Fix use-after-free due to a lifetime error in Vec::into_iter()

[lamcodeofpwnosec]

Changes in this pull request

In affected versions of this crate, the lifetime of the iterator produced by Vec::into_iter() is not constrained to the lifetime of the Bump that allocated the vector's memory. Using the iterator after the bump is dropped causes use-after-free accesses.

use bumpalo::{collections::Vec, Bump};

fn main() {
    let bump = Bump::new();
    let mut vec = Vec::new_in(&bump);
    vec.extend([0x01u8; 32]);
    let into_iter = vec.into_iter();
    drop(bump);

    for _ in 0..100 {
        let reuse_bump = Bump::new();
        let _reuse_alloc = reuse_bump.alloc([0x41u8; 10]);
    }

    for x in into_iter {
        print!("0x{:02x} ", x);
    }
    println!();
}

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• All applicable changes have been documented
• Any TO DO items (or similar) have been entered as GitHub issues and the link to that issue has been included in a comment