diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index d479f8da8f38..1c2fb36906b6 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -20,66 +20,111 @@
 /// This trait is meant to be used in cases when Rust objects are stored in C objects and
 /// eventually "freed" back to Rust.
 pub trait ForeignOwnable: Sized {
-    /// Type of values borrowed between calls to [`ForeignOwnable::into_foreign`] and
-    /// [`ForeignOwnable::from_foreign`].
+    /// Type used to immutably borrow a value that is currently foreign-owned.
     type Borrowed<'a>;
 
+    /// Type used to mutably borrow a value that is currently foreign-owned.
+    type BorrowedMut<'a>;
+
     /// Converts a Rust-owned object to a foreign-owned one.
     ///
     /// The foreign representation is a pointer to void.
     fn into_foreign(self) -> *const core::ffi::c_void;
 
-    /// 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.
-    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Self::Borrowed<'a>;
-
     /// 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`] for
-    /// this object must have been dropped.
+    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and it
+    /// must not be passed to `from_foreign` more than once.
+    ///
+    /// [`into_foreign`]: Self::into_foreign
     unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self;
+
+    /// Borrows a foreign-owned object immutably.
+    ///
+    /// This method provides a way to access a foreign-owned value from Rust immutably. It provides
+    /// you with exactly the same abilities as an `&Self` when the value is Rust-owned.
+    ///
+    /// # Safety
+    ///
+    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and if
+    /// the pointer is ever passed to [`from_foreign`], then that call must happen after the end of
+    /// the lifetime 'a.
+    ///
+    /// [`into_foreign`]: Self::into_foreign
+    /// [`from_foreign`]: Self::from_foreign
+    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Self::Borrowed<'a>;
+
+    /// Borrows a foreign-owned object mutably.
+    ///
+    /// This method provides a way to access a foreign-owned value from Rust mutably. It provides
+    /// you with exactly the same abilities as an `&mut Self` when the value is Rust-owned, except
+    /// that this method does not let you swap the foreign-owned object for another. (That is, it
+    /// does not let you change the address of the void pointer that the foreign code is storing.)
+    ///
+    /// Note that for types like [`Arc`], an `&mut Arc<T>` only gives you immutable access to the
+    /// inner value, so this method also only provides immutable access in that case.
+    ///
+    /// In the case of `Box<T>`, this method gives you the ability to modify the inner `T`, but it
+    /// does not let you change the box itself. That is, you cannot change which allocation the box
+    /// points at.
+    ///
+    /// # Safety
+    ///
+    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and if
+    /// the pointer is ever passed to [`from_foreign`], then that call must happen after the end of
+    /// the lifetime 'a.
+    ///
+    /// The lifetime 'a must not overlap with the lifetime of any other call to [`borrow`] or
+    /// `borrow_mut` on the same object.
+    ///
+    /// [`into_foreign`]: Self::into_foreign
+    /// [`from_foreign`]: Self::from_foreign
+    /// [`borrow`]: Self::borrow
+    /// [`Arc`]: crate::sync::Arc
+    unsafe fn borrow_mut<'a>(ptr: *const core::ffi::c_void) -> Self::BorrowedMut<'a>;
 }
 
 impl<T: 'static> ForeignOwnable for Box<T> {
     type Borrowed<'a> = &'a T;
+    type BorrowedMut<'a> = &'a mut T;
 
     fn into_foreign(self) -> *const core::ffi::c_void {
         Box::into_raw(self) as _
     }
 
-    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> &'a T {
-        // SAFETY: The safety requirements for this function ensure that the object is still alive,
-        // so it is safe to dereference the raw pointer.
-        // The safety requirements of `from_foreign` also ensure that the object remains alive for
-        // the lifetime of the returned value.
-        unsafe { &*ptr.cast() }
-    }
-
     unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self {
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
         unsafe { Box::from_raw(ptr as _) }
     }
+
+    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> &'a T {
+        // SAFETY: The safety requirements of this method ensure that the object remains alive and
+        // immutable for the duration of 'a.
+        unsafe { &*ptr.cast() }
+    }
+
+    unsafe fn borrow_mut<'a>(ptr: *const core::ffi::c_void) -> &'a mut T {
+        // SAFETY: The safety requirements of this method ensure that the pointer is valid and that
+        // nothing else will access the value for the duration of 'a.
+        unsafe { &mut *ptr.cast_mut().cast() }
+    }
 }
 
 impl ForeignOwnable for () {
     type Borrowed<'a> = ();
+    type BorrowedMut<'a> = ();
 
     fn into_foreign(self) -> *const core::ffi::c_void {
         core::ptr::NonNull::dangling().as_ptr()
     }
 
-    unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {}
-
     unsafe fn from_foreign(_: *const core::ffi::c_void) -> Self {}
+
+    unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {}
+    unsafe fn borrow_mut<'a>(_: *const core::ffi::c_void) -> Self::BorrowedMut<'a> {}
 }
 
 /// Runs a cleanup function/closure when dropped.

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 172f563976a9..f152a562c9c3 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -232,26 +232,35 @@ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
 
 impl<T: 'static> ForeignOwnable for Arc<T> {
     type Borrowed<'a> = ArcBorrow<'a, T>;
+    // Mutable access to the `Arc` does not give any extra abilities over
+    // immutable access.
+    type BorrowedMut<'a> = ArcBorrow<'a, T>;
 
     fn into_foreign(self) -> *const core::ffi::c_void {
         ManuallyDrop::new(self).ptr.as_ptr() as _
     }
 
-    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> {
-        // SAFETY: By the safety requirement of this function, we know that `ptr` came from
-        // a previous call to `Arc::into_foreign`.
-        let inner = NonNull::new(ptr as *mut ArcInner<T>).unwrap();
-
-        // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
-        // for the lifetime of the returned value.
-        unsafe { ArcBorrow::new(inner) }
-    }
-
     unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self {
         // SAFETY: By the safety requirement of this function, we know that `ptr` came from
         // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and
         // holds a reference count increment that is transferrable to us.
-        unsafe { Self::from_inner(NonNull::new(ptr as _).unwrap()) }
+        unsafe { Self::from_inner(NonNull::new_unchecked(ptr as _)) }
     }
+
+    unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> {
+        // SAFETY: By the safety requirement of this function, we know that `ptr` came from
+        // a previous call to `Arc::into_foreign`.
+        let inner = unsafe { NonNull::new_unchecked(ptr as *mut ArcInner<T>) };
+
+        // SAFETY: The safety requirements ensure that we will not give up our
+        // foreign-owned refcount while the `ArcBorrow` is still live.
+        unsafe { ArcBorrow::new(inner) }
+    }
+
+    unsafe fn borrow_mut<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> {
+        // SAFETY: The safety requirements for `borrow_mut` are a superset of the safety
+        // requirements for `borrow`.
+        unsafe { Self::borrow(ptr) }
+    }
 }

