kasan: unify large kfree checks

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.

Link: https://lkml.kernel.org/r/14ffc4cd867e0b1ed58f7527e3b748a1b4ad08aa.1612546384.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Reviewed-by: Marco Elver <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Branislav Rankov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Evgenii Stepanov <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Peter Collingbourne <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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;

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)) {