static void rdma_umap_close(struct vm_area_struct *vma)
{
	struct ib_uverbs_file *ufile = vma->vm_file->private_data;
	struct rdma_umap_priv *priv = vma->vm_private_data;

	if (!priv)
		return;

	/*
	 * The vma holds a reference on the struct file that created it, which
	 * in turn means that the ib_uverbs_file is guaranteed to exist at
	 * this point.
	 */
	mutex_lock(&ufile->umap_lock);
	list_del(&priv->list);
	mutex_unlock(&ufile->umap_lock);
	kfree(priv);
}

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.