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RUSTSEC-2026-0386: `AsyncFd::new` and related constructors violate I/O safety

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Evaluación

Dificultad
1/5
Tiempo estimado
Menos de una hora
Aptitud para principiantes
15/100
Tipo de issue
Error
Claridad
Necesita aclaración
Estado de actividad
Activo
Stack tecnológico
rust, wasm
Área
backend, security

Línea de trabajo

The issue describes an unsoundness report in Tokio's AsyncFd constructors, but does not identify any Wasmtime files or tests to change. Start by reading the linked Tokio pull request and advisory, then check whether Wasmtime uses the affected constructors. Done looks like a scoped response to the report based on that investigation.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

AsyncFd::new and related constructors violate I/O safety

Details
Status unsound
Package tokio
Version 1.51.1
URL https://github.com/tokio-rs/tokio/pull/8587
Date 2026-10-13

tokio::io::unix::AsyncFd provides safe constructors (new, with_interest, try_new, and try_with_interest) that accept any T: AsRawFd rather than requiring proof of ownership or validity of the file descriptor. Because RawFd implements AsRawFd, safe code can construct an AsyncFd from an arbitrary or closed file descriptor, or close/replace the underlying file descriptor while the AsyncFd is still alive.

This violates I/O safety in two ways:

  1. AsyncFd<T> implements AsFd for all T: AsRawFd by calling BorrowedFd::borrow_raw(self.as_raw_fd()), allowing safe code to obtain an arbitrary BorrowedFd<'_> without owning the file descriptor.
  2. Tokio's I/O driver stores a pointer to an internal allocation in the epoll/kqueue user data for registered file descriptors. If the underlying file descriptor is duplicated and then closed while an AsyncFd is alive, and the OS reuses that file descriptor number for a another IO resource on the same runtime, dropping the first AsyncFd deregisters the reused file descriptor number and frees the first while the original file description remains registered in epoll, leading to a use-after-free when a readiness event fires.

Starting in Tokio 1.51.6, 1.53.3, and 1.54.0, AsyncFd::new, AsyncFd::with_interest, AsyncFd::try_new, and AsyncFd::try_with_interest are deprecated in favor of the unsafe constructors AsyncFd::register and AsyncFd::register_with_interest. Callers must ensure that the file descriptor remains valid, open, and unchanged for the lifetime of the AsyncFd.

See advisory page for additional details.

Lenguaje dominante
Rust
Estrellas
18.7k
Forks
1.9k
Merge medio
1 d 15 min
PR fusionados (30 d)
379

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  4. Abre un pull request que haga referencia al número del issue.

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