In the constantly evolving world of operating systems, vulnerabilities are bound to emerge. Security researchers and programmers work continuously to identify and fix the flaws that may compromise our devices’ safety and functionality. One such recent vulnerability, discovered in the Linux kernel, pertains to the kernel's WiFi functionality - specifically, the ath12k driver. The vulnerability has been assigned CVE-2023-52769, and the issue has been resolved in the latest kernel version. In this post, we'll dive into the details of this vulnerability, its implications, and how the fix was implemented.

Background and Original References

The ath12k driver is responsible for handling WiFi communication. This particular vulnerability involved the event handling code for the Hydration Technical Vantage Point (HTT) MLO-offset event (Multiple Listening/Open-Ended Detection). The communication with the pdev was not marked as a read-side critical section. The code snippet where the issue existed is as follows:

static void ath12k_htt_rx_hl_ptr_incr(struct ath12k_htt* htt, u32 ev_id)
{
  struct ath12k * ar = ath12k_mac_get_ar_by_pdev_id(htt->ar, ev_id);
  ...
}

Original references for this vulnerability and its resolution include

- Commit Message - ath12k: fix HTT MLO-Offset Event Locking
- Linux Kernel Mailing List

Exploit Details

The vulnerability posed risks of use-after-free issues. In simple terms, this means that memory could have been accessed even after it was freed, potentially making the system susceptible to crashes or security breaches.

Specifically, the code sequence in question wasn't protected by the RCU (Read-Copy-Update) mechanism. If the operating system happened to deallocate the memory object holding the event handler while it was being processed, the event handler would have been able to access the freed memory, leading to serious adverse consequences.

The Fix

To address the vulnerability, the Linux kernel developers marked the code in question as an RCU read-side critical section. This helps ensure that a use-after-free issue won't occur by preventing the system from deallocating the ev_id object until the ath12k_mac_get_ar_by_pdev_id() function has completed processing it.

The updated code snippet with the fix applied is as follows

static void ath12k_htt_rx_hl_ptr_incr(struct ath12k_htt* htt, u32 ev_id)
{
  rcu_read_lock();
  struct ath12k * ar = ath12k_mac_get_ar_by_pdev_id(htt->ar, ev_id);
  ...
  rcu_read_unlock();
}

By using the rcu_read_lock() and rcu_read_unlock() functions, the kernel ensures proper synchronization and protection of the active pdevs. The fix has been implemented in the latest kernel release, so end-users should update their systems to the latest kernel versions to avoid any potential issues related to this vulnerability.

Conclusion

CVE-2023-52769 was a significant vulnerability that affected the Linux kernel's ath12k WiFi driver. Thorough assessment and prompt action by the Linux kernel community have led to the development and implementation of a successful fix. While this issue has been addressed, it serves as a reminder to maintain vigilance and stay up-to-date with the latest kernel versions and patches. Doing so ensures that our devices remain protected against known vulnerabilities and continue to operate safely and efficiently.

Timeline

Published on: 05/21/2024 16:15:16 UTC
Last modified on: 05/29/2024 05:17:02 UTC