static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct file *lower_file = ecryptfs_file_to_lower(file);
	/*
	 * Don't allow mmap on top of file systems that don't support it
	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
	 * allows recursive mounting, this will need to be extended.
	 */
	if (!lower_file->f_op->mmap)
		return -ENODEV;
	return generic_file_mmap(file, vma);
}
The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.