Merge pull request #473 from LeSeulArtichaut/unsafe-ptr-container-of

Don't hide unsafety in `$ptr` argument of `container_of!`

Author: ojeda

rust/kernel/lib.rs

@@ -220,7 +220,8 @@ macro_rules! offset_of {
 #[macro_export]
 macro_rules! container_of {
     ($ptr:expr, $type:ty, $($f:tt)*) => {{
+        let ptr = $ptr as *const _ as *const u8;
         let offset = $crate::offset_of!($type, $($f)*);
-        unsafe { ($ptr as *const _ as *const u8).offset(-offset) as *const $type }
+        unsafe { ptr.offset(-offset) as *const $type }
     }}
 }

rust/kernel/miscdev.rs

@@ -85,10 +85,8 @@ impl<T: Sync> FileOpenAdapter for Registration<T> {
     type Arg = T;
 
     unsafe fn convert(_inode: *mut bindings::inode, file: *mut bindings::file) -> *const Self::Arg {
-        // TODO: `SAFETY` comment required here even if `unsafe` is not present,
-        // because `container_of!` hides it. Ideally we would not allow
-        // `unsafe` code as parameters to macros.
-        let reg = crate::container_of!((*file).private_data, Self, mdev);
+        // SAFETY: the caller must guarantee that `file` is valid.
+        let reg = crate::container_of!(unsafe { (*file).private_data }, Self, mdev);
         unsafe { &(*reg).context }
     }
 }