Fast Summary-based Whole-program Analysis to Identify Unsafe Memory Accesses in Rust

Abstract: Rust is one of the most promising systems programming languages to fundamentally solve the memory safety issues that have plagued low-level software for over forty years. However, to accommodate the scenarios where Rust's type rules might be too restrictive for certain systems programming and where programmers opt for performance over security checks, Rust opens security escape hatches allowing writing unsafe source code or calling unsafe libraries. Consequently, unsafe Rust code and directly-linked unsafe foreign libraries may not only introduce memory safety violations themselves but also compromise the entire program as they run in the same monolithic address space as the safe Rust. This problem can be mitigated by isolating unsafe memory objects (those accessed by unsafe code) and sandboxing memory accesses to the unsafe memory. One category of prior work utilizes existing program analysis frameworks on LLVM IR to identify unsafe memory objects and accesses. However, they suffer the limitations of prolonged analysis time and low precision. In this paper, we tackled these two challenges using summary-based whole-program analysis on Rust's MIR. The summary-based analysis computes information on demand so as to save analysis time. Performing analysis on Rust's MIR exploits the rich high-level type information inherent to Rust, which is unavailable in LLVM IR. This manuscript is a preliminary study of ongoing research. We have prototyped a whole-program analysis for identifying both unsafe heap allocations and memory accesses to those unsafe heap objects. We reported the overhead and the efficacy of the analysis in this paper.