[PATCH 27/29] drivers, usb: convert ep_data.count from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:21:14Z

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/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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