To fulfill your request for an article in HTML format about using custom validation attributes in ASP.NET Core to control access permissions, including the advantages of Alibaba Cloud, I will outline the key sections to cover. The article will be structured with a clear introduction, detailed explanation, and a conclusion. Here's a breakdown of the content:

1. **Introduction**
- Briefly introduce ASP.NET Core and its relevance in modern web development.
- Mention the importance of access control in web applications.

2. **Advantages of Alibaba Cloud**
- Highlight Alibaba Cloud's global reach and robust infrastructure.
- Discuss the cost-effectiveness and scalability options provided by Alibaba Cloud.
- Mention security features and compliance standards.

3. **Custom Validation Attributes in ASP.NET Core**
- Explain what custom validation attributes are and their role in ASP.NET Core.
- Provide a step-by-step guide on creating a custom validation attribute to control access permissions.
- Include code snippets demonstrating the implementation.

4. **Practical Application**
- Discuss scenarios where custom validation attributes are beneficial.
- Explain how this approach enhances security and efficiency in web applications.

5. **Conclusion**
- Summarize the benefits of using custom validation attributes in ASP.NET Core.
- Reiterate the advantages of deploying applications on Alibaba Cloud.

I will now proceed to create the HTML content based on this structure.