linux-kernel - [PATCH] rust: devres: fix leaking call to devm_add

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Message-ID: <20250811214619.29166-1-dakr@kernel.org>
Date: Mon, 11 Aug 2025 23:44:48 +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
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>,
	stable@...r.kernel.org
Subject: [PATCH] rust: devres: fix leaking call to devm_add_action()

When the data argument of Devres::new() is Err(), we leak the preceding
call to devm_add_action().

In order to fix this, call devm_add_action() in a unit type initializer in
try_pin_init!() after the initializers of all other fields.

Cc: stable@...r.kernel.org
Fixes: f5d3ef25d238 ("rust: devres: get rid of Devres' inner Arc")
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/devres.rs | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index da18091143a6..bfccf4177644 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -119,6 +119,7 @@ pub struct Devres<T: Send> {
     // impls can be removed.
     #[pin]
     inner: Opaque<Inner<T>>,
+    _add_action: (),
 }
 
 impl<T: Send> Devres<T> {
@@ -140,7 +141,15 @@ pub fn new<'a, E>(
             dev: dev.into(),
             callback,
             // INVARIANT: `inner` is properly initialized.
-            inner <- {
+            inner <- Opaque::pin_init(try_pin_init!(Inner {
+                    devm <- Completion::new(),
+                    revoke <- Completion::new(),
+                    data <- Revocable::new(data),
+            })),
+            // TODO: Replace with "initializer code blocks" [1] once available.
+            //
+            // [1] https://github.com/Rust-for-Linux/pin-init/pull/69
+            _add_action: {
                 // SAFETY: `this` is a valid pointer to uninitialized memory.
                 let inner = unsafe { &raw mut (*this.as_ptr()).inner };
 
@@ -153,12 +162,6 @@ pub fn new<'a, E>(
                 to_result(unsafe {
                     bindings::devm_add_action(dev.as_raw(), Some(callback), inner.cast())
                 })?;
-
-                Opaque::pin_init(try_pin_init!(Inner {
-                    devm <- Completion::new(),
-                    revoke <- Completion::new(),
-                    data <- Revocable::new(data),
-                }))
             },
         })
     }

base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
-- 
2.50.1