tokio::io::ReadHalf<T>::unsplit can violate the
The soundness issue is described in the tokio/issues#5372
Specific set of conditions needed to trigger an issue (a !Unpin type in ReadHalf)
is unusual, combined with the difficulty of making any arbitrary use-after-free
exploitable in Rust without doing a lot of careful alignment of data types in
the surrounding code.
io-util is also required to be enabled to trigger this
Thanks to zachs18 reporting the issue to Tokio team responsibly and taiki-e
and carllerche appropriately responding and fixing the soundness bug.
Tokio before 0.2.0 used
futures 0.1 that did not have
Pin, so it is not
affected by this issue.