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

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

symbol_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, 8 insertions, 4 deletions

diff --git a/drivers/usb/serial/symbolserial.c b/drivers/usb/serial/symbolserial.c
index cb7e95f9fcbf..f25e54526843 100644
--- a/drivers/usb/serial/symbolserial.c
+++ b/drivers/usb/serial/symbolserial.c
@@ -179,20 +179,24 @@ static void symbol_unthrottle(struct tty_struct *tty)
         struct symbol_private *priv = usb_get_serial_data(port->serial);
         unsigned long flags;
         int result;
+        bool was_throttled;
 
         dbg("%s - port %d", __func__, port->number);
 
         spin_lock_irqsave(&priv->lock, flags);
         priv->throttled = false;
+        was_throttled = priv->actually_throttled;
         priv->actually_throttled = false;
         spin_unlock_irqrestore(&priv->lock, flags);
 
         priv->int_urb->dev = port->serial->dev;
-        result = usb_submit_urb(priv->int_urb, GFP_ATOMIC);
-        if (result)
-                dev_err(&port->dev,
-                        "%s - failed submitting read urb, error %d\n",
+        if (was_throttled) {
+                result = usb_submit_urb(priv->int_urb, GFP_ATOMIC);
+                if (result)
+                        dev_err(&port->dev,
+                                "%s - failed submitting read urb, error %d\n",
                                                         __func__, result);
+        }
 }
 
 static int symbol_startup(struct usb_serial *serial)