[media] uvcvideo: Fix race of open and suspend in error case

Ming Lei reported:
IMO, there is a minor fault in the error handling path of
uvc_status_start() inside uvc_v4l2_open(), and the 'users' count should
have been decreased before usb_autopm_put_interface(). In theory, a [URB
resubmission] warning can be triggered when the device is opened just
between usb_autopm_put_interface() and atomic_dec(&stream->dev->users).
The fix is trivial.

Reported-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 97a4ffd..b2dc326 100644 (file)
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -501,8 +501,8 @@ static int uvc_v4l2_open(struct file *file)
        if (atomic_inc_return(&stream->dev->users) == 1) {
                ret = uvc_status_start(stream->dev);
                if (ret < 0) {
-                       usb_autopm_put_interface(stream->dev->intf);
                        atomic_dec(&stream->dev->users);
+                       usb_autopm_put_interface(stream->dev->intf);
                        kfree(handle);
                        return ret;
                }