kasan: add return value for kasan_mempool_poison_object

Add a return value for kasan_mempool_poison_object that lets the caller
know whether the allocation is affected by a double-free or an
invalid-free bug.  The caller can use this return value to stop operating
on the object.

Also introduce a check_page_allocation helper function to improve the code
readability.

Link: https://lkml.kernel.org/r/618af65273875fb9f56954285443279b15f1fcd9.1703024586.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/kasan.h

@@ -212,7 +212,7 @@ static __always_inline void * __must_check kasan_krealloc(const void *object,
 	return (void *)object;
 }
 
-void __kasan_mempool_poison_object(void *ptr, unsigned long ip);
+bool __kasan_mempool_poison_object(void *ptr, unsigned long ip);
 /**
  * kasan_mempool_poison_object - Check and poison a mempool slab allocation.
  * @ptr: Pointer to the slab allocation.
@@ -225,16 +225,20 @@ void __kasan_mempool_poison_object(void *ptr, unsigned long ip);
  * without putting it into the quarantine (for the Generic mode).
  *
  * This function also performs checks to detect double-free and invalid-free
- * bugs and reports them.
+ * bugs and reports them. The caller can use the return value of this function
+ * to find out if the allocation is buggy.
  *
  * This function operates on all slab allocations including large kmalloc
  * allocations (the ones returned by kmalloc_large() or by kmalloc() with the
  * size > KMALLOC_MAX_SIZE).
+ *
+ * Return: true if the allocation can be safely reused; false otherwise.
  */
-static __always_inline void kasan_mempool_poison_object(void *ptr)
+static __always_inline bool kasan_mempool_poison_object(void *ptr)
 {
 	if (kasan_enabled())
-		__kasan_mempool_poison_object(ptr, _RET_IP_);
+		return __kasan_mempool_poison_object(ptr, _RET_IP_);
+	return true;
 }
 
 /*
@@ -293,7 +297,10 @@ static inline void *kasan_krealloc(const void *object, size_t new_size,
 {
 	return (void *)object;
 }
-static inline void kasan_mempool_poison_object(void *ptr) {}
+static inline bool kasan_mempool_poison_object(void *ptr)
+{
+	return true;
+}
 static inline bool kasan_check_byte(const void *address)
 {
 	return true;

mm/kasan/common.c

@@ -254,7 +254,7 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 	return ____kasan_slab_free(cache, object, ip, true, init);
 }
 
-static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)
+static inline bool check_page_allocation(void *ptr, unsigned long ip)
 {
 	if (!kasan_arch_is_ready())
 		return false;
@@ -269,17 +269,14 @@ static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)
 		return true;
 	}
 
-	/*
-	 * The object will be poisoned by kasan_poison_pages() or
-	 * kasan_mempool_poison_object().
-	 */
-
 	return false;
 }
 
 void __kasan_kfree_large(void *ptr, unsigned long ip)
 {
-	____kasan_kfree_large(ptr, ip);
+	check_page_allocation(ptr, ip);
+
+	/* The object will be poisoned by kasan_poison_pages(). */
 }
 
 void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
@@ -429,7 +426,7 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag
 		return ____kasan_kmalloc(slab->slab_cache, object, size, flags);
 }
 
-void __kasan_mempool_poison_object(void *ptr, unsigned long ip)
+bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
 {
 	struct folio *folio;
 
@@ -442,13 +439,15 @@ void __kasan_mempool_poison_object(void *ptr, unsigned long ip)
 	 * KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
 	 */
 	if (unlikely(!folio_test_slab(folio))) {
-		if (____kasan_kfree_large(ptr, ip))
+		if (check_page_allocation(ptr, ip))
-			return;
+			return false;
 		kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
+		return true;
 	} else {
 		struct slab *slab = folio_slab(folio);
 
-		____kasan_slab_free(slab->slab_cache, ptr, ip, false, false);
+		return !____kasan_slab_free(slab->slab_cache, ptr, ip,
+						false, false);
 	}
 }