Unsafe code in CpumaskVar's methods assumes that the type has the same
layout as `bindings::cpumask_var_t`. This is not guaranteed by
the default struct representation in Rust, but requires specifying the
`transparent` representation.

Fixes: 8961b8cb3099a ("rust: cpumask: Add initial abstractions")
Cc: stable@vger.kernel.org
Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
---
 rust/kernel/cpumask.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
index 3fcbff438670..05e1c882404e 100644
--- a/rust/kernel/cpumask.rs
+++ b/rust/kernel/cpumask.rs
@@ -212,6 +212,7 @@ pub fn copy(&self, dstp: &mut Self) {
 /// }
 /// assert_eq!(mask2.weight(), count);
 /// ```
+#[repr(transparent)]
 pub struct CpumaskVar {
     #[cfg(CONFIG_CPUMASK_OFFSTACK)]
     ptr: NonNull<Cpumask>,
-- 
2.43.0

On 12-08-25, 16:42, Baptiste Lepers wrote:
> Unsafe code in CpumaskVar's methods assumes that the type has the same
> layout as `bindings::cpumask_var_t`. This is not guaranteed by
> the default struct representation in Rust, but requires specifying the
> `transparent` representation.
> 
> Fixes: 8961b8cb3099a ("rust: cpumask: Add initial abstractions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
> ---
>  rust/kernel/cpumask.rs | 1 +
>  1 file changed, 1 insertion(+)

Applied. Thanks.

-- 
viresh

On Tue, Aug 12, 2025 at 4:42 PM Baptiste Lepers
<baptiste.lepers@gmail.com> wrote:
>
> Unsafe code in CpumaskVar's methods assumes that the type has the same
> layout as `bindings::cpumask_var_t`. This is not guaranteed by
> the default struct representation in Rust, but requires specifying the
> `transparent` representation.
>
> Fixes: 8961b8cb3099a ("rust: cpumask: Add initial abstractions")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>

Only during CONFIG_CPUMASK_OFFSTACK=n, but yes.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>