Double free from safe code when dropping a cloned Handle

[Ollie-Pearce]

Handle derives Clone, which bitwise-copies its pointer field. The Drop implementation for Handle frees the pointee unconditionally, so cloning an instance of Handle and dropping both copies causes a double-free.

#[derive(Clone)]
pub struct Handle {
    handle: *mut pcap_sys::pcap_t,
    live_capture: bool,
    interrupted: std::sync::Arc<std::sync::Mutex<bool>>,
}

impl Drop for Handle {
    fn drop(&mut self) {
        self.close();
    }
}

Reproducing:

use pcap_async::Handle;

#[test]
fn handle_double_free() {
    let foo = Handle::dead(0, 0).unwrap();
    let bar: Handle = (*foo).clone();

    drop(bar); // pcap_close(handle)
    drop(foo); // SAME pcap_t, closed again
}

You can run the above test with valgrind and see an Invalid read error.

cargo test --test repro --no-run
valgrind --leak-check=no ./target/debug/deps/repro-<HASH>

Fix:

• Drop #[derive(Clone)] on Handle.