static struct file *path_openat(struct nameidata *nd,
			const struct open_flags *op, unsigned flags)
{
	const char *s;
	struct file *file;
	int opened = 0;
	int error;

	file = get_empty_filp();
	if (IS_ERR(file))
		return file;

	file->f_flags = op->open_flag;

	if (unlikely(file->f_flags & __O_TMPFILE)) {
		error = do_tmpfile(nd, flags, op, file, &opened);
		goto out2;
	}

	if (unlikely(file->f_flags & O_PATH)) {
		error = do_o_path(nd, flags, file);
		if (!error)
			opened |= FILE_OPENED;
		goto out2;
	}

	s = path_init(nd, flags);
	if (IS_ERR(s)) {
		put_filp(file);
		return ERR_CAST(s);
	}
	while (!(error = link_path_walk(s, nd)) &&
		(error = do_last(nd, file, op, &opened)) > 0) {
		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
		s = trailing_symlink(nd);
		if (IS_ERR(s)) {
			error = PTR_ERR(s);
			break;
		}
	}
	terminate_walk(nd);
out2:
	if (!(opened & FILE_OPENED)) {
		BUG_ON(!error);
		put_filp(file);
	}
	if (unlikely(error)) {
		if (error == -EOPENSTALE) {
			if (flags & LOOKUP_RCU)
				error = -ECHILD;
			else
				error = -ESTALE;
		}
		file = ERR_PTR(error);
	}
	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.