[PATCH v3 mm 05/13] kasan: unify large kfree checks

Andrey Konovalov
2021-02-05T17:42:29Z

Unify checks in kasan_kfree_large() and in kasan_slab_free_mempool()
for large allocations as it's done for small kfree() allocations.

With this change, kasan_slab_free_mempool() starts checking that the
first byte of the memory that's being freed is accessible.

Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
include/linux/kasan.h | 16 ++++++++--------
mm/kasan/common.c | 36 ++++++++++++++++++++++++++----------
2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index e6ed969e74b3..14f72ec96492 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -200,6 +200,13 @@ static __always_inline bool kasan_slab_free(struct kmem_cache *s, void *object)
return false;
}

+void __kasan_kfree_large(void *ptr, unsigned long ip);
+static __always_inline void kasan_kfree_large(void *ptr)
+{
+ if (kasan_enabled())
+ __kasan_kfree_large(ptr, _RET_IP_);
+}
+
void __kasan_slab_free_mempool(void *ptr, unsigned long ip);
static __always_inline void kasan_slab_free_mempool(void *ptr)
{
@@ -247,13 +254,6 @@ static __always_inline void * __must_check kasan_krealloc(const void *object,
return (void *)object;
}

-void __kasan_kfree_large(void *ptr, unsigned long ip);
-static __always_inline void kasan_kfree_large(void *ptr)
-{
- if (kasan_enabled())
- __kasan_kfree_large(ptr, _RET_IP_);
-}
-
/*
* Unlike kasan_check_read/write(), kasan_check_byte() is performed even for
* the hardware tag-based mode that doesn't rely on compiler instrumentation.
@@ -302,6 +302,7 @@ static inline bool kasan_slab_free(struct kmem_cache *s, void *object)
{
return false;
}
+static inline void kasan_kfree_large(void *ptr) {}
static inline void kasan_slab_free_mempool(void *ptr) {}
static inline void *kasan_slab_alloc(struct kmem_cache *s, void *object,
gfp_t flags)
@@ -322,7 +323,6 @@ static inline void *kasan_krealloc(const void *object, size_t new_size,
{
return (void *)object;
}
-static inline void kasan_kfree_large(void *ptr) {}
static inline bool kasan_check_byte(const void *address)
{
return true;
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index da24b144d46c..7ea643f7e69c 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -364,6 +364,31 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
return ____kasan_slab_free(cache, object, ip, true);
}

+static bool ____kasan_kfree_large(void *ptr, unsigned long ip)
+{
+ if (ptr != page_address(virt_to_head_page(ptr))) {
+ kasan_report_invalid_free(ptr, ip);
+ return true;
+ }
+
+ if (!kasan_byte_accessible(ptr)) {
+ kasan_report_invalid_free(ptr, ip);
+ return true;
+ }
+
+ /*
+ * The object will be poisoned by kasan_free_pages() or
+ * kasan_slab_free_mempool().
+ */
+
+ return false;
+}
+
+void __kasan_kfree_large(void *ptr, unsigned long ip)
+{
+ ____kasan_kfree_large(ptr, ip);
+}
+
void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
{
struct page *page;
@@ -377,10 +402,8 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
* KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
*/
if (unlikely(!PageSlab(page))) {
- if (ptr != page_address(page)) {
- kasan_report_invalid_free(ptr, ip);
+ if (____kasan_kfree_large(ptr, ip))
return;
- }
kasan_poison(ptr, page_size(page), KASAN_FREE_PAGE);
} else {
____kasan_slab_free(page->slab_cache, ptr, ip, false);
@@ -539,13 +562,6 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag
return ____kasan_kmalloc(page->slab_cache, object, size, flags);
}

-void __kasan_kfree_large(void *ptr, unsigned long ip)
-{
- if (ptr != page_address(virt_to_head_page(ptr)))
- kasan_report_invalid_free(ptr, ip);
- /* The object will be poisoned by kasan_free_pages(). */
-}
-
bool __kasan_check_byte(const void *address, unsigned long ip)
{
if (!kasan_byte_accessible(address)) {
--
2.30.0.365.g02bc693789-goog