Here are five possible code completions for the given function, addressing the CWE-476 (NULL Pointer Dereference) vulnerability:

1. Check for NULL pointers before dereferencing:

```c
if (!port_dev || !hdev || !hub) {
    return -EINVAL;
}
return sprintf(buf, "%d\n", port_dev->disable_autosuspend);
```

2. Use a ternary operator to handle potential NULL pointers:

```c
return (port_dev && hdev && hub) ? 
    sprintf(buf, "%d\n", port_dev->disable_autosuspend) : -EINVAL;
```

3. Implement error handling with goto statements:

```c
if (!port_dev) goto error;
if (!hdev) goto error;
if (!hub) goto error;
return sprintf(buf, "%d\n", port_dev->disable_autosuspend);

error:
    return -EINVAL;
```

4. Use a series of if statements with early returns:

```c
if (!port_dev) return -EINVAL;
if (!hdev) return -EINVAL;
if (!hub) return -EINVAL;
return sprintf(buf, "%d\n", port_dev->disable_autosuspend);
```

5. Implement a custom macro for NULL checks:

```c
#define CHECK_NULL(ptr) if (!ptr) return -EINVAL

CHECK_NULL(port_dev);
CHECK_NULL(hdev);
CHECK_NULL(hub);
return sprintf(buf, "%d\n", port_dev->disable_autosuspend);
```