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

[Elena Reshetova <elena.reshetova@xxxxxxxxx>]

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@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
 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


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