Commit af3751f3 authored by Daniel Axtens's avatar Daniel Axtens Committed by Linus Torvalds
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kasan: allow architectures to provide an outline readiness check 

Allow architectures to define a kasan_arch_is_ready() hook that bails out
of any function that's about to touch the shadow unless the arch says that
it is ready for the memory to be accessed.  This is fairly uninvasive and
should have a negligible performance penalty.

This will only work in outline mode, so an arch must specify
ARCH_DISABLE_KASAN_INLINE if it requires this.

Link: https://lkml.kernel.org/r/20210624034050.511391-3-dja@axtens.net


Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Suggested-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 158f2552

mm/kasan/common.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -331,6 +331,9 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, 
	u8 tag;

	u8 tag;

	void *tagged_object;

	void *tagged_object;





	if (!kasan_arch_is_ready())

		return false;



	tag = get_tag(object);

	tag = get_tag(object);

	tagged_object = object;

	tagged_object = object;

	object = kasan_reset_tag(object);

	object = kasan_reset_tag(object);

mm/kasan/generic.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -163,6 +163,9 @@ static __always_inline bool check_region_inline(unsigned long addr, 
						size_t size, bool write,

						size_t size, bool write,

						unsigned long ret_ip)

						unsigned long ret_ip)

{

{

	if (!kasan_arch_is_ready())

		return true;



	if (unlikely(size == 0))

	if (unlikely(size == 0))

		return true;

		return true;

mm/kasan/kasan.h

+6 −0
Original line number Original line Diff line number Diff line
@@ -449,6 +449,12 @@ static inline void kasan_poison_last_granule(const void *address, size_t size) { 




#endif /* CONFIG_KASAN_GENERIC */

#endif /* CONFIG_KASAN_GENERIC */





#ifndef kasan_arch_is_ready

static inline bool kasan_arch_is_ready(void)	{ return true; }

#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE)

#error kasan_arch_is_ready only works in KASAN generic outline mode!

#endif



/*

/*

 * Exported functions for interfaces called from assembly or from generated

 * Exported functions for interfaces called from assembly or from generated

 * code. Declarations here to avoid warning about missing declarations.

 * code. Declarations here to avoid warning about missing declarations.

mm/kasan/shadow.c

+6 −0
Original line number Original line Diff line number Diff line
@@ -73,6 +73,9 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) 
{

{

	void *shadow_start, *shadow_end;

	void *shadow_start, *shadow_end;





	if (!kasan_arch_is_ready())

		return;



	/*

	/*

	 * Perform shadow offset calculation based on untagged address, as

	 * Perform shadow offset calculation based on untagged address, as

	 * some of the callers (e.g. kasan_poison_object_data) pass tagged

	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
@@ -99,6 +102,9 @@ EXPORT_SYMBOL(kasan_poison); 
#ifdef CONFIG_KASAN_GENERIC

#ifdef CONFIG_KASAN_GENERIC

void kasan_poison_last_granule(const void *addr, size_t size)

void kasan_poison_last_granule(const void *addr, size_t size)

{

{

	if (!kasan_arch_is_ready())

		return;



	if (size & KASAN_GRANULE_MASK) {

	if (size & KASAN_GRANULE_MASK) {

		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);

		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);

		*shadow = size & KASAN_GRANULE_MASK;

		*shadow = size & KASAN_GRANULE_MASK;