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>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 4b2e10d5d641..9226b4d9118f 100644
--- 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);