[mm,v10,12/42] kasan: hide invalid free check implementation

Commit Message

Andrey Konovalov Nov. 13, 2020, 10:15 p.m. UTC

This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

For software KASAN modes the check is based on the value in the shadow
memory. Hardware tag-based KASAN won't be using shadow, so hide the
implementation of the check in check_invalid_free().

Also simplify the code for software tag-based mode.

No functional changes for software modes.

Signed-off-by: Andrey Konovalov <[e-mail]>
Signed-off-by: Vincenzo Frascino <[e-mail]>
Reviewed-by: Marco Elver <[e-mail]>
Reviewed-by: Alexander Potapenko <[e-mail]>
---
Change-Id: I5fae9531c9fc948eb4d4e0c589744032fc5a0789
---
 mm/kasan/common.c  | 19 +------------------
 mm/kasan/generic.c |  7 +++++++
 mm/kasan/kasan.h   |  2 ++
 mm/kasan/sw_tags.c |  9 +++++++++
 4 files changed, 19 insertions(+), 18 deletions(-)

Patch

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index b3ebee6fcfca..ae55570b4d32 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -278,25 +278,9 @@  void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
 	return (void *)object;
 }
 
-static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
-{
-	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
-		return shadow_byte < 0 ||
-			shadow_byte >= KASAN_GRANULE_SIZE;
-
-	/* else CONFIG_KASAN_SW_TAGS: */
-	if ((u8)shadow_byte == KASAN_TAG_INVALID)
-		return true;
-	if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte))
-		return true;
-
-	return false;
-}
-
 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 			      unsigned long ip, bool quarantine)
 {
-	s8 shadow_byte;
 	u8 tag;
 	void *tagged_object;
 	unsigned long rounded_up_size;
@@ -318,8 +302,7 @@  static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 		return false;
 
-	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
-	if (shadow_invalid(tag, shadow_byte)) {
+	if (check_invalid_free(tagged_object)) {
 		kasan_report_invalid_free(tagged_object, ip);
 		return true;
 	}
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 754217c258a8..67642acafe92 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -188,6 +188,13 @@  bool check_memory_region(unsigned long addr, size_t size, bool write,
 	return check_memory_region_inline(addr, size, write, ret_ip);
 }
 
+bool check_invalid_free(void *addr)
+{
+	s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
+
+	return shadow_byte < 0 || shadow_byte >= KASAN_GRANULE_SIZE;
+}
+
 void kasan_cache_shrink(struct kmem_cache *cache)
 {
 	quarantine_remove_cache(cache);
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index eec88bf28c64..e5b5f60bc963 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -166,6 +166,8 @@  void unpoison_range(const void *address, size_t size);
 bool check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip);
 
+bool check_invalid_free(void *addr);
+
 void *find_first_bad_addr(void *addr, size_t size);
 const char *get_bug_type(struct kasan_access_info *info);
 
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index c0b3f327812b..64540109c461 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -121,6 +121,15 @@  bool check_memory_region(unsigned long addr, size_t size, bool write,
 	return true;
 }
 
+bool check_invalid_free(void *addr)
+{
+	u8 tag = get_tag(addr);
+	u8 shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(reset_tag(addr)));
+
+	return (shadow_byte == KASAN_TAG_INVALID) ||
+		(tag != KASAN_TAG_KERNEL && tag != shadow_byte);
+}
+
 #define DEFINE_HWASAN_LOAD_STORE(size)					\
 	void __hwasan_load##size##_noabort(unsigned long addr)		\
 	{								\