rust: file: mark `LocalFile` as `repr(transparent)`

Unsafe code in `LocalFile`'s methods assumes that the type has the same
layout as the inner `bindings::file`. This is not guaranteed by the default
struct representation in Rust, but requires specifying the `transparent`
representation.

The `File` struct (which also wraps `bindings::file`) is already marked as
`repr(transparent)`, so this change makes their layouts equivalent.

Fixes: 851849824bb5 ("rust: file: add Rust abstraction for `struct file`")
Closes: https://github.com/Rust-for-Linux/linux/issues/1165
Signed-off-by: Pekka Ristola <pekkarr@protonmail.com>
Link: https://lore.kernel.org/20250527204636.12573-1-pekkarr@protonmail.com
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 13a0e44cd1aa812eb404d452c076f90a37275b5b..138693bdeb3fdfc4dc9eb9adbf8bfd5809e1596b 100644 (file)
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -219,6 +219,7 @@ unsafe impl AlwaysRefCounted for File {
 ///   must be on the same thread as this file.
 ///
 /// [`assume_no_fdget_pos`]: LocalFile::assume_no_fdget_pos
+#[repr(transparent)]
 pub struct LocalFile {
     inner: Opaque<bindings::file>,
 }