[Xen-devel] [PATCH 27/29] drivers, usb: convert ep_data.count 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/usb/gadget/legacy/inode.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c 
b/drivers/usb/gadget/legacy/inode.c
index 81d76f3..d21a5f8 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -191,7 +191,7 @@ enum ep_state {
 struct ep_data {
        struct mutex                    lock;
        enum ep_state                   state;
-       atomic_t                        count;
+       refcount_t                      count;
        struct dev_data                 *dev;
        /* must hold dev->lock before accessing ep or req */
        struct usb_ep                   *ep;
@@ -206,12 +206,12 @@ struct ep_data {
 
 static inline void get_ep (struct ep_data *data)
 {
-       atomic_inc (&data->count);
+       refcount_inc (&data->count);
 }
 
 static void put_ep (struct ep_data *data)
 {
-       if (likely (!atomic_dec_and_test (&data->count)))
+       if (likely (!refcount_dec_and_test (&data->count)))
                return;
        put_dev (data->dev);
        /* needs no more cleanup */
@@ -1562,7 +1562,7 @@ static int activate_ep_files (struct dev_data *dev)
                init_waitqueue_head (&data->wait);
 
                strncpy (data->name, ep->name, sizeof (data->name) - 1);
-               atomic_set (&data->count, 1);
+               refcount_set (&data->count, 1);
                data->dev = dev;
                get_dev (dev);
 
-- 
2.7.4


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