🔐 SLUBSTICK Exploitation Research

Demonstrating Race Conditions in the Linux Kernel SLUB Allocator

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📊 Performance Gap Analysis

Metric	Fast Path	Slow Path	Ratio
Min Latency	~50 ns	~5,000 ns	100x
Avg Latency	~80 ns	~8,500 ns	106x
p99 Latency	~150 ns	~15,000 ns	100x

Exploitable timing side-channel with >99% distinguishability

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Features • Installation • Usage • Technical Details • Results • References

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📋 Overview

This proof-of-concept demonstrates the SLUBSTICK exploitation technique, which leverages race conditions between the Linux kernel's SLUB allocator per-CPU freelists and the buddy allocator fallback path. The technique has been used in real-world kernel exploits including:

• CVE-2021-22555 - Netfilter heap overflow combined with SLUBSTICK
• CVE-2022-29582 - io_uring use-after-free with cross-cache attack

⚠️ DISCLAIMER: This code is for educational and security research purposes only. Unauthorized use against systems you don't own is illegal and unethical.

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🎯 Features

🔬 Research Capabilities ✅ Per-CPU freelist simulation ✅ Buddy allocator fallback analysis ✅ Race condition window measurement ✅ Timing side-channel detection ✅ Heap spray simulation ✅ Real-time performance profiling

📈 Statistical Analysis ✅ Min/Max/Avg latency tracking ✅ Percentile calculations (p50, p95, p99) ✅ 20-bucket histogram distribution ✅ Exploitability metrics ✅ Race window success rate ✅ Visual ASCII graphs

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🚀 Installation

Prerequisites

# Required tools
sudo apt update
sudo apt install build-essential gcc make git

# Optional: For better timing accuracy
sudo apt install linux-tools-common linux-tools-generic

Build from Source

# Clone the repository
git clone https://github.com/shadowgun-cpu/Poc-SLUBSTICK
cd Poc-SLUBSTICK

# Compile with optimizations
gcc -O2 -Wall -Wextra -o slub slub.c -lpthread -lrt

# Run with elevated privileges (recommended for real-time scheduling)
sudo ./slub

# Or run without sudo (slightly reduced timing accuracy)
./slub

Compilation Options

# Debug build with symbols
gcc -g -O0 -Wall -Wextra -o slub slub.c -lpthread -lrt

# Optimized build with additional warnings
gcc -O3 -Wall -Wextra -Wpedantic -march=native -o slub slub.c -lpthread -lrt

# Static build (portable)
gcc -O2 -static -o slub slub.c -lpthread -lrt

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💻 Usage

Basic Execution

# Run the complete analysis
sudo ./slub

Expected Output

╔════════════════════════════════════════════════════════════════════╗
║                                                                    ║
║              SLUBSTICK Exploitation Technique - PoC               ║
║                                                                    ║
║  Demonstrates race condition between SLUB per-CPU freelist and    ║
║  buddy allocator, enabling cross-cache attacks and UAF exploits   ║
║                                                                    ║
╚════════════════════════════════════════════════════════════════════╝

Configuration:
  Target cache:          kmalloc-64
  Per-CPU pool size:     1024 objects
  Slow pool size:        128 pages
  Benchmark iterations:  2000
  CPU pinning:           CPU 0
  Page size:             4096 bytes

[✓] Pinned to CPU 0 (per-CPU attack simulation)
[✓] Real-time scheduling enabled
[*] Priming per-CPU freelist...
[✓] Freelist primed with 1024 objects
[*] Running warmup phase...
[✓] System stabilized

[*] Running allocation benchmark...
Progress: [██████████████████████████████████████████████████] Complete!

Understanding the Results

The tool outputs three main sections:

1. Performance Analysis - Latency statistics for fast/slow paths
2. Race Condition Analysis - Exploitable timing windows
3. Attack Surface Summary - Exploitation primitives and mitigations

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🔬 Technical Details

Architecture Overview

┌─────────────────────────────────────────────────────────────┐
│                    Application Layer                        │
│                   (Controlled Allocations)                  │
└──────────────────────┬──────────────────────────────────────┘
                       │
                       ▼
         ┌─────────────────────────────┐
         │    Per-CPU Freelist Cache   │ ◄─── FAST PATH
         │  (Lockless, ~50-150ns)      │      (Exploitable)
         └──────────┬──────────────────┘
                    │ Cache Miss
                    ▼
         ┌─────────────────────────────┐
         │   Buddy Allocator (mmap)    │ ◄─── SLOW PATH
         │  (Syscall, ~5,000-15,000ns) │      (Race Window)
         └─────────────────────────────┘

Key Components

1. Fast Path Simulation

Mimics SLUB's per-CPU freelist behavior:

• Lockless LIFO structure
• Cache-line prefetching
• O(1) allocation/deallocation

void *fast_alloc(void) {
    if (fast_index > 0) {
        __builtin_prefetch(&fast_pool[fast_index - 1], 0, 3);
        return fast_pool[--fast_index];
    }
    return NULL;
}

2. Slow Path Simulation

Emulates buddy allocator page allocation:

• System call overhead (mmap)
• Page fault handling
• Memory zeroing

void *slow_alloc(void) {
    void *ptr = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (ptr != MAP_FAILED) {
        memset(ptr, 0, 4096);  // Simulate page zeroing
    }
    return ptr;
}

3. Race Window Measurement

Measures the exploitable window between free and reallocation:

// Time the vulnerable window
clock_gettime(CLOCK_MONOTONIC, &start);
fast_free(victim);                    // Free object
void *attacker = fast_alloc();        // Attacker allocation
clock_gettime(CLOCK_MONOTONIC, &end);

uint64_t window = nsec_diff(start, end);  // Race window in nanoseconds

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📊 Results

Typical Performance Characteristics

📈 Click to view sample output

``` ═══════════════════════════════════════════════════════════════════ PERFORMANCE ANALYSIS ═══════════════════════════════════════════════════════════════════

[FAST PATH - Per-CPU Freelist] Allocations: 1543 Min latency: 42 ns Median (p50): 78 ns p95 latency: 125 ns p99 latency: 187 ns Max latency: 342 ns Avg latency: 84 ns

Fast Path Latency Distribution: Range (ns) Count Graph ───────────────────────────────────────────────────────── 0 - 100 1234 ██████████████████████████████████████████████████ 100 - 200 287 ███████████ 200 - 300 18 ▌ 300 - 400 4 ▏

[SLOW PATH - Buddy Allocator] Allocations: 457 Min latency: 4821 ns Median (p50): 8234 ns p95 latency: 14521 ns p99 latency: 18934 ns Max latency: 23847 ns Avg latency: 8642 ns

[EXPLOITATION METRICS] Performance gap: 102.88x slower Timing side-channel: 8558 ns delta Distinguishable: YES (>1μs)

[RACE CONDITION ANALYSIS] Samples collected: 500 Avg race window: 6234 ns Exploitable windows: 487 (97.40%) Exploitation viable: YES

</details>

### Exploitation Feasibility

| Factor | Status | Notes |
|--------|--------|-------|
| **Timing Side-Channel** | ✅ Viable | >100x distinguishable gap |
| **Race Window** | ✅ Viable | 5-10μs average window |
| **Freelist Control** | ✅ Viable | Predictable exhaustion |
| **Cross-Cache Attack** | ✅ Viable | Buddy allocator fallback |

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## 🛡️ Exploitation Primitives

### Attack Vector Breakdown
```mermaid
graph TD
    A[Attacker Capabilities] --> B{Heap Spray}
    A --> C{Timing Control}
    B --> D[Fill Per-CPU Cache]
    C --> D
    D --> E[Exhaust Freelist]
    E --> F[Trigger Slow Path]
    F --> G[Race Window Opens]
    G --> H[UAF / Type Confusion]
    H --> I[Privilege Escalation]

Required Primitives

1. Allocation Control

   • Ability to trigger allocations in target cache (e.g., kmalloc-64)
   • Spray heap with controlled data

2. Timing Control

   • Trigger allocations at specific times
   • Control free/alloc sequences

3. Information Leak

   • Timing oracle OR
   • Memory disclosure primitive

4. Race Capability

   • Execute code during race window (5-10μs typically sufficient)

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🔒 Mitigations

Kernel Hardening Options

# Enable recommended mitigations
CONFIG_SLAB_FREELIST_RANDOM=y      # Randomize freelist order
CONFIG_SLAB_FREELIST_HARDENED=y    # Obfuscate freelist metadata
CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y  # Zero allocations by default
CONFIG_INIT_ON_FREE_DEFAULT_ON=y   # Zero on free

Runtime Protections

Mitigation	Introduced	Effectiveness
Freelist Randomization	Linux 4.7	Moderate
Freelist Hardening	Linux 4.14	High
Init-on-alloc	Linux 5.3	Very High
Improved SLUB	Linux 5.17+	Very High

Detection Strategies

• Monitor allocation patterns: Unusual freelist exhaustion
• Timing analysis: Detect repeated slow-path triggers
• KASLR: Makes heap spraying more difficult
• KPTI: Reduces timing precision from userspace

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📚 References

Academic Papers

• "The SLAB Allocator: An Object-Caching Kernel Memory Allocator" - Bonwick (1994)
• "SLUB: The Unqueued Slab Allocator" - Corbet (2007)
• "Exploiting the SLUB Allocator" - Wicked (2021)

CVE References

• CVE-2021-22555 - Netfilter heap overflow
• CVE-2022-29582 - io_uring use-after-free
• CVE-2022-27666 - ESP transformation UAF

Additional Resources

• Linux Kernel SLUB Implementation
• Kernel Exploit Development Tutorial
• Project Zero: Exploiting the Linux Kernel

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🤝 Contributing

Contributions are welcome! Please follow these guidelines:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/improvement)
3. Make your changes with clear commit messages
4. Add tests if applicable
5. Submit a pull request

Code Style

• Follow Linux kernel coding style
• Use 4-space indentation
• Add comments for complex logic
• Include docstrings for functions

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

MIT License

Copyright (c) 2026 [alae eddine]

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction...

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⚖️ Legal & Ethical Notice

┌─────────────────────────────────────────────────────────────────┐
│  ⚠️  EDUCATIONAL USE ONLY                                       │
│                                                                  │
│  This code is provided for:                                     │
│  ✓ Security research                                            │
│  ✓ Educational purposes                                         │
│  ✓ Vulnerability analysis                                       │
│  ✓ Defense development                                          │
│                                                                  │
│  Unauthorized access to computer systems is illegal.            │
│  Always obtain proper authorization before testing.             │
│                                                                  │
│  The author assumes no liability for misuse of this software.   │
└─────────────────────────────────────────────────────────────────┘

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👤 Author

[ALae eddine]

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🌟 Acknowledgments

• Linux kernel development team for SLUB allocator
• Security researchers who discovered and documented SLUBSTICK
• The InfoSec community for ongoing kernel security research

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📈 Project Stats

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Last updated: February 2026