The root cause of the CWE-190  vulnerability in the given code slice is:

The code performs a modulo operation (%) using the value of sp->bytes_per_line without first checking if it is zero. If sp->bytes_per_line is zero, this will result in a divide-by-zero error, which can lead to a program crash or unexpected behavior.

To prevent this vulnerability, the code should include a check to ensure that sp->bytes_per_line is not zero before performing the modulo operation. For example:

```c
if (sp->bytes_per_line != 0 && cc % sp->bytes_per_line != 0)
```

This check would prevent the divide-by-zero error by only executing the modulo operation when sp->bytes_per_line is non-zero.