USB: serial: fix null-pointer dereferences on disconnect
Make sure serial-driver dtr_rts is called with disc_mutex held after
checking the disconnected flag.
Due to a bug in the tty layer, dtr_rts may get called after a device has
been disconnected and the tty-device unregistered. Some drivers have had
individual checks for disconnect to make sure the disconnected interface
was not accessed, but this should really be handled in usb-serial core
(at least until the long-standing tty-bug has been fixed).
Note that the problem has been made more acute with commit 0998d0631001
("device-core: Ensure drvdata = NULL when no driver is bound") as the
port data is now also NULL when dtr_rts is called resulting in further
oopses.
Reported-by: Chris Ruehl <chris.ruehl@gtsys.com.hk>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index b691175..d9c8651 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -499,19 +499,15 @@
unsigned int control_state;
struct mct_u232_private *priv = usb_get_serial_port_data(port);
- mutex_lock(&port->serial->disc_mutex);
- if (!port->serial->disconnected) {
- /* drop DTR and RTS */
- spin_lock_irq(&priv->lock);
- if (on)
- priv->control_state |= TIOCM_DTR | TIOCM_RTS;
- else
- priv->control_state &= ~(TIOCM_DTR | TIOCM_RTS);
- control_state = priv->control_state;
- spin_unlock_irq(&priv->lock);
- mct_u232_set_modem_ctrl(port, control_state);
- }
- mutex_unlock(&port->serial->disc_mutex);
+ spin_lock_irq(&priv->lock);
+ if (on)
+ priv->control_state |= TIOCM_DTR | TIOCM_RTS;
+ else
+ priv->control_state &= ~(TIOCM_DTR | TIOCM_RTS);
+ control_state = priv->control_state;
+ spin_unlock_irq(&priv->lock);
+
+ mct_u232_set_modem_ctrl(port, control_state);
}
static void mct_u232_close(struct usb_serial_port *port)