[PATCH 26/29] drivers, usb: convert dev_data.count from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:21:13Z

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 | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index 79a2d8f..81d76f3 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -27,6 +27,7 @@
#include <linux/mmu_context.h>
#include <linux/aio.h>
#include <linux/uio.h>
+#include <linux/refcount.h>

#include <linux/device.h>
#include <linux/moduleparam.h>
@@ -114,7 +115,7 @@ enum ep0_state {

struct dev_data {
spinlock_t lock;
- atomic_t count;
+ refcount_t count;
enum ep0_state state; /* P: lock */
struct usb_gadgetfs_event event [N_EVENT];
unsigned ev_next;
@@ -150,12 +151,12 @@ struct dev_data {

static inline void get_dev (struct dev_data *data)
{
- atomic_inc (&data->count);
+ refcount_inc (&data->count);
}

static void put_dev (struct dev_data *data)
{
- if (likely (!atomic_dec_and_test (&data->count)))
+ if (likely (!refcount_dec_and_test (&data->count)))
return;
/* needs no more cleanup */
BUG_ON (waitqueue_active (&data->wait));
@@ -170,7 +171,7 @@ static struct dev_data *dev_new (void)
if (!dev)
return NULL;
dev->state = STATE_DEV_DISABLED;
- atomic_set (&dev->count, 1);
+ refcount_set (&dev->count, 1);
spin_lock_init (&dev->lock);
INIT_LIST_HEAD (&dev->epfiles);
init_waitqueue_head (&dev->wait);
--
2.7.4

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