USB: serial: iuu_phoenix: fix NULL-deref at open

commit 90507d54 upstream.

Fix NULL-pointer dereference at open should the device lack a bulk-in or
bulk-out endpoint:

Unable to handle kernel NULL pointer dereference at virtual address 00000030
...
PC is at iuu_open+0x78/0x59c [iuu_phoenix]

Fixes: 07c3b1a1 ("USB: remove broken usb-serial num_endpoints
check")
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2: add this check to the existing
 usb_serial_driver::attach implementation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/iuu_phoenix.c

@@ -112,7 +112,12 @@ static int iuu_alloc_buf(struct iuu_private *priv)
 
 static int iuu_startup(struct usb_serial *serial)
 {
+	unsigned char num_ports = serial->num_ports;
 	struct iuu_private *priv;
+
+	if (serial->num_bulk_in < num_ports || serial->num_bulk_out < num_ports)
+		return -ENODEV;
+
 	priv = kzalloc(sizeof(struct iuu_private), GFP_KERNEL);
 	dbg("%s- priv allocation success", __func__);
 	if (!priv)