USB: serial: omninet: fix NULL-derefs at open and disconnect

commit a5bc0194 upstream.

Fix NULL-pointer dereferences at open() and disconnect() should the
device lack the expected bulk-out endpoints:

Unable to handle kernel NULL pointer dereference at virtual address 000000b4
...
[c0170ff0>] (__lock_acquire) from [<c0172f00>] (lock_acquire+0x108/0x264)
[<c0172f00>] (lock_acquire) from [<c06a5090>] (_raw_spin_lock_irqsave+0x58/0x6c)
[<c06a5090>] (_raw_spin_lock_irqsave) from [<c0470684>] (tty_port_tty_set+0x28/0xa4)
[<c0470684>] (tty_port_tty_set) from [<bf08d384>] (omninet_open+0x30/0x40 [omninet])
[<bf08d384>] (omninet_open [omninet]) from [<bf07c118>] (serial_port_activate+0x68/0x98 [usbserial])

Unable to handle kernel NULL pointer dereference at virtual address 00000234
...
[<bf01f418>] (omninet_disconnect [omninet]) from [<bf0016c0>] (usb_serial_disconnect+0xe4/0x100 [usbserial])

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
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/omninet.c

@@ -152,6 +152,12 @@ static int omninet_attach(struct usb_serial *serial)
 	struct omninet_data *od;
 	struct usb_serial_port *port = serial->port[0];
 
+	/* The second bulk-out endpoint is used for writing. */
+	if (serial->num_bulk_out < 2) {
+		dev_err(&serial->interface->dev, "missing endpoints\n");
+		return -ENODEV;
+	}
+
 	od = kmalloc(sizeof(struct omninet_data), GFP_KERNEL);
 	if (!od) {
 		dev_err(&port->dev, "%s- kmalloc(%Zd) failed.\n",