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>

1 files changed, 12 insertions, 5 deletions

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index bbf6e2fa4ffd..33387e254caa 100644
--- a/include/linux/kasan.h
+++ b/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;