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1. Icarus: Trustworthy Just-In-Time Compilers with Symbolic Meta-Execution

   Smith, Naomi ; Sharma, Abhishek ; Renner, John ; Thien, David ; Brown, Fraser ; Shacham, Hovav ; Jhala, Ranjit ; Stefan, Deian ( November 2024 , Association for Computing Machinery)

   Arpaci-Dusseau, Andrea ; Keeton, Kimberly (Ed.)

   Just-in-time (JIT) compilers make JavaScript run efficiently by replacing slow JavaScript interpreter code with fast machine code. However, this efficiency comes at a cost: bugs in JIT compilers can completely subvert all language-based (memory) safety guarantees, and thereby introduce catastrophic exploitable vulnerabilities. We present Icarus: a new framework for implementing JIT compilers that are automatically, formally verified to be safe, and which can then be converted to C++ that can be linked into browser runtimes. Crucially, we show how to build a JIT with Icarus such that verifying the JIT implementation statically ensures the security of all possible programs that the JIT could ever generate at run-time, via a novel technique called symbolic meta-execution that encodes the behaviors of all possible JIT-generated programs as a single Boogie meta-program which can be efficiently verified by SMT solvers. We evaluate Icarus by using it to re-implement components of Firefox's JavaScript JIT. We show that Icarus can scale up to expressing complex JITs, quickly detects real-world JIT bugs and verifies fixed versions, and yields C++ code that is as fast as hand-written code. 

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2. Automatically Localizing Dynamic Code Generation Bugs in JIT Compiler Back-End

   https://doi.org/10.1145/3578360.3580260  

   Lim, HeuiChan ; Debray, Saumya ( February 2023 , ACM)

   Just-in-Time (JIT) compilers are ubiquitous in modern computing systems and are used in a wide variety of software. Dynamic code generation bugs, where the JIT compiler silently emits incorrect code, can result in exploitable vulnerabilities. They, therefore, pose serious security concerns and make quick mitigation essential. However, due to the size and complexity of JIT compilers, quickly locating and fixing bugs is often challenging. In addition, the unique characteristics of JIT compilers make existing bug localization approaches inapplicable. Therefore, this paper proposes a new approach to automatic bug localization, explicitly targeting the JIT compiler back-end. The approach is based on explicitly modeling architecture-independent back-end representation and architecture-specific code-generation. Experiments using a prototype implementation on a widely used JIT compiler (Turbofan) indicate that it can successfully localize dynamic code generation bugs in the back-end with high accuracy. 

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3. Automated bug localization in JIT compilers

   https://doi.org/10.1145/3453933.3454021  

   Lim, HeuiChan ; Debray, Saumya ( April 2021 , Proceedings of the 17th ACM SIGPLAN/SIGOPS International Conference on Virtual Execution Environments (VEE ’21))

   null (Ed.)

   Many widely-deployed modern programming systems use just-in-time (JIT) compilers to improve performance. The size and complexity of JIT-based systems, combined with the dynamic nature of JIT-compiler optimizations, make it challenging to locate and fix JIT compiler bugs quickly. At the same time, JIT compiler bugs can result in exploitable security vulnerabilities, making rapid bug localization important. Existing work on automated bug localization focuses on static code, i.e., code that is not generated at runtime, and so cannot handle bugs in JIT compilers that generate incorrect code during optimization. This paper describes an approach to automated bug localization in JIT compilers, down to the level of distinct optimization phases, starting with a single initial Proof-of-Concept (PoC) input that demonstrates the bug. Experiments using a prototype implementation of our ideas on Google’s V8 JavaScript interpreter and TurboFan JIT compiler demonstrates that it can successfully identify buggy optimization phases. 

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4. Modeling code manipulation in JIT compilers

   https://doi.org/10.1145/3520313.3534656  

   Lim, HeuiChan ; Kang, Xiyu ; Debray, Saumya ( June 2022 , Proceedings of the 11th ACM SIGPLAN International Workshop on the State Of the Art in Program Analysis)

   Gonnord, Laure ; Titolo, Laura (Ed.)

   Just-in-Time (JIT) compilers are widely used to improve the performance of interpreter-based language implementations by creating optimized code at runtime. However, bugs in the JIT compiler’s code manipulation and optimization can result in the generation of incorrect code. Such bugs can be difficult to diagnose and fix, and can result in exploitable vulnerabilities. Unfortunately, existing approaches to automatic bug localization do not carry over well to such bugs. This paper discusses a different approach to analyzing JIT compiler optimization behaviors, based on using dynamic analysis to construct abstract models of the JIT compiler’s optimizer and back end. By comparing the models obtained for buggy and non-buggy executions of the JIT compiler, we can pinpoint the components of the JIT compiler’s internal representation that have been affected by the bug; this can then be mapped back to identify the buggy code. Our ex- periments with two real bugs for Google V8 JIT compiler, TurboFan, show the utility and practicality of our approach. 

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5. A Framework for Automatic Exploit Generation for JIT Compilers

   https://doi.org/10.1145/3465413.3488573  

   Kang, Xiyu ; Debray, Saumya ( November 2021 , Checkmate '21: Proceedings of the 2021 Research on offensive and defensive techniques in the Context of Man At The End (MATE) Attacks)

   Kwon, Yonghwi ; Banescu, Sebastian (Ed.)

   This paper proposes a framework for automatic exploit generation in JIT compilers, focusing in particular on heap corruption vulnerabilities triggered by dynamic code, ie, code generated at runtime by the JIT compiler. The purpose is to help assess the severity of vulnerabilities and thereby assist with vulnerability triage. The framework consists of two components: the first extracts high-level representations of exploitation primitives from existing exploits, and the second uses the primitives so extracted to construct exploits for new bugs. We are currently building a prototype implementation of the framework focusing on JavaScript JIT compilers. To the best of our knowledge, this is the first proposal to consider automatic exploit generation for code generated dynamically by JIT compilers. 

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