struct file *perf_event_get(unsigned int fd)
{
	struct file *file;

	file = fget_raw(fd);
	if (!file)
		return ERR_PTR(-EBADF);

	if (file->f_op != &perf_fops) {
		fput(file);
		return ERR_PTR(-EBADF);
	}

	return file;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.