GHSA-rh4w-94hh-9943
MutexGuard::map can cause a data race in safe code
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| crates.io | futures-util | >= 0.3.2, < 0.3.7 | 0.3.7 |
Details
As written in the advisory (Markdown source, shown as plain text).
Affected versions of the crate had a Send/Sync implementation for MappedMutexGuard that only considered variance on T, while MappedMutexGuard dereferenced to U.
This could of led to data races in safe Rust code when a closure used in MutexGuard::map() returns U that is unrelated to T.
The issue was fixed by fixing Send and Sync implementations, and by adding a PhantomData<&'a mut U> marker to the MappedMutexGuard type to tell the compiler that the guard is over U too.
References
External links from the advisory. They lead to third-party sites.