Reported

January 24, 2022

Issued

January 24, 2022 (last modified: June 13, 2023)

Package

qcell (crates.io)

Type

INFO Unsound

Keywords

#unsound

Aliases

• GHSA-9c9f-7x9p-4wqp

References

• https://github.com/uazu/qcell/issues/20

Patched

• >=0.4.3

Description

This is impossible to do by accident, but by carefully constructing marker types to be covariant, a malicious coder can cheat the singleton check in TCellOwner and TLCellOwner, giving unsound access to cell memory. This could take the form of getting two mutable references to the same memory, or a mutable reference and an immutable reference.

The fix is for the crate to internally force the marker type to be invariant. This blocks the conversion between covariant types which Rust normally allows.

Advisory available under CC0-1.0 license.