rust-sanitizers-miri

Rust Sanitizers and Miri

Purpose

Guide agents through runtime safety validation for Rust: ASan/TSan/MSan/UBSan via RUSTFLAGS, Miri for compile-time UB detection in unsafe code, and interpreting sanitizer reports.

Triggers

• "How do I run AddressSanitizer on Rust code?"
• "How do I use Miri to check my unsafe Rust?"
• "How do I run ThreadSanitizer on a Rust program?"
• "My unsafe Rust might have UB — how do I detect it?"
• "How do I interpret a Rust ASan report?"
• "Can I run Rust sanitizers on stable?"

Workflow

1. Sanitizers in Rust (nightly required)

Rust sanitizers require nightly and a compatible platform:

# Install nightly
rustup toolchain install nightly
rustup component add rust-src --toolchain nightly

# AddressSanitizer (Linux, macOS)
RUSTFLAGS="-Z sanitizer=address" \
    cargo +nightly test -Zbuild-std \
    --target x86_64-unknown-linux-gnu

# ThreadSanitizer (Linux)
RUSTFLAGS="-Z sanitizer=thread" \
    cargo +nightly test -Zbuild-std \
    --target x86_64-unknown-linux-gnu

# MemorySanitizer (Linux, requires all-instrumented build)
RUSTFLAGS="-Z sanitizer=memory -Zsanitizer-memory-track-origins" \
    cargo +nightly test -Zbuild-std \
    --target x86_64-unknown-linux-gnu

# UndefinedBehaviorSanitizer
RUSTFLAGS="-Z sanitizer=undefined" \
    cargo +nightly test -Zbuild-std \
    --target x86_64-unknown-linux-gnu

-Zbuild-std rebuilds the standard library with the sanitizer, which is necessary for accurate results.

2. Stable sanitizer workaround

For stable Rust, use the cross tool with a Docker image that has sanitizers pre-configured, or run cargo test inside a Docker container with a nightly image.

Alternatively, for simpler UB checking without nightly:

# cargo-sanitize (wrapper)
cargo install cargo-sanitize
cargo sanitize address

3. Interpreting ASan output in Rust

==12345==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000050
READ of size 4 at 0x602000000050 thread T0
    #0 0x401234 in myapp::module::function /src/main.rs:15
    #1 0x401567 in myapp::main /src/main.rs:42

0x602000000050 is located 0 bytes after a 40-byte region allocated at:
    #0 0x... in alloc::alloc::alloc ...
    #1 0x... in myapp::create_buffer /src/main.rs:10