Re: [PATCH v2] rust: id_pool: document panics in `find_unused_id` and `release_id`

[Yury Norov]

On Tue, Sep 08, 2026 at 04:31:57PM -0400, Georgios Androutsopoulos wrote:
> `find_unused_id()` calls `Bitmap::next_zero_bit()` and `release_id()`
> calls `Bitmap::clear_bit()`, both of which panic when
> `CONFIG_RUST_BITMAP_HARDENED` is enabled and the index is out of
> bounds. Neither `IdPool` method documents this.
> 
> Add the missing `# Panics` sections and state the bounds requirement
> on `offset` and `id`.
> 
> Fixes: 2cdae413cd3e ("rust: add dynamic ID pool abstraction for bitmap")
> Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> Signed-off-by: Georgios Androutsopoulos <georgeandrout13@xxxxxxxxx>

Applied both in bitmap-for-next. Thanks!

> ---
> Changes in v2:
> - Use "within bounds" instead of "in bounds", following feedback from
>   Alexandre Courbot.
> - Add Fixes:, treating the documentation hole as a bug [1].
> - Link to v1: https://lore.kernel.org/rust-for-linux/20260829153442.20799-1-georgeandrout13@xxxxxxxxx/
> 
> [1] https://lore.kernel.org/rust-for-linux/CANiq72mgZg-QBy4gwzHmD4gJm4wScktfpdDtyZt3Zijk83h2CA@xxxxxxxxxxxxxx/
> ---
>  rust/kernel/id_pool.rs | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
> index 384753fe0e44..ae6960d7f638 100644
> --- a/rust/kernel/id_pool.rs
> +++ b/rust/kernel/id_pool.rs
> @@ -224,7 +224,13 @@ pub fn grow(&mut self, mut resizer: PoolResizer) {
>      /// Finds an unused ID in the bitmap.
>      ///
>      /// Upon success, returns its index. Otherwise, returns [`None`]
> -    /// to indicate that a [`Self::grow_request`] is needed.
> +    /// to indicate that a [`Self::grow_request`] is needed. `offset` must be
> +    /// within bounds.
> +    ///
> +    /// # Panics
> +    ///
> +    /// Panics if `CONFIG_RUST_BITMAP_HARDENED` is enabled and `offset` is out
> +    /// of bounds.
>      #[inline]
>      #[must_use]
>      pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> {
> @@ -236,6 +242,13 @@ pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> {
>      }
> 
>      /// Releases an ID.
> +    ///
> +    /// The `id` must be within bounds.
> +    ///
> +    /// # Panics
> +    ///
> +    /// Panics if `CONFIG_RUST_BITMAP_HARDENED` is enabled and `id` is out of
> +    /// bounds.
>      #[inline]
>      pub fn release_id(&mut self, id: usize) {
>          self.map.clear_bit(id);
> 
> base-commit: 73e3f0710014fe6d4ed98cfc02292f6121db7558
> --
> 2.47.3