From 1d24eb2d536ba27ef938a6563ac8bfb49c738cc1 Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Thu, 6 Jul 2023 09:46:15 +0000 Subject: rust: delete `ForeignOwnable::borrow_mut` We discovered that the current design of `borrow_mut` is problematic. This patch removes it until a better solution can be found. Specifically, the current design gives you access to a `&mut T`, which lets you change where the `ForeignOwnable` points (e.g., with `core::mem::swap`). No upcoming user of this API intended to make that possible, making all of them unsound. Signed-off-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Benno Lossin Reviewed-by: Martin Rodriguez Reboredo Fixes: 0fc4424d24a2 ("rust: types: introduce `ForeignOwnable`") Link: https://lore.kernel.org/r/20230706094615.3080784-1-aliceryhl@google.com Signed-off-by: Miguel Ojeda --- rust/kernel/sync/arc.rs | 3 +-- rust/kernel/types.rs | 22 ++-------------------- 2 files changed, 3 insertions(+), 22 deletions(-) (limited to 'rust') diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index a89843cacaad..172f563976a9 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -243,8 +243,7 @@ impl ForeignOwnable for Arc { let inner = NonNull::new(ptr as *mut ArcInner).unwrap(); // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive - // for the lifetime of the returned value. Additionally, the safety requirements of - // `ForeignOwnable::borrow_mut` ensure that no new mutable references are created. + // for the lifetime of the returned value. unsafe { ArcBorrow::new(inner) } } diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 1e5380b16ed5..d479f8da8f38 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -35,34 +35,16 @@ pub trait ForeignOwnable: Sized { /// /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. - /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow_mut`] - /// for this object must have been dropped. unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Self::Borrowed<'a>; - /// Mutably borrows a foreign-owned object. - /// - /// # Safety - /// - /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for - /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. - /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and - /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped. - unsafe fn borrow_mut(ptr: *const core::ffi::c_void) -> ScopeGuard { - // SAFETY: The safety requirements ensure that `ptr` came from a previous call to - // `into_foreign`. - ScopeGuard::new_with_data(unsafe { Self::from_foreign(ptr) }, |d| { - d.into_foreign(); - }) - } - /// Converts a foreign-owned object back to a Rust-owned one. /// /// # Safety /// /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. - /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and - /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped. + /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] for + /// this object must have been dropped. unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self; } -- cgit v1.2.3