Re: [PATCH 1/2] rust: lockdep: Remove support for dynamically allocated LockClassKeys

Dirk Behme
2024-10-05T06:10:24Z

Am 05.10.24 um 00:01 schrieb Mitchell Levy via B4 Relay:
> From: Mitchell Levy <levymitchell0@gmail.com>
>
> Currently, dynamically allocated LockCLassKeys can be used from the Rust
> side without having them registered. This is a soundness issue, so
> remove them.
>
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Link: https://lore.kernel.org/rust-for-linux/20240815074519.2684107-3-nmi@metaspace.dk/
> Cc: stable@vger.kernel.org
> Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
> ---
> rust/kernel/lib.rs | 2 +-
> rust/kernel/sync.rs | 14 ++------------
> 2 files changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 22a3bfa5a9e9..b5f4b3ce6b48 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -44,8 +44,8 @@
> pub mod page;
> pub mod prelude;
> pub mod print;
> -pub mod sizes;
> pub mod rbtree;
> +pub mod sizes;
> mod static_assert;
> #[doc(hidden)]
> pub mod std_vendor;

This is fixed already

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/rust/kernel/lib.rs?id=ece207a83e464af710d641f29e32b7a144c48e79

and can be dropped here.

> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 0ab20975a3b5..d270db9b9894 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -27,28 +27,18 @@
> unsafe impl Sync for LockClassKey {}
>
> impl LockClassKey {
> - /// Creates a new lock class key.
> - pub const fn new() -> Self {
> - Self(Opaque::uninit())
> - }
> -
> pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
> self.0.get()
> }
> }
>
> -impl Default for LockClassKey {
> - fn default() -> Self {
> - Self::new()
> - }
> -}
> -
> /// Defines a new static lock class and returns a pointer to it.
> #[doc(hidden)]
> #[macro_export]
> macro_rules! static_lock_class {
> () => {{
> - static CLASS: $crate::sync::LockClassKey = $crate::sync::LockClassKey::new();

Should the SAFETY comment added in the 2nd patch go to here?

+ // SAFETY: lockdep expects uninitialized memory when it's
handed a statically allocated
+ // lock_class_key

> + static CLASS: $crate::sync::LockClassKey =
> + unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
> &CLASS
> }};
> }
>