📑 Table of Contents

• Overview
• Technical Summary
• Root Cause
• Attack Flow
• Impact
• Affected Versions
• Detection
• Mitigation
• Timeline
• References
• Disclaimer

📌 Overview

🔍 Technical Summary

The vulnerability resides inside the Linux kernel's Real-Time Mutex (rtmutex) implementation.

During proxy-lock rollback, the function responsible for removing a waiter from the Priority Inheritance (PI) tree incorrectly operates on the current task instead of the actual waiting task.

This logic error leaves stale references inside kernel synchronization structures.

Eventually, the kernel may dereference memory that has already been freed, producing a classic Use-After-Free condition.

🧠 Root Cause

Affected source file:

kernel/locking/rtmutex.c

Affected routine:

remove_waiter()

Issue:

Incorrect task reference
        │
        ▼
Wrong waiter removed
        │
        ▼
Priority Inheritance tree becomes inconsistent
        │
        ▼
Dangling pi_blocked_on pointer
        │
        ▼
Freed object referenced later
        │
        ▼
Use-After-Free

⚙️ Attack Flow

User Process
      │
      ▼
futex_requeue()
      │
      ▼
rt_mutex_start_proxy_lock()
      │
      ▼
remove_waiter()
      │
      ▼
Incorrect cleanup
      │
      ▼
Dangling pointer
      │
      ▼
Kernel accesses freed memory
      │
      ▼
Memory Corruption

💥 Impact

Successful exploitation may result in:

• 🔴 Local Privilege Escalation
• 🔴 Kernel Memory Corruption
• 🔴 Kernel Panic
• 🔴 Denial of Service
• 🔴 System Instability
• 🔴 Potential Security Boundary Bypass

🖥️ Affected Versions

🔬 Exploitation Requirements

Typical prerequisites include:

• Local code execution
• Access to futex system calls
• Triggering proxy locking paths
• Vulnerable Linux kernel
• Precise synchronization timing

Note: Public advisories describe the vulnerability and its impact. Practical exploit reliability depends on kernel configuration, scheduling, and mitigation features.

🛡️ Detection

Administrators should monitor for:

• Kernel Oops
• Kernel Panic
• KASAN reports
• Unexpected rtmutex warnings
• futex-related crashes

Useful commands:

uname -r
journalctl -k
dmesg | grep -Ei "rtmutex|BUG|Oops|KASAN|futex"

🔒 Mitigation

• Upgrade to a patched Linux kernel.
• Apply vendor security updates promptly.
• Reboot after installing updates.
• Restrict local access on shared systems until patched.
• Monitor Linux kernel security advisories for backported fixes.

📅 Timeline

📚 References

• National Vulnerability Database (NVD)
• Linux Kernel Stable Patch
• Linux Kernel Git Repository
• Vendor Security Advisories

⚠️ Disclaimer

This repository is intended solely for educational, defensive, and security research purposes.

It does not include exploit code, weaponized payloads, or offensive tooling.

Always follow responsible disclosure practices and test only in environments that you own or are explicitly authorized to assess.