[PATCH] tty: fix NULL pointer issue when tty_port ops is not set

[Fabien Dessenne]

Unlike 'client_ops' which is initialized to 'default_client_ops', the
port operations 'ops' may be left to NULL.
Check the 'ops' value before checking the 'ops->x' value.

Signed-off-by: Fabien Dessenne <fabien.desse...@st.com>
---
 drivers/tty/tty_port.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 044c3cb..a9e12b3 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -325,7 +325,7 @@ static void tty_port_shutdown(struct tty_port *port, struct 
tty_struct *tty)
                if (tty && C_HUPCL(tty))
                        tty_port_lower_dtr_rts(port);
 
-               if (port->ops->shutdown)
+               if (port->ops && port->ops->shutdown)
                        port->ops->shutdown(port);
        }
 out:
@@ -398,7 +398,7 @@ EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
  */
 int tty_port_carrier_raised(struct tty_port *port)
 {
-       if (port->ops->carrier_raised == NULL)
+       if (!port->ops || !port->ops->carrier_raised)
                return 1;
        return port->ops->carrier_raised(port);
 }
@@ -414,7 +414,7 @@ EXPORT_SYMBOL(tty_port_carrier_raised);
  */
 void tty_port_raise_dtr_rts(struct tty_port *port)
 {
-       if (port->ops->dtr_rts)
+       if (port->ops && port->ops->dtr_rts)
                port->ops->dtr_rts(port, 1);
 }
 EXPORT_SYMBOL(tty_port_raise_dtr_rts);
@@ -429,7 +429,7 @@ EXPORT_SYMBOL(tty_port_raise_dtr_rts);
  */
 void tty_port_lower_dtr_rts(struct tty_port *port)
 {
-       if (port->ops->dtr_rts)
+       if (port->ops && port->ops->dtr_rts)
                port->ops->dtr_rts(port, 0);
 }
 EXPORT_SYMBOL(tty_port_lower_dtr_rts);
@@ -684,7 +684,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct 
*tty,
 
        if (!tty_port_initialized(port)) {
                clear_bit(TTY_IO_ERROR, &tty->flags);
-               if (port->ops->activate) {
+               if (port->ops && port->ops->activate) {
                        int retval = port->ops->activate(port, tty);
                        if (retval) {
                                mutex_unlock(&port->mutex);
-- 
2.7.4