instead of simply returning true.

Link: https://lkml.kernel.org/r/cf837e9996246aaaeebf704ccf8ec26a34fcf64f.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 2f356801

mm/kasan/common.c

+5 −8
Original line number Diff line number Diff line
@@ -88,13 +88,10 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) 
}

#endif /* CONFIG_KASAN_STACK */



/*

 * Only allow cache merging when stack collection is disabled and no metadata

 * is present.

 */

/* Only allow cache merging when no per-object metadata is present. */

slab_flags_t __kasan_never_merge(void)

{

	if (kasan_stack_collection_enabled())

	if (kasan_requires_meta())

		return SLAB_KASAN;

	return 0;

}
@@ -152,7 +149,7 @@ void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 
	 */

	*flags |= SLAB_KASAN;



	if (!kasan_stack_collection_enabled())

	if (!kasan_requires_meta())

		return;



	ok_size = *size;
@@ -220,7 +217,7 @@ void __kasan_cache_create_kmalloc(struct kmem_cache *cache) 


size_t __kasan_metadata_size(struct kmem_cache *cache)

{

	if (!kasan_stack_collection_enabled())

	if (!kasan_requires_meta())

		return 0;

	return (cache->kasan_info.alloc_meta_offset ?

		sizeof(struct kasan_alloc_meta) : 0) +
@@ -295,7 +292,7 @@ void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache, 
						const void *object)

{

	/* Initialize per-object metadata if it is present. */

	if (kasan_stack_collection_enabled())

	if (kasan_requires_meta())

		kasan_init_object_meta(cache, object);



	/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */

mm/kasan/kasan.h

+29 −4
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ static inline bool kasan_sync_fault_possible(void) 
	return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM;

}



#else

#else /* CONFIG_KASAN_HW_TAGS */



static inline bool kasan_stack_collection_enabled(void)

{
@@ -60,7 +60,31 @@ static inline bool kasan_sync_fault_possible(void) 
	return true;

}



#endif

#endif /* CONFIG_KASAN_HW_TAGS */



#ifdef CONFIG_KASAN_GENERIC



/* Generic KASAN uses per-object metadata to store stack traces. */

static inline bool kasan_requires_meta(void)

{

	/*

	 * Technically, Generic KASAN always collects stack traces right now.

	 * However, let's use kasan_stack_collection_enabled() in case the

	 * kasan.stacktrace command-line argument is changed to affect

	 * Generic KASAN.

	 */

	return kasan_stack_collection_enabled();

}



#else /* CONFIG_KASAN_GENERIC */



/* Tag-based KASAN modes do not use per-object metadata. */

static inline bool kasan_requires_meta(void)

{

	return false;

}



#endif /* CONFIG_KASAN_GENERIC */



#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)

#define KASAN_GRANULE_SIZE	(1UL << KASAN_SHADOW_SCALE_SHIFT)
@@ -272,13 +296,14 @@ void kasan_report_invalid_free(void *object, unsigned long ip, enum kasan_report 
struct page *kasan_addr_to_page(const void *addr);

struct slab *kasan_addr_to_slab(const void *addr);



void kasan_init_object_meta(struct kmem_cache *cache, const void *object);



#ifdef CONFIG_KASAN_GENERIC

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_object_meta(struct kmem_cache *cache, const void *object) { }

#endif



depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc);

mm/kasan/tags.c

+0 −4
Original line number Diff line number Diff line
@@ -17,10 +17,6 @@ 


#include "kasan.h"



void kasan_init_object_meta(struct kmem_cache *cache, const void *object)

{

}



void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)

{

}