Incompatible ASan runtimes when Rust executable links with C shared library that dynamic links asan runtime

[hehaoqian]

Issues:

1. Address sanitized Rust program can compile, but fails to run,
   when it links a shared library that dynamic links to libasan.so,
   which is provided by gcc 7.5
2. The error message is

==82818==Your application is linked against incompatible ASan runtimes.

3. It can run with expected result if the shared lib static links to asan runtime, by -static-libasan in C link flags

---

The cause:

1. When using RUSTFLAGS=-Zsanitizer=address, it seems rustc always static links asan runtime,
   by static link librustc-nightly_rt.asan.a bundled with rustc installation
2. I think static links libasan, is not compatible with dynamic linked libasan
3. I don't think rustc provides a way to opt out of static linking librustc-nightly_rt.asan.a

---

Compatibility of asan runtimes of gcc7.5.0 and rustc

1. The version of asan in gcc7.5.0 is 8
   According to __asan_version_mismatch_check_v8 in https://github.com/gcc-mirror/gcc/blob/releases/gcc-7.5.0/libsanitizer/asan/asan_init_version.h
2. The version of asan in rustc is also 8.
   According to GetAsanVersion function in https://github.com/rust-lang/llvm-project/blob/rustc/16.0-2023-06-05/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

---

Steps to reproduce

// segfault.c
int segfault(void) {
        return *(int *)0x41414141;
}

Create C shared lib by gcc -shared -fPIC segfault.c -o libsegfault.so -fsanitize=address

// build.rs
fn main() {
    println!("cargo:rustc-link-search=.");
    println!("cargo:rustc-link-lib=segfault");
}

// src/main.rs
extern "C" {
    fn segfault() -> i32;
}
fn main() {
    println!("Hello world!");
    unsafe { segfault() };
}

Producing Rust executable with

RUSTFLAGS="-Z sanitizer=address"  cargo +nightly build -Z build-std

Then run the final executable, set environment variable LD_LIBRARY_PATH if needed

---

Actual result:

==82818==Your application is linked against incompatible ASan runtimes.

Expected result:

==108960==ERROR: AddressSanitizer: SEGV on unknown address 0x000041414141 

---

Meta

Target platform: x86_64-unknown-linux-gnu

rustc --version --verbose:

rustc 1.73.0-nightly (399b06823 2023-07-20)

gcc --version

gcc (GCC) 7.5.0

---

Extra notes:

I asked ChatGPT

gcc address sanitizer, shared link or static link?

It answers:

When using the GCC (GNU Compiler Collection) AddressSanitizer (ASan),
it is generally recommended to use it with shared libraries (dynamic linking) rather than static linking.
AddressSanitizer is a powerful runtime memory error detector that can find various memory-related issues like out-of-bounds access, use-after-free, and memory leaks.

[ObsidianMinor]

I'm also encountering this issue. We're trying to link to C++ (clang) that's instrumented for ASAN, but Rust's custom ASAN library doesn't include CXX compiler runtime features. So linking fails for missing symbols. We can't dynamically link the C++ code to ASAN either because both will have duplicate symbols. If you ignore the duplicate symbols weird things happen if you try to build a Rust binary. We need a way to tell rustc to not link it's ASAN library so we can link in our own through another linker flag.

[ObsidianMinor]

Actually it turns out this has been fixed recently with #121207. Now you can avoid linking librustc-nightly_rt.asan.a. Might fix this case too.

[rcvalle]

This seems to have been fixed in #121207. Closing.