USB: serial: fix USB serial fix kfifo_len locking

This patch fix a possible race bug in drivers/usb/serial/generic with
the new kfifo API.

Please apply it to the 2.6.33-rc* tree.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index f1ea3a3..5ce033a 100644 (file)
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -386,12 +386,12 @@ int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
 
        dbg("%s - port %d", __func__, port->number);
 
-       if (serial->type->max_in_flight_urbs) {
-               spin_lock_irqsave(&port->lock, flags);
+       spin_lock_irqsave(&port->lock, flags);
+       if (serial->type->max_in_flight_urbs)
                chars = port->tx_bytes_flight;
-               spin_unlock_irqrestore(&port->lock, flags);
-       } else if (serial->num_bulk_out)
+       else if (serial->num_bulk_out)
                chars = kfifo_len(&port->write_fifo);
+       spin_unlock_irqrestore(&port->lock, flags);
 
        dbg("%s - returns %d", __func__, chars);
        return chars;