GitLab

Hi there, we (Rust group @sslab-gatech) are scanning crates on crates.io for potential soundness bugs. We noticed that World implements Send without any bounds on the EntityStore and ComponentStore.

https://gitlab.redox-os.org/redox-os/dces-rust/-/blob/develop/src/world.rs#L37-42

unsafe impl<E, C, Ctx> Send for World<E, C, Ctx>
where
    E: EntityStore,
    C: ComponentStore
{
}

We think this should be EntityStore + Send and ComponentStore + Send, otherwise it's possible to send non-Send types across thread boundaries as part of the world. Here's an example with an EntityStore that uses an Rc causing a segfault from safe rust code:

#![forbid(unsafe_code)]

use dces::prelude::*;
use dces::entity::EntityStore;

use std::rc::Rc;

struct MyEntityStore {
    entity_store_rc: Rc<i32>
}

impl EntityStore for MyEntityStore {
    fn register_entity(&mut self, entity: impl Into<Entity>) {
        println!("Thread: {:p}", self.entity_store_rc);
        // Races with the Rc in the main thread.
        for _ in 0..100_000_000 {
            self.entity_store_rc.clone();
        }
    }

    fn remove_entity(&mut self, entity: impl Into<Entity>) { }
}

fn main() {
    let rc = Rc::new(42);

    let entity_store = MyEntityStore { entity_store_rc: rc.clone() };
    let mut world = World::from_stores(entity_store, ComponentStore::default());

    std::thread::spawn(move || {
        world.create_entity().build();
    });

    println!("Main:   {:p}", rc);
    for _ in 0..100_000_000 {
        rc.clone();
    }
}

Output:

Main:   0x562f05d16b50
Thread: 0x562f05d16b50

Terminated with signal 4 (SIGILL)