linux-kernel - [PATCH] rust: devres: initialize Devres::inner::data last

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Message-ID: <20250714113712.22158-1-dakr@kernel.org>
Date: Mon, 14 Jul 2025 13:32:35 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	daniel.almeida@...labora.com,
	m.wilczynski@...sung.com
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH] rust: devres: initialize Devres::inner::data last

Users may want to access the Devres object from callbacks registered
through the initialization of Devres::inner::data.

For those accesses to be valid, Devres::inner::data must be initialized
last [1].

Credit to Boqun for spotting this [2].

Link: https://lore.kernel.org/lkml/DBBPHO26CPBS.2OVI1OERCB2J5@kernel.org/ [1]
Link: https://lore.kernel.org/lkml/aHSmxWeIy3L-AKIV@Mac.home/ [2]
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/devres.rs | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index a8a2d24cac24..152a89b78943 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -137,14 +137,10 @@ pub fn new<'a, E>(
         let callback = Self::devres_callback;
 
         try_pin_init!(&this in Self {
-            // INVARIANT: `inner` is properly initialized.
-            inner <- Opaque::pin_init(try_pin_init!(Inner {
-                data <- Revocable::new(data),
-                devm <- Completion::new(),
-                revoke <- Completion::new(),
-            })),
+            dev: dev.into(),
             callback,
-            dev: {
+            // INVARIANT: `inner` is properly initialized.
+            inner <- {
                 // SAFETY: `this` is a valid pointer to uninitialized memory.
                 let inner = unsafe { &raw mut (*this.as_ptr()).inner };
 
@@ -158,7 +154,11 @@ pub fn new<'a, E>(
                     bindings::devm_add_action(dev.as_raw(), Some(callback), inner.cast())
                 })?;
 
-                dev.into()
+                Opaque::pin_init(try_pin_init!(Inner {
+                    devm <- Completion::new(),
+                    revoke <- Completion::new(),
+                    data <- Revocable::new(data),
+                }))
             },
         })
     }

base-commit: 3964d07dd821efe9680e90c51c86661a98e60a0f
prerequisite-patch-id: 12a88f7c46bec668e4f71ec0d94b1782d9446d0b
-- 
2.50.0