USB: serial: fix race between unthrottle and completion handler in visor

usb:usbserial:visor: fix race between unthrottle and completion handler

visor_unthrottle() mustn't resubmit the URB unconditionally
as the URB may still be running.

the same bug as opticon.

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/usb/serial/visor.c b/drivers/usb/serial/visor.c
index b9341f0e452b..ad1f9232292d 100644
--- a/drivers/usb/serial/visor.c
+++ b/drivers/usb/serial/visor.c
@@ -595,20 +595,23 @@ static void visor_unthrottle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
         struct visor_private *priv = usb_get_serial_port_data(port);
-        int result;
+        int result, was_throttled;
 
         dbg("%s - port %d", __func__, port->number);
         spin_lock_irq(&priv->lock);
         priv->throttled = 0;
+        was_throttled = priv->actually_throttled;
         priv->actually_throttled = 0;
         spin_unlock_irq(&priv->lock);
 
-        port->read_urb->dev = port->serial->dev;
-        result = usb_submit_urb(port->read_urb, GFP_KERNEL);
-        if (result)
-                dev_err(&port->dev,
-                        "%s - failed submitting read urb, error %d\n",
+        if (was_throttled) {
+                port->read_urb->dev = port->serial->dev;
+                result = usb_submit_urb(port->read_urb, GFP_KERNEL);
+                if (result)
+                        dev_err(&port->dev,
+                                "%s - failed submitting read urb, error %d\n",
                                                         __func__, result);
+        }
 }
 
 static int palm_os_3_probe(struct usb_serial *serial,