A recent vulnerability has been discovered and resolved in the Linux kernel's iwlwifi module, which manages the wireless network interfaces for Intel-based hardware. This vulnerability, known as CVE-2024-53055, stemmed from an issue related to 6 GHz WiFi scanning. In this post, we will explore the specifics of the vulnerability, provide a code snippet illustrating the fix, and discuss the potential implications of this exploit.

Vulnerability Details

The CVE-2024-53055 vulnerability occurs during the construction of a 6 GHz WiFi scan when there are more than 255 colocated access points (APs) found during the 2.4/5 GHz scanning process. The issue lies in the type of loop variable used, which is an 8-bit unsigned integer (u8). When the number of APs exceeds 255, the loop variable would never reach the required value and result in an infinite loop. The original reference that reported this vulnerability can be found here.

Code Snippet Fix

To resolve this vulnerability, the loop variable in question has been changed to a 32-bit unsigned integer (u32). In addition, the variable's scope has been minimized by moving it into the loops. The following code snippet demonstrates the fix:

u32 num_remaining_entries;

for (entries = desc->entries, num_entries = desc->n_entries;
     num_remaining_entries = desc->num_remaining_entries;
     entries = RNR_OFFSET(entries, num_remaining_entries))
     num_remaining_entries = get_remaining_entries(entries, num_entries);

With this change, the loop variable can now accommodate a much larger range of values, making it suitable to handle situations where there are more than 255 colocated APs. Each AP has a limit on the number of RNR entries due to frame size constraints, and with an upper limit of 100 scan results, a frame size upper bound of 4096 (in reality, around 230), and a TBTT entry size of at least 11, the maximum number of APs is well within the bounds of a u32.

Exploit Implications

This vulnerability's main impact is in situations where a large number of colocated APs are present, which could lead to a potentially significant delay in the 6 GHz WiFi scanning process. It is important to note that the vulnerability does not directly compromise the security or integrity of the system or network. However, in environments with a high density of APs, it could negatively impact the system's performance and reliability.

Conclusion

The CVE-2024-53055 vulnerability highlights the importance of thoroughly testing complex systems, such as the Linux kernel, to ensure smooth and secure operation. Properly addressing and patching such vulnerabilities is crucial in maintaining and improving the overall security and performance of these systems. With the fix discussed in this post, this particular vulnerability has been effectively addressed, providing a safer and more efficient 6 GHz WiFi scanning process for Linux systems utilizing the iwlwifi module.

Timeline

Published on: 11/19/2024 18:15:25 UTC
Last modified on: 11/22/2024 17:18:33 UTC