USB: serial: cyberjack: fix write-URB completion race

The write-URB busy flag was being cleared before the completion handler
was done with the URB, something which could lead to corrupt transfers
due to a racing write request if the URB is resubmitted.

Fixes: 507ca9bc0476 ("[PATCH] USB: add ability for usb-serial drivers to determine if their write urb is currently being used.")
Cc: stable <stable@vger.kernel.org>     # 2.6.13
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/cyberjack.c b/drivers/usb/serial/cyberjack.c
index 8219706..2e40908 100644 (file)
--- a/drivers/usb/serial/cyberjack.c
+++ b/drivers/usb/serial/cyberjack.c
@@ -357,11 +357,12 @@ static void cyberjack_write_bulk_callback(struct urb *urb)
        struct device *dev = &port->dev;
        int status = urb->status;
        unsigned long flags;
+       bool resubmitted = false;
 
-       set_bit(0, &port->write_urbs_free);
        if (status) {
                dev_dbg(dev, "%s - nonzero write bulk status received: %d\n",
                        __func__, status);
+               set_bit(0, &port->write_urbs_free);
                return;
        }
 
@@ -394,6 +395,8 @@ static void cyberjack_write_bulk_callback(struct urb *urb)
                        goto exit;
                }
 
+               resubmitted = true;
+
                dev_dbg(dev, "%s - priv->wrsent=%d\n", __func__, priv->wrsent);
                dev_dbg(dev, "%s - priv->wrfilled=%d\n", __func__, priv->wrfilled);
 
@@ -410,6 +413,8 @@ static void cyberjack_write_bulk_callback(struct urb *urb)
 
 exit:
        spin_unlock_irqrestore(&priv->lock, flags);
+       if (!resubmitted)
+               set_bit(0, &port->write_urbs_free);
        usb_serial_port_softint(port);
 }