net: hso: check for allocation failure in hso_create_bulk_serial_device()

In current kernels, small allocations never actually fail so this
patch shouldn't affect runtime.

Originally this error handling code written with the idea that if
the "serial->tiocmget" allocation failed, then we would continue
operating instead of bailing out early.  But in later years we added
an unchecked dereference on the next line.

	serial->tiocmget->serial_state_notification = kzalloc();
        ^^^^^^^^^^^^^^^^^^

Since these allocations are never going fail in real life, this is
mostly a philosophical debate, but I think bailing out early is the
correct behavior that the user would want.  And generally it's safer to
bail as soon an error happens.

Fixes: af0de130 ("usb: hso: obey DMA rules in tiocmget")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/hso.c

@@ -2618,13 +2618,13 @@ static struct hso_device *hso_create_bulk_serial_device(
 		num_urbs = 2;
 		serial->tiocmget = kzalloc(sizeof(struct hso_tiocmget),
 					   GFP_KERNEL);
+		if (!serial->tiocmget)
+			goto exit;
 		serial->tiocmget->serial_state_notification
 			= kzalloc(sizeof(struct hso_serial_state_notification),
 					   GFP_KERNEL);
-		/* it isn't going to break our heart if serial->tiocmget
-		 *  allocation fails don't bother checking this.
-		 */
-		if (serial->tiocmget && serial->tiocmget->serial_state_notification) {
+		if (!serial->tiocmget->serial_state_notification)
+			goto exit;
 		tiocmget = serial->tiocmget;
 		tiocmget->endp = hso_get_ep(interface,
 					    USB_ENDPOINT_XFER_INT,
@@ -2641,7 +2641,6 @@ static struct hso_device *hso_create_bulk_serial_device(
 		} else
 			hso_free_tiomget(serial);
 	}
-	}
 	else
 		num_urbs = 1;