CVE-2023-1829: Use-After-Free Vulnerability in Linux Kernel Traffic Control Index Filter (tcindex) Leads to Local Privilege Escalation

A serious use-after-free vulnerability has been discovered in the Linux Kernel's traffic control index filter (tcindex) subsystem (CVE-2023-1829). This vulnerability can potentially lead to a local privilege escalation attack, allowing malicious users to elevate their privileges to root. In this post, we will explore the details of the vulnerability, including the code snippet, relevant links to original references, and exploit details. We will also provide recommendations on how to mitigate this security risk.

Code Snippet

The vulnerability lies in the tcindex_delete function, which does not deactivate filters properly in case of a perfect hashes when deleting the underlying structure. This can lead to double freeing the structure. The code snippet of the vulnerable function is as follows:

static void tcindex_delete(struct tcf_proto *tp)
{
    struct tcindex_data *p = PRIV(tp);

    if (p->perfect) {
        int i;

        for (i = ; i < p->hash; i++) {
            struct tcindex_filter_result *r = p->perfect + i;

            tcf_unbind_filter(tp, &r->res);
        }
        kfree(p->perfect);
    }
    kfree(p);
}

Exploit Details

A local attacker, with minimal privileges, can exploit this vulnerability by creating a maliciously crafted tc command on a system running a vulnerable kernel. The attacker can then trigger the vulnerability by manipulating the traffic control filters, leading to double freeing the structure, and causing a use-after-free condition. This can potentially allow the attacker to execute arbitrary code with root privileges, gaining complete control of the affected system.

The following are links to the original references detailing the vulnerability

1. The Linux Kernel Mailing List (LKML) post discussing the vulnerability: https://lkml.org/lkml/2023/6/20/122
2. The GitHub Commit addressing the vulnerability: https://github.com/torvalds/linux/commit/8c710f75256bb3cf05ac7b1672c82b92c43f3d28
3. The National Vulnerability Database (NVD) entry for CVE-2023-1829: https://nvd.nist.gov/vuln/detail/CVE-2023-1829

Mitigation Recommendations

To mitigate this vulnerability, it is recommended to upgrade the Linux Kernel past commit 8c710f75256bb3cf05ac7b1672c82b92c43f3d28 which addresses the issue. You can update your kernel by following your distribution's guidelines or by compiling the latest version from the Linux Kernel source.

Conclusion

The CVE-2023-1829 use-after-free vulnerability in the Linux Kernel tcindex subsystem poses a serious security risk, allowing attackers to escalate their privileges to root. By understanding the details of the vulnerability, and taking the recommended mitigation steps of upgrading the kernel, you can ensure your systems are protected from potential exploitation. Stay safe and secure by regularly updating your systems and keeping informed about emerging security threats.

Timeline

Published on: 04/12/2023 12:15:00 UTC
Last modified on: 06/01/2023 14:15:00 UTC