Reported

January 11, 2023

Issued

February 2, 2023

Package

tokio (crates.io)

Type

INFO Unsound

Categories

• memory-exposure

Details

https://github.com/tokio-rs/tokio/issues/5372

Patched

• >=1.18.5, <1.19.0
• >=1.20.4, <1.21.0
• >=1.24.2

Unaffected

• <0.2.0

Description

tokio::io::ReadHalf<T>::unsplit can violate the Pin contract

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.

The tokio feature io-util is also required to be enabled to trigger this soundness issue.

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.