Hello everyone,

Today, we will be discussing a significant vulnerability, assigned the identifier CVE-2022-2318, which affects the Linux kernel. The vulnerability resides in the net/rose/rose_timer.c file and involves use-after-free issues caused by the timer handler. This vulnerability could allow attackers to crash the kernel without requiring any administrative privileges, which poses a serious security threat to the Linux ecosystem.

In this post, we will examine the vulnerability in detail, discuss the specific code snippets involved, and explore the exploit method utilized by attackers. We will also provide references to the original research and discuss potential mitigation options.

Understanding the Vulnerability

The vulnerability is caused by use-after-free errors in the timer handler within the net/rose/rose_timer.c file of the Linux kernel. To understand this vulnerability, we must first discuss what "use-after-free" means. Use-after-free refers to a type of memory corruption that occurs when a program continues to use a memory pointer after its associated memory allocation has been freed. This can lead to crashes, data corruption, or even remote code execution.

In this case, the use-after-free issues in the rose_timer.c file may cause kernel memory corruption, leading to a kernel crash that attackers can exploit without requiring any privileges.

Code Snippets and Vulnerable Sections

The vulnerable section of the code is found within the Linux kernel's net/rose/rose_timer.c file. Here's a snippet of the code in question (simplified for clarity):

static void rose_idletimer_expiry(unsigned long param)
    struct rose_neigh *neigh = (struct rose_neigh *)param;
    if (atomic_read(&neigh->use) == )
        neigh->count = ;

    // ...

The vulnerability lies in the function rose_idletimer_expiry, which is called upon the expiry of the idle timer. The rose_neigh structure pointer, neigh, is passed as a parameter, and the function checks the current use count of the neigh object. If the use count is zero, the function sets the count of neigh to zero. However, there is no proper check before decrementing the use counter, which leads to a use-after-free situation.

Exploit Details

Attackers can exploit this use-after-free vulnerability to crash the kernel. While the specific steps to do so might vary depending on the Linux distribution and kernel version, in general, the attack would involve the following:

Trigger the rose_idletimer_expiry function at a time when the neigh object's use count is zero.

- Craft network packets to manipulate the neigh object after its memory has been freed, thereby achieving a use-after-free situation.

The vulnerability was first reported by security researchers on the Linux Kernel Mailing List (LKML)

- LKML: CVE-2022-2318 - Use-After-Free Vulnerability in net/rose/rose_timer.c

This post provides an in-depth explanation of the issue and the related proof-of-concept code to reproduce the vulnerability.

Mitigation Options

To mitigate this vulnerability, users are urged to update their systems with the latest Linux kernel patches. Vendors have released security updates addressing the vulnerability. It's crucial to regularly apply security patches to ensure your system is protected from such threats.

To summarize, CVE-2022-2318 is a critical vulnerability in the Linux kernel's net/rose/rose_timer.c file that could enable attackers to crash the kernel without any privileges. By understanding the vulnerability, monitoring exploit details, and applying the necessary patches, Linux administrators can keep their systems secure. As always, vigilance in maintaining software updates is crucial for ensuring the overall security of your systems.


Published on: 07/06/2022 19:15:00 UTC
Last modified on: 07/27/2022 11:15:00 UTC