USB: ftdi_sio: Fix locking for change_speed() function

The change_speed() function should be serialized against multiple calls.
Use the cfg_lock mutex to do this.

Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 6fc09dc3b53e..1d7c4fac02e8 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -91,7 +91,7 @@ struct ftdi_private {
         unsigned long tx_outstanding_bytes;
         unsigned long tx_outstanding_urbs;
         unsigned short max_packet_size;
-        struct mutex cfg_lock; /* Avoid mess by parallel calls of config ioctl() */
+        struct mutex cfg_lock; /* Avoid mess by parallel calls of config ioctl() and change_speed() */
 };
 
 /* struct ftdi_sio_quirk is used by devices requiring special attention. */
@@ -1273,8 +1273,8 @@ check_and_exit:
              (priv->flags & ASYNC_SPD_MASK)) ||
             (((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST) &&
              (old_priv.custom_divisor != priv->custom_divisor))) {
-                mutex_unlock(&priv->cfg_lock);
                 change_speed(tty, port);
+                mutex_unlock(&priv->cfg_lock);
         }
         else
                 mutex_unlock(&priv->cfg_lock);
@@ -2265,9 +2265,11 @@ static void ftdi_set_termios(struct tty_struct *tty,
                 clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
         } else {
                 /* set the baudrate determined before */
+                mutex_lock(&priv->cfg_lock);
                 if (change_speed(tty, port))
                         dev_err(&port->dev, "%s urb failed to set baudrate\n",
                                 __func__);
+                mutex_unlock(&priv->cfg_lock);
                 /* Ensure RTS and DTR are raised when baudrate changed from 0 */
                 if (!old_termios || (old_termios->c_cflag & CBAUD) == B0)
                         set_mctrl(port, TIOCM_DTR | TIOCM_RTS);