USB: serial: mos7840: fix NULL-deref at open

Fix NULL-pointer dereference in open() should the device lack the
expected endpoints:

Unable to handle kernel NULL pointer dereference at virtual address 00000030
...
PC is at mos7840_open+0x88/0x8dc [mos7840]

Note that we continue to treat the interrupt-in endpoint as optional for
now.

Fixes: 3f5429746d91 ("USB: Moschip 7840 USB-Serial Driver")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 9a220b8e810f161be985d9655ec6d9dee90147dc..bb933c6321e5d8dca139f83ce912abefec3e4dbc 100644 (file)
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -2113,6 +2113,17 @@ static int mos7840_calc_num_ports(struct usb_serial *serial)
        return mos7840_num_ports;
 }
 
+static int mos7840_attach(struct usb_serial *serial)
+{
+       if (serial->num_bulk_in < serial->num_ports ||
+                       serial->num_bulk_out < serial->num_ports) {
+               dev_err(&serial->interface->dev, "missing endpoints\n");
+               return -ENODEV;
+       }
+
+       return 0;
+}
+
 static int mos7840_port_probe(struct usb_serial_port *port)
 {
        struct usb_serial *serial = port->serial;
@@ -2388,6 +2399,7 @@ static struct usb_serial_driver moschip7840_4port_device = {
        .tiocmset = mos7840_tiocmset,
        .tiocmiwait = usb_serial_generic_tiocmiwait,
        .get_icount = usb_serial_generic_get_icount,
+       .attach = mos7840_attach,
        .port_probe = mos7840_port_probe,
        .port_remove = mos7840_port_remove,
        .read_bulk_callback = mos7840_bulk_in_callback,