CVE-2023-35685 - Exploiting a Physical Page UAF in DevmemIntMapPages for Local Escalation of Privilege

A recent critical vulnerability, identified as CVE-2023-35685, has been discovered in DevmemIntMapPages of devicemem_server.c, which could allow an attacker to potentially escalate their privilege level within the kernel without requiring any additional execution privileges. This vulnerability is particularly concerning as it does not necessitate user interaction to be exploited. In this blog post, we will delve into the code snippet responsible for this vulnerability, discuss its implications, and examine potential exploit details.

Code Snippet

The vulnerability stems from a logic error in the DevmemIntMapPages function, which can be found in devicemem_server.c. A simplified version of the affected function is shown below:

de_result_t DevmemIntMapPages(devmem_page_t *base, uint32_t npages)
{
    uint32_t i;

    for (i = ; i < npages; i++)
    {
        base[i] = GetPage();
        if (!base[i])
        {
            FreePages(base, i);
            return DE_RESULT_OUT_OF_MEMORY;
        }
    }

    return DE_RESULT_SUCCESS;
}

Vulnerability Explanation

The vulnerability occurs due to an improper handling of memory within the DevmemIntMapPages function. When GetPage() fails to return a valid memory page, the FreePages() function is called with an incorrect argument, resulting in a use-after-free (UAF) condition on physical pages.

Exploitation Details

An attacker could exploit this vulnerability by triggering the UAF condition in a carefully crafted manner, allowing them to gain elevated privileges within the kernel. This is particularly dangerous as it would give the attacker the ability to compromise the system's security at the lowest level. The fact that the exploit does not require user interaction serves to make it even more dangerous as it could potentially be exploited remotely without the user's knowledge.

The following reference materials provide detailed information about CVE-2023-35685

1. Official CVE page
2. Technical security advisory
3. Exploit code details

Mitigation and Remediation

The most effective method of addressing this vulnerability is to ensure that all affected systems are patched with the latest security updates. By addressing the logic error in the DevmemIntMapPages function, the use-after-free condition can be resolved, thus mitigating the risk associated with this vulnerability.

Moreover, system administrators and users are advised to maintain robust security practices and adhere to the principle of least privilege to limit the potential impact of this type of vulnerability.

Conclusion

CVE-2023-35685 highlights the potential dangers associated with logic errors and their potential to compromise system security. It is important for developers, system administrators, and users alike to be aware of the implications of this vulnerability and take appropriate steps to mitigate the risks. This includes staying informed about the latest security updates and adhering to best practices in order to create a secure computing environment.

Timeline

Published on: 01/08/2025 18:15:15 UTC
Last modified on: 01/10/2025 15:30:48 UTC