[PATCH 4.4 041/101] USB: serial: kobil_sct: fix NULL-deref in write

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@xxxxxxxxxx>

commit 21ce57840243c7b70fbc1ebd3dceeb70bb6e9e09 upstream.

Fix NULL-pointer dereference in write() should the device lack the
expected interrupt-out endpoint:

Unable to handle kernel NULL pointer dereference at virtual address 00000054
...
PC is at kobil_write+0x144/0x2a0 [kobil_sct]

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/serial/kobil_sct.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/usb/serial/kobil_sct.c
+++ b/drivers/usb/serial/kobil_sct.c
@@ -51,6 +51,7 @@
 
 
 /* Function prototypes */
+static int kobil_attach(struct usb_serial *serial);
 static int kobil_port_probe(struct usb_serial_port *probe);
 static int kobil_port_remove(struct usb_serial_port *probe);
 static int  kobil_open(struct tty_struct *tty, struct usb_serial_port *port);
@@ -86,6 +87,7 @@ static struct usb_serial_driver kobil_de
 	.description =		"KOBIL USB smart card terminal",
 	.id_table =		id_table,
 	.num_ports =		1,
+	.attach =		kobil_attach,
 	.port_probe =		kobil_port_probe,
 	.port_remove =		kobil_port_remove,
 	.ioctl =		kobil_ioctl,
@@ -113,6 +115,16 @@ struct kobil_private {
 };
 
 
+static int kobil_attach(struct usb_serial *serial)
+{
+	if (serial->num_interrupt_out < serial->num_ports) {
+		dev_err(&serial->interface->dev, "missing interrupt-out endpoint\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 static int kobil_port_probe(struct usb_serial_port *port)
 {
 	struct usb_serial *serial = port->serial;