[PATCH AUTOSEL 4.4 17/21] tty: fix NULL pointer issue when tty_port ops is not set

[Sasha Levin <sashal@kernel.org>]

From: Fabien Dessenne <fabien.dessenne@st.com>

[ Upstream commit f4e68d58cf2b20a581759bbc7228052534652673 ]

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.dessenne@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
---
 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 482f33f20043..3f0ef1a4f558 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -212,7 +212,7 @@ 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:
@@ -292,7 +292,7 @@ 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);
 }
@@ -309,7 +309,7 @@ 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);
@@ -325,7 +325,7 @@ 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);
@@ -584,7 +584,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
 
 	if (!test_bit(ASYNCB_INITIALIZED, &port->flags)) {
 		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);
-- 
2.19.1