drivers, connector: convert cn_callback_entry.refcnt from atomic_t to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable cn_callback_entry.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/connector.h b/include/linux/connector.h
index f8fe863..032102b 100644
--- a/include/linux/connector.h
+++ b/include/linux/connector.h
@@ -22,7 +22,7 @@
#define __CONNECTOR_H
-#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/list.h>
#include <linux/workqueue.h>
@@ -49,7 +49,7 @@ struct cn_callback_id {
struct cn_callback_entry {
struct list_head callback_entry;
- atomic_t refcnt;
+ refcount_t refcnt;
struct cn_queue_dev *pdev;
struct cn_callback_id id;