[PATCH 5/5] USB: serial: quatech2: handle unbound ports

[Johan Hovold <johan@kernel.org>]

Check for NULL port data in the event handlers to avoid dereferencing a
NULL pointer in the unlikely case where a port device isn't bound to a
driver (e.g. after an allocation failure on port probe).

Fixes: f7a33e608d9a ("USB: serial: add quatech2 usb to serial driver")
Cc: stable <stable@vger.kernel.org>     # 3.5
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/quatech2.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c
index a62981ca7a73..c76a2c0c32ff 100644
--- a/drivers/usb/serial/quatech2.c
+++ b/drivers/usb/serial/quatech2.c
@@ -470,6 +470,13 @@ static int get_serial_info(struct tty_struct *tty,
 
 static void qt2_process_status(struct usb_serial_port *port, unsigned char *ch)
 {
+	struct qt2_port_private *port_priv;
+
+	/* May be called from qt2_process_read_urb() for an unbound port. */
+	port_priv = usb_get_serial_port_data(port);
+	if (!port_priv)
+		return;
+
 	switch (*ch) {
 	case QT2_LINE_STATUS:
 		qt2_update_lsr(port, ch + 1);
@@ -484,14 +491,27 @@ static void qt2_process_status(struct usb_serial_port *port, unsigned char *ch)
 static void qt2_process_xmit_empty(struct usb_serial_port *port,
 				   unsigned char *ch)
 {
+	struct qt2_port_private *port_priv;
 	int bytes_written;
 
+	/* May be called from qt2_process_read_urb() for an unbound port. */
+	port_priv = usb_get_serial_port_data(port);
+	if (!port_priv)
+		return;
+
 	bytes_written = (int)(*ch) + (int)(*(ch + 1) << 4);
 }
 
 /* not needed, kept to document functionality */
 static void qt2_process_flush(struct usb_serial_port *port, unsigned char *ch)
 {
+	struct qt2_port_private *port_priv;
+
+	/* May be called from qt2_process_read_urb() for an unbound port. */
+	port_priv = usb_get_serial_port_data(port);
+	if (!port_priv)
+		return;
+
 	return;
 }
 
-- 
2.24.1