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Sashiko AI review found 1 potential iss= ue(s) to consider: >> >> Pre-existing issues: >> - [High] `Guard::store` temporarily drops the exclusive lock, violating = `Guard` mutual exclusion semantics. >> -- >> >> commit dd1e562319819f32e9d1d6de7db886673c5422d7 >> Author: Andreas Hindborg >> >> rust: xarray: minor formatting fixes >> >> Fix formatting in xarray module to comply with kernel coding guidelines. >> >>> diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs >>> index 46e5f43223fe8..b80fb7a262d0c 100644 >>> --- a/rust/kernel/xarray.rs >>> +++ b/rust/kernel/xarray.rs >> >> [ ... ] >> >>> @@ -44,7 +63,10 @@ >>> /// *guard.get_mut(0).unwrap() =3D 0xffff; >>> /// assert_eq!(guard.get(0).copied(), Some(0xffff)); >>> /// >>> -/// assert_eq!(guard.store(0, beef, GFP_KERNEL)?.as_deref().copied(), = Some(0xffff)); >>> +/// assert_eq!( >>> +/// guard.store(0, beef, GFP_KERNEL)?.as_deref().copied(), >>> +/// Some(0xffff) >>> +/// ); >> >> [Severity: High] >> This isn't a bug introduced by this patch, but since Guard::store calls >> __xa_store which explicitly drops the xa_lock to allocate memory if call= ed >> with blocking flags (like GFP_KERNEL here), doesn't this violate the exp= ected >> mutual exclusion guarantee of the Guard? >> >> In Rust, a lock guard is fundamentally expected to provide strict, conti= nuous >> mutual exclusion for its entire lifetime. Temporarily releasing the lock= while >> a Guard is held breaks this invariant. Any caller relying on the Guard t= o >> ensure atomicity (such as check-and-update patterns) will be exposed to = silent >> Time-Of-Check to Time-Of-Use (TOCTOU) race conditions, as other threads = can >> mutate the array while the lock is dropped. > > Should we rename `Guard` to something else to clarify this, or do you > think it is enough with added documentation on `Guard`? It's fine. `MutexGuard::unlocked` exist for parking-lot crate, it's not tha= t we're introducing a new concept here. Documentation is sufficient. Best, Gary > > > Best regards, > Andreas Hindborg