Potentially unsafe usage of Arc::get_mut RS-S1000

In the standard library in Rust before 1.29.0, there is weak synchronization in the Arc::get_mut method. This synchronization issue can be lead to memory safety issues through race conditions.

This bug has since been fixed, consider upgrading to a newer version of Rust to mitigate this issue.

Bad practice

extern crate rayon;

use std::sync::Arc;
use rayon::join;

fn main() {
    let a1 = Arc::new(0);
    let mut a2 = a1.clone();
    join(
        // thread 1
        || {
            let _: u32 = *a1;
            drop(a1);
        },

        // thread 2
        || loop {
            match Arc::get_mut(&mut a2) {
                None => {}
                Some(m) => {
                    *m = 1u32;
                    return;
                }
            }
        },
    );
}

The above code sample results in a data race, between a read in the first thread and a write in the second thread, because Arc::get_mut only uses a relaxed read of the strong counter.

References

• CVE-2018-25008