HID: hiddev: fix potential use-after-free

Commit 6cb4b040795 ("HID: hiddev: fix race between hiddev_disconnect
and hiddev_release") made it possible to access hiddev (for unlocking
the existance mutex) once hiddev has been kfreed.

Change the order so that this can not happen (always unlock the mutex first,
it is needed only to protect access to ->exist and ->open).

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index ff3c644888b1..4985f485932f 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -923,10 +923,11 @@ void hiddev_disconnect(struct hid_device *hid)
         usb_deregister_dev(usbhid->intf, &hiddev_class);
 
         if (hiddev->open) {
+                mutex_unlock(&hiddev->existancelock);
                 usbhid_close(hiddev->hid);
                 wake_up_interruptible(&hiddev->wait);
         } else {
+                mutex_unlock(&hiddev->existancelock);
                 kfree(hiddev);
         }
-        mutex_unlock(&hiddev->existancelock);
 }