[PATCH 3.12 50/98] USB: mct_u232: add sanity checking in probe

[Jiri Slaby]

From: Oliver Neukum <oneukum@xxxxxxxx>

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

===============

commit 4e9a0b05257f29cf4b75f3209243ed71614d062e upstream.

An attack using the lack of sanity checking in probe is known. This
patch checks for the existence of a second port.

CVE-2016-3136

Signed-off-by: Oliver Neukum <ONeukum@xxxxxxxx>
[johan: add error message ]
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/usb/serial/mct_u232.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 6a15adf53360..c14c29ff1151 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -377,14 +377,21 @@ static void mct_u232_msr_to_state(struct usb_serial_port *port,
 
 static int mct_u232_port_probe(struct usb_serial_port *port)
 {
+	struct usb_serial *serial = port->serial;
 	struct mct_u232_private *priv;
 
+	/* check first to simplify error handling */
+	if (!serial->port[1] || !serial->port[1]->interrupt_in_urb) {
+		dev_err(&port->dev, "expected endpoint missing\n");
+		return -ENODEV;
+	}
+
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
 	/* Use second interrupt-in endpoint for reading. */
-	priv->read_urb = port->serial->port[1]->interrupt_in_urb;
+	priv->read_urb = serial->port[1]->interrupt_in_urb;
 	priv->read_urb->context = port;
 
 	spin_lock_init(&priv->lock);
-- 
2.8.1