[PATCH 04/29] drivers, connector: convert cn_callback_entry.refcnt from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:20:51Z

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
drivers/connector/cn_queue.c | 4 ++--
drivers/connector/connector.c | 2 +-
include/linux/connector.h | 4 ++--
3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/connector/cn_queue.c b/drivers/connector/cn_queue.c
index 1f8bf05..9c54fdf 100644
--- a/drivers/connector/cn_queue.c
+++ b/drivers/connector/cn_queue.c
@@ -45,7 +45,7 @@ cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,
return NULL;
}

- atomic_set(&cbq->refcnt, 1);
+ refcount_set(&cbq->refcnt, 1);

atomic_inc(&dev->refcnt);
cbq->pdev = dev;
@@ -58,7 +58,7 @@ cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,

void cn_queue_release_callback(struct cn_callback_entry *cbq)
{
- if (!atomic_dec_and_test(&cbq->refcnt))
+ if (!refcount_dec_and_test(&cbq->refcnt))
return;

atomic_dec(&cbq->pdev->refcnt);
diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
index 25693b0..8615594b 100644
--- a/drivers/connector/connector.c
+++ b/drivers/connector/connector.c
@@ -157,7 +157,7 @@ static int cn_call_callback(struct sk_buff *skb)
spin_lock_bh(&dev->cbdev->queue_lock);
list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
if (cn_cb_equal(&i->id.id, &msg->id)) {
- atomic_inc(&i->refcnt);
+ refcount_inc(&i->refcnt);
cbq = i;
break;
}
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;
--
2.7.4