On 9/17/26 7:43 PM, Priya Bala Govindasamy wrote:
> The `set_param` function casts `kernel_param.arg` to `*const SetOnce<T>`
> But the Rust module macro in rust/macros/module.rs initializes `arg` with
> `#param_name.as_void_ptr()`, and `#param_name` is a `ModuleParamAccess<T>`,
> not a `SetOnce<T>`.
>
> ModuleParamAccess<T> has default Rust layout but `set_param` accesses its
> first field SetOnce<T> assuming it to be at offset 0. This is not
> guaranteed by Rust and could cause type confusion leading to data
> corruption.
>
> Fix this by casting `kernel_param.arg` to `ModuleParamAccess<T>` and
> then accessing the `value: SetOnce<T>` field.
>
> Fixes: 0b08fc292842 ("rust: introduce module_param module")
> Reported-by: Dylan Zueck <[email protected]>
> Assisted-by: LLM
> Signed-off-by: Priya Bala Govindasamy <[email protected]>
> ---
> rust/kernel/module_param.rs | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/module_param.rs b/rust/kernel/module_param.rs
> index f9a14765a926..7ae87ffe1d6b 100644
> --- a/rust/kernel/module_param.rs
> +++ b/rust/kernel/module_param.rs
> @@ -75,7 +75,9 @@ pub trait ModuleParam: Sized + Copy {
> let new_value = T::try_from_param_arg(arg)?;
>
> // SAFETY: By function safety requirements, this access is safe.
> - let container = unsafe {
> &*((*param).__bindgen_anon_1.arg.cast::<SetOnce<T>>()) };
> + let param_access = unsafe { &*((*param)
> + .__bindgen_anon_1.arg.cast::<ModuleParamAccess<T>>()) };
> + let container = ¶m_access.value;
>
> container
> .populate(new_value)
This looks ok to me, except for the formatting. I plan to take it on the
modules tree, after giving others a bit more time to potentially
comment.
Reviewed-by: Petr Pavlu <[email protected]>
--
Thanks,
Petr
