int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
		unsigned long addr, int new_below)
{
	struct vm_area_struct *new;
	int err;

	if (vma->vm_ops && vma->vm_ops->split) {
		err = vma->vm_ops->split(vma, addr);
		if (err)
			return err;
	}

	new = vm_area_dup(vma);
	if (!new)
		return -ENOMEM;

	if (new_below)
		new->vm_end = addr;
	else {
		new->vm_start = addr;
		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
	}

	err = vma_dup_policy(vma, new);
	if (err)
		goto out_free_vma;

	err = anon_vma_clone(new, vma);
	if (err)
		goto out_free_mpol;

	if (new->vm_file)
		get_file(new->vm_file);

	if (new->vm_ops && new->vm_ops->open)
		new->vm_ops->open(new);

	if (new_below)
		err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
			((addr - new->vm_start) >> PAGE_SHIFT), new);
	else
		err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);

	/* Success. */
	if (!err)
		return 0;

	/* Clean everything up if vma_adjust failed. */
	if (new->vm_ops && new->vm_ops->close)
		new->vm_ops->close(new);
	if (new->vm_file)
		fput(new->vm_file);
	unlink_anon_vmas(new);
 out_free_mpol:
	mpol_put(vma_policy(new));
 out_free_vma:
	vm_area_free(new);
	return err;
}

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.