From 47c430e31bac095887f03ade8dac62fb5c70821d Mon Sep 17 00:00:00 2001
From: Baptiste Lepers <baptiste.lepers@gmail.com>
Date: Tue, 12 Aug 2025 15:26:56 +0200
Subject: [PATCH] rust: mm: mark VmaNew as transparent
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commit 5cc5e030bce2ec97ae5cdb2c1b94a98b1047b3fa upstream.

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

Link: https://lkml.kernel.org/r/20250812132712.61007-1-baptiste.lepers@gmail.com
Fixes: dcb81aeab406 ("mm: rust: add VmaNew for f_ops->mmap()")
Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Björn Roy Baron <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Trevor Gross <tmgross@umich.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 rust/kernel/mm/virt.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs
index 31803674aecc..a1181cfae962 100644
--- a/rust/kernel/mm/virt.rs
+++ b/rust/kernel/mm/virt.rs
@@ -209,6 +209,7 @@ impl VmaMixedMap {
 ///
 /// For the duration of 'a, the referenced vma must be undergoing initialization in an
 /// `f_ops->mmap()` hook.
+#[repr(transparent)]
 pub struct VmaNew {
     vma: VmaRef,
 }