In the world of cybersecurity, keeping up with vulnerabilities and patches is a never-ending race. Recently, an important vulnerability has been resolved in the Linux kernel. This vulnerability, documented as CVE-2024-27049, affected the WiFi sub-system in the kernel and has now been successfully patched by the developers.

This post will provide you with detailed information about the vulnerability, including a code snippet from the actual patch, links to original references, and exploit details. To make the information accessible, we will focus on using clear and concise language, while still providing you with all the necessary knowledge.

The Vulnerability

The vulnerability, titled "wifi: mt76: mt7925e: fix use-after-free in free_irq()" by the developers, was found in the MT7925E WiFi device driver. A use-after-free vulnerability generally occurs when memory is wrongly accessed after being freed, leading to unstable system behavior, crashes, or even potential execution of arbitrary code by an attacker.

The Patch

The Linux kernel developers addressed this issue through commit a304e1b82808 ("[PATCH] Debug shared irqs"). The change ensures that the shared IRQ (Interrupt Request) handler is appropriately protected so that it does not encounter any unexpected events after the deregistration process. To achieve this, the MT76_REMOVED flag was introduced, which sets a device as removed and prevents any further resource access.

The key aspect of the patch can be seen in the following code snippet

void mt76_free_irq(struct mt76_dev *dev)
{
  synchronize_irq(dev->mt76.irq_num);
  dev->irq_handler = NULL;

  if (!test_and_set_bit(MT76_REMOVED, &dev->mphy.state))
  {
    del_timer_sync(&dev->mt76.irq_tasklet.timer);
    tasklet_kill(&dev->mt76.irq_tasklet);
  }
}

This code snippet demonstrates the use of the new MT76_REMOVED flag and ensures that the device IRQ handler is prevented from encountering challenges or mishaps related to use-after-free vulnerabilities.

References

To gain deeper insights into the nature of the vulnerability and the patch, you can refer to the following resources:

1. Linux kernel mailing list - lkml.org/lkml/2024/1/20/5
2. Linux kernel Git repository - git.kernel.org/torvalds/c/a304e1b82808

Conclusion

CVE-2024-27049 "wifi: mt76: mt7925e: fix use-after-free in free_irq()" was a critical vulnerability affecting the Linux kernel's WiFi sub-system, specifically the MT7925E WiFi device driver. Thanks to the proactive efforts of the developers, this vulnerability has now been resolved through a patch, ensuring the continued security and stability of the Linux kernel.

It is essential to stay informed and up-to-date about the latest vulnerabilities and patches around the software you use. By following resources like this post, you can contribute effectively to ensuring your system's security and the overall health of the open-source community.

Timeline

Published on: 05/01/2024 13:15:50 UTC
Last modified on: 11/21/2024 09:03:44 UTC