Here are five possible code completions for the given function, addressing the CWE-401  vulnerability:

1. Simple deallocation:
```c
    for (i = 0; i < nvdev->num_chn; i++)
        kfree(nvdev->chan_table[i]);
    kfree(nvdev->chan_table);
    kfree(nvdev);
```

2. Nullifying pointers after freeing:
```c
    for (i = 0; i < nvdev->num_chn; i++) {
        kfree(nvdev->chan_table[i]);
        nvdev->chan_table[i] = NULL;
    }
    kfree(nvdev->chan_table);
    nvdev->chan_table = NULL;
    kfree(nvdev);
```

3. Using a separate function for channel cleanup:
```c
    cleanup_channels(nvdev);
    kfree(nvdev->chan_table);
    kfree(nvdev);
```

4. Checking for NULL before freeing:
```c
    if (nvdev->chan_table) {
        for (i = 0; i < nvdev->num_chn; i++) {
            if (nvdev->chan_table[i])
                kfree(nvdev->chan_table[i]);
        }
        kfree(nvdev->chan_table);
    }
    kfree(nvdev);
```

5. Using a macro for safe deallocation:
```c
    #define SAFE_FREE(ptr) do { if (ptr) { kfree(ptr); ptr = NULL; } } while (0)

    for (i = 0; i < nvdev->num_chn; i++)
        SAFE_FREE(nvdev->chan_table[i]);
    SAFE_FREE(nvdev->chan_table);
    SAFE_FREE(nvdev);
```