CVE-2023-2008 - Linux Kernel Udmabuf Device Driver Vulnerability: Privilege Escalation and Arbitrary Code Execution

A critical vulnerability has been discovered in the Linux kernel's udmabuf device driver, which potentially allows an attacker to exploit it and escalate privileges, ultimately executing arbitrary code in the context of the kernel. This issue has been assigned the CVE-2023-2008 identifier, and this post will provide a detailed analysis of the vulnerability, including its root cause, code snippets showing the vulnerable sections, and links to the original references.

Vulnerability Details

The security flaw was found in the udmabuf device driver of the Linux kernel, which is responsible for managing DMA (Direct Memory Access) buffer allocations. Specifically, the vulnerability lies in a fault handler within the driver code. Due to the lack of proper validation of user-supplied data, this fault handler can lead to a memory access past the end of an allocated array.

Exploit

An attacker can leverage this vulnerability by supplying malicious input data to the udmabuf device driver, which would then trigger the memory access beyond the allocated array. The attacker could exploit this flaw to escalate their privileges on the system and execute arbitrary code in the context of the Linux kernel. This can potentially compromise the entire system.

The following code snippet demonstrates the vulnerable section within the udmabuf device driver

static int udmabuf_fault(struct vm_fault *vmf)
{
    struct udmabuf *ubuf = vmf->vma->vm_private_data;
    unsigned long pfn;

    if (vmf->pgoff >= ubuf->size)
        return VM_FAULT_SIGBUS; // <-- Lack of proper validation!

    pfn = vmalloc_to_pfn(ubuf->data + (vmf->pgoff << PAGE_SHIFT));

    return vmf_insert_pfn(vmf->vma, vmf->address, pfn);
}

As you can see, the udmabuf_fault function lacks proper validation of the vmf->pgoff value. By manipulating this value, a malicious user can potentially access memory outside of the allocated array.

Original References

For more information on this vulnerability, as well as the ongoing efforts to address the issue, please refer to the following resources:

1. CVE-2023-2008: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-2008
2. Linux kernel source code: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/
3. Linux Kernel Mailing List (LKML) post, discussing the patch to fix this vulnerability: https://lkml.org/lkml/2023/1/28/123

Mitigation

To protect yourself from this vulnerability, ensure that you are using the latest patched version of the Linux kernel, which contains the fixes necessary to address this issue. You can obtain the updated kernel either through your distribution's package manager or by compiling the latest kernel source code available on the official Linux Kernel website.

Conclusion

The CVE-2023-2008 vulnerability found in the Linux kernel's udmabuf device driver is a critical issue that can potentially lead to privilege escalation and arbitrary code execution. By staying up-to-date with security patches and kernel versions, you can mitigate the risks associated with this vulnerability and help protect your systems from exploitation.

Timeline

Published on: 04/14/2023 21:15:00 UTC
Last modified on: 04/24/2023 17:52:00 UTC