An issue was discovered in the signal-simple crate through 2020-11-15 for Rust. There are unconditional implementations of Send and Sync for SyncChannel<T>.

Affected: crates.io: signal-simple

Affected versions of this crate unconditionally implement Send/Sync for SyncChannel<T>. SyncChannel<T> doesn't provide access to &T but merely serves as a channel that consumes and returns owned T.

Users can create UB in safe Rust by sending T: !Send to other threads with SyncChannel::send/recv APIs. Using T = Arc<Cell<_> allows to create data races (which can lead to memory corruption), and using T = MutexGuard<T> allows to unlock a mutex from a thread that didn't lock the mutex.

Affected: crates.io: signal-simple

Affected versions of this crate unconditionally implement Send/Sync for `SyncChannel<T>`. `SyncChannel<T>` doesn't provide access to `&T` but merely serves as a channel that consumes and returns owned `T`.

Users can create UB in safe Rust by sending `T: !Send` to other threads with `SyncChannel::send/recv` APIs. Using `T = Arc<Cell<_>` allows to create data races (which can lead to memory corruption), and using `T = MutexGuard<T>` allows to unlock a mutex from a thread that didn't lock the mutex.