A use-after-free vulnerability in the Linux kernel has been identified and resolved, specifically in the thermal debugfs module. This post will provide an overview of the vulnerability, its implications, and the fix that has been implemented to address this issue. We will also provide code snippets, original references, and exploit details for a better understanding of the problem and the solution.

Vulnerability Details

The vulnerability existed in the "thermal/debugfs" module of the Linux kernel, where the function thermal_debug_cdev_remove() could cause a use-after-free issue. This function was not protected by the cdev->lock, which meant that it could run parallel to thermal_debug_cdev_state_update() and potentially free the struct thermal_debugfs object used by the latter after it was checked against NULL.

If this were to happen, it could cause thermal_debug_cdev_state_update() to access memory that had already been freed, resulting in the kernel crashing.

Code Snippet

Here is the patch applied to fix the issue by locking the cdev->lock in thermal_debug_cdev_remove() around the value check and reset to NULL:

void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    struct thermal_debugfs *t;

    if (!cdev)
        return;

    mutex_lock(&cdev->lock);

    t = cdev->debugfs;
    cdev->debugfs = NULL;

    mutex_unlock(&cdev->lock);

    if (!t)
        return;

    debugfs_remove_recursive(t->cdev_state_dir);
    kfree(t);
}

References

The vulnerability and respective fix have been discussed in the Linux kernel mailing list. You can find the original discussion and patch submission at the following link:

- Linux Kernel Mailing List - Patch Submission

Exploit Details

Although there have been no known exploits of this vulnerability in the wild, it is essential to address the issue to prevent any potential exploitation. An attacker who can trigger this use-after-free vulnerability could cause kernel crashes or potentially escalate their privileges on the affected system.

Fix and Update

The fix for this issue has been applied, and it is recommended to update your Linux kernel to the latest stable version to ensure that your system is protected against this vulnerability. You can refer to your Linux distribution's documentation for instructions on how to update your Linux kernel.

Conclusion

By addressing the use-after-free vulnerability in the Linux kernel's thermal debugfs module, we can prevent potential kernel crashes or system compromises due to this issue. Ensuring that your system is up to date with the latest security patches is crucial in maintaining the overall security of your Linux environment.

Timeline

Published on: 05/30/2024 16:15:16 UTC
Last modified on: 06/10/2024 19:20:40 UTC