rust: module_param: Fix potentially incorrect access of `SetOnce<T>`

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")
Cc: stable@vger.kernel.org
Reported-by: Dylan Zueck <dzueck@uci.edu>
Assisted-by: LLM
Suggested-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Priya Bala Govindasamy <pgovind2@uci.edu>
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

0 files changed, 0 insertions, 0 deletions