Input: evdev - properly access RCU-protected 'grab' data

We should use rcu_dereference_protected() when checking if given client
is the one that grabbed the device. This fixes warnings produced by
sparse.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 4b2e10d..9226b4d 100644 (file)
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -180,7 +180,10 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
 
 static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
 {
-       if (evdev->grab != client)
+       struct evdev_client *grab = rcu_dereference_protected(evdev->grab,
+                                       lockdep_is_held(&evdev->mutex));
+
+       if (grab != client)
                return  -EINVAL;
 
        rcu_assign_pointer(evdev->grab, NULL);
@@ -259,8 +262,7 @@ static int evdev_release(struct inode *inode, struct file *file)
        struct evdev *evdev = client->evdev;
 
        mutex_lock(&evdev->mutex);
-       if (evdev->grab == client)
-               evdev_ungrab(evdev, client);
+       evdev_ungrab(evdev, client);
        mutex_unlock(&evdev->mutex);
 
        evdev_detach_client(evdev, client);