Re: [PATCH v6 4/7] rust: id_pool: add contiguous area allocation

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] `IdPool::alloc_area` panics under `CONFIG_RUST_BITMAP_HARDENED` when `offset >= capacity()` instead of returning `None` to trigger dynamic growth
--

--- Patch [4]: [PATCH v6 4/7] rust: id_pool: add contiguous area allocation ---
commit 8aa0c8588b18c055db8bdd7090bd5d9190acf589
Author: Eliot Courtney <[email protected]>

rust: id_pool: add contiguous area allocation

Add IdPool::alloc_area which allocates a contiguous area with the
given offset, count, and alignment.

> diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
> index 384753fe0e44a..a4a2ff417fe81 100644
> --- a/rust/kernel/id_pool.rs
> +++ b/rust/kernel/id_pool.rs
[ ... ]
> @@ -240,6 +246,32 @@ pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> {
>      pub fn release_id(&mut self, id: usize) {
>          self.map.clear_bit(id);
>      }
> +
> +    /// Allocates a contiguous area of `count` IDs at or after `offset`.
> +    ///
> +    /// The start of the returned area is a multiple of `align`.
> +    ///
> +    /// Returns the allocated range upon success, or [`None`] if no such area could be found.
> +    #[inline]
> +    #[must_use]
> +    pub fn alloc_area(
> +        &mut self,
> +        offset: usize,
> +        count: NonZero<usize>,
> +        align: Alignment,
> +    ) -> Option<Range<usize>> {

[Severity: High]
Does this panic under CONFIG_RUST_BITMAP_HARDENED if offset is greater than
or equal to the pool's capacity?

When offset is passed directly to BitmapVec::next_zero_area(), the hardened
build of the bitmap operations will assert that the start offset is less
than the length.

If a caller dynamically searches for contiguous areas and their sliding window
goes beyond the current capacity, could this crash the kernel rather than
safely returning None to trigger a dynamic growth request?

> +        let start = self.map.next_zero_area(offset, count, align)?;
> +        self.map.set(start, count);
> +        Some(start..start + count.get())
> +    }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4