[v2,1/2] rust: lockdep: Remove support for dynamically allocated LockClassKeys

Commit Message

Mitchell Levy Dec. 19, 2024, 8:58 p.m. UTC

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 <[e-mail]>
Link: https://lore.kernel.org/rust-for-linux/[e-mail]/
Cc: [e-mail]
Signed-off-by: Mitchell Levy <[e-mail]>
---
 rust/kernel/sync.rs | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

Patch

diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 1eab7ebf25fd..ae16bfd98de2 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -29,28 +29,20 @@ 
 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();
+        // 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
     }};
 }