require PyCFunction::new_closure closures to be Sync#6096
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Wow, I hadn't noticed that we had violated this bound within our own test suite 😬 |
Tpt
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This was referenced Jun 12, 2026
RUSTSEC-2026-0177: Missing
Sync bound on PyCFunction::new_closure closures
mihai-dinculescu/tapo#580
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This was referenced Jun 12, 2026
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) (#115) Two RUSTSEC advisories published 2026-06-11 against pyo3 0.28.x, both fixed in 0.29.0: - RUSTSEC-2026-0176 — out-of-bounds read (memory exposure) in BoundListIterator/BoundTupleIterator nth/nth_back (PyO3/pyo3#6086) - RUSTSEC-2026-0177 — missing Sync bound on PyCFunction::new_closure closures (PyO3/pyo3#6096) mkui-py calls none of the affected APIs, so this is a pure dependency bump with no source changes. Version lives in [workspace.dependencies]; mkui-py consumes it via { workspace = true }. Verified locally: - cargo deny check advisories — ok (both IDs resolved) - cargo audit — no vulnerabilities - cargo test -p mkui-py --no-default-features --features parity-test,console — pass - cargo fmt/clippy/test/doc/release — all green - no new transitive deps, no MSRV change (0.29 needs 1.63; workspace is 1.87) Closes #114 Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
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It turns out that
PyCFunction::new_closurehas a thread-safety bug - the closure is not required to beSync. This is worse under the free-threaded build, but also a problem under the GIL-enabled build because of the existence ofPython::detach()allowing the closure to do work without synchronization.I think this is worth reporting to the RustSec Advisory Database; it is possible that existing user code is affected and subtly broken.
I couldn't think of a way to test for this other than UI tests.
(Credit to Claude for the discovery.)