Re: [PATCH] rust: num: seal Integer

[Gary Guo]

On Sat Sep 5, 2026 at 3:17 AM BST, Younes Akhouayri via B4 Relay wrote:
> From: Younes Akhouayri <git@xxxxxxxxx>
>
> Bounded relies on Integer implementations to describe primitive integer
> semantics correctly. In particular, it uses Integer::BITS and Signedness
> to justify unchecked operations.
>
> Integer is currently safe and externally implementable, so an
> implementation can violate those assumptions and make safe Bounded
> operations reach undefined behavior.
>
> Seal Integer so only the primitive implementations provided by the
> kernel crate can satisfy it.
>
> Fixes: 01e345e82ec3 ("rust: num: add Bounded integer wrapping type")
> Closes: https://lore.kernel.org/rust-for-linux/CANiq72mOfR33s4y+Ueivd5NrC5yre+Pcp57ZOBz0msw9A4AP1Q@xxxxxxxxxxxxxx/
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Signed-off-by: Younes Akhouayri <git@xxxxxxxxx>
> ---
>  rust/kernel/num.rs | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/num.rs b/rust/kernel/num.rs
> index dbe848e30efe..de589792a77a 100644
> --- a/rust/kernel/num.rs
> +++ b/rust/kernel/num.rs
> @@ -15,9 +15,14 @@ pub enum Unsigned {}
>  /// Designates signed primitive types.
>  pub enum Signed {}
>  
> +mod private {
> +    pub trait Sealed {}
> +}

I feel that it's time to add an attribute macro for sealing.

Yes, more macros :)

Best,
Gary

> +
>  /// Describes core properties of integer types.
>  pub trait Integer:
> -    Sized
> +    private::Sealed
> +    + Sized
>      + Copy
>      + Clone
>      + PartialEq
> @@ -56,6 +61,8 @@ pub trait Integer:
>  macro_rules! impl_integer {
>      ($($type:ty: $signedness:ty), *) => {
>          $(
> +        impl private::Sealed for $type {}
> +
>          impl Integer for $type {
>              type Signedness = $signedness;
>  
>
> ---
> base-commit: e510334fbaeaa016ac76d80b4c5f47611c5f7860
> change-id: 20260903-feature-rust-num-seal-integer-a4262df429c6
>
> Best regards,
> --  
> Younes Akhouayri <git@xxxxxxxxx>