The provided code snippet does not seem to have a CWE-787 (Out-of-bounds Write) vulnerability at line 4. The `kmalloc` function is used to allocate memory dynamically, and it does not perform any write operation beyond the allocated memory.

Without additional context or information about the `hbq_dmabuf` structure, it is difficult to identify any potential out-of-bounds write vulnerability in this code snippet.

If there is a specific concern or additional information about the vulnerability, please provide more details or context.