[PATCH 3/4][CVE-2016-3140] USB: digi_acceleport: do sanity checking for the number of ports

[Luis Henriques]

From: Oliver Neukum <oneukum at suse.com>

commit 5a07975ad0a36708c6b0a5b9fea1ff811d0b0c1f upstream.

The driver can be crashed with devices that expose crafted descriptors
with too few endpoints.

See: http://seclists.org/bugtraq/2016/Mar/61

Signed-off-by: Oliver Neukum <ONeukum at suse.com>
[johan: fix OOB endpoint check and add error messages ]
Signed-off-by: Johan Hovold <johan at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>

CVE-2016-3140
BugLink: https://bugs.launchpad.net/bugs/1556888
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/digi_acceleport.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 8a23c53b946e..cd6df875163e 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1252,8 +1252,27 @@ static int digi_port_init(struct usb_serial_port *port, unsigned port_num)
 
 static int digi_startup(struct usb_serial *serial)
 {
+	struct device *dev = &serial->interface->dev;
 	struct digi_serial *serial_priv;
 	int ret;
+	int i;
+
+	/* check whether the device has the expected number of endpoints */
+	if (serial->num_port_pointers < serial->type->num_ports + 1) {
+		dev_err(dev, "OOB endpoints missing\n");
+		return -ENODEV;
+	}
+
+	for (i = 0; i < serial->type->num_ports + 1 ; i++) {
+		if (!serial->port[i]->read_urb) {
+			dev_err(dev, "bulk-in endpoint missing\n");
+			return -ENODEV;
+		}
+		if (!serial->port[i]->write_urb) {
+			dev_err(dev, "bulk-out endpoint missing\n");
+			return -ENODEV;
+		}
+	}
 
 	serial_priv = kzalloc(sizeof(*serial_priv), GFP_KERNEL);
 	if (!serial_priv)