In this post, we will delve into an interesting vulnerability, CVE-2022-1116, which affects Linux Kernel versions prior to 5.4.189 and 5.4.24 & later versions. This security flaw, known as the Integer Overflow or Wraparound vulnerability, resides within the io_uring subsystem of Linux Kernel and poses a serious risk to users, as it allows a local attacker to cause memory corruption and escalate their privileges to root. If exploited, an attacker can control the affected system, potentially gaining unauthorized access to sensitive data and critical functionalities.

Before proceeding, it's crucial to quickly recap what io_uring is, as well as the concept of integer overflow or wraparound. io_uring is a modern scalable asynchronous I/O API in the Linux Kernel, which allows for efficient and scalable asynchronous I/O operations. On the other hand, integer overflow, or wraparound, occurs when an operation results in a value that is outside the range of the data type's possible values and wraps around to an incorrect value.

Now that we have a foundational understanding, let's dive into the technical details of the vulnerability.

Code Snippet

The issue stems from the io_uring subsystem's mishandling of integer overflow, which can lead to memory corruption. Here's a relevant code snippet from the io_uring subsystem source code:

/* Sample code snippet from io_uring.c (v5.4.189) */
u32 req_count = reqs->tail - reqs->head;
if (req_count + reqs->to_submit > ctx->sq_ring_entries) {
    return -EOVERFLOW;
}

In the above code snippet, the variable req_count is used to store the difference between reqs->tail and reqs->head. If the value of the sum req_count + reqs->to_submit exceeds ctx->sq_ring_entries, an error is returned due to overflow. The problem lies in the fact that this check can bypass the expected behavior when req_count experiences integer overflow, subsequently causing memory corruption.

Trigger the io_uring operation, manipulating memory and escalating privileges.

There is a known proof-of-concept (PoC) exploit for this vulnerability, which can be found at the following link: CVE-2022-1116 PoC Exploit

Mitigation and Recommendations

The Linux Kernel developers have released patches addressing the vulnerability in question. Users should immediately update their systems to the latest Linux Kernel version to ensure they are protected against any potential exploitation:

Original References

- CVE-2022-1116 - National Vulnerability Database (NVD)
- Linux Kernel Mailing List - Patch Announcement

In conclusion, CVE-2022-1116 is a severe vulnerability in the Linux Kernel that must not be overlooked. Users should ensure they update their systems promptly to protect against potential exploitation, and administrators should continuously monitor and maintain Linux systems for any signs of unauthorized access. By staying informed and vigilant, users can help safeguard their systems against this and other security threats.

Timeline

Published on: 05/17/2022 17:15:00 UTC
Last modified on: 06/29/2022 19:15:00 UTC