linux-kernel - Re: [PATCH v2] rust: devres: fix leaking call to devm_add

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Message-ID: <aJw7sx0p0Ec-oLkz@google.com>
Date: Wed, 13 Aug 2025 07:16:03 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: 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, 
	tmgross@...ch.edu, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rust: devres: fix leaking call to devm_add_action()

On Tue, Aug 12, 2025 at 03:09:06PM +0200, Danilo Krummrich wrote:
> 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.
> 
> Fixes: f5d3ef25d238 ("rust: devres: get rid of Devres' inner Arc")
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>

This looks ok:

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>

But can't we do it like this instead?
1. Allocate devm job.
2. Initialize inner field.
3. Use allocation from (1.) to devm_add_action() infallibly.

This way, there's no risk that the inner value may get dropped, which
could be an expensive operation.

Alice