From: Carlos Llamas <cmllamas@google.com>
To: Matthew Maurer <mmaurer@google.com>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Todd Kjos" <tkjos@android.com>,
"Christian Brauner" <brauner@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Boqun Feng" <boqun@kernel.org>, "Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Matt Gilbride" <mattgilbride@google.com>,
"Paul Moore" <paul@paul-moore.com>,
stable@vger.kernel.org, linux-kernel@vger.kernel.org,
rust-for-linux@vger.kernel.org,
"David Stevens" <stevensd@google.com>
Subject: Re: [PATCH] rust_binder: Avoid holding lock when dropping delivered_death
Date: Mon, 27 Apr 2026 16:39:55 +0000 [thread overview]
Message-ID: <ae-RW3Pdw7-sN-Dt@google.com> (raw)
In-Reply-To: <20260403-lockhold-v1-1-c332b56cd8ae@google.com>
On Fri, Apr 03, 2026 at 06:18:58PM +0000, Matthew Maurer wrote:
> In 6c37bebd8c926, we switched to looping over the list and dropping each
> individual node, ostensibly without the lock held in the loop body.
>
> If the kernel were using Rust Edition 2024, the comment would be
> accurate, and the lock would not be held across the drop. However, the
> kernel is currently using 2021, so tail expression lifetime extension
> results in the lock being held across the drop. Explicitly binding the
> expression result to a variable makes the lockguard no longer part of a
> tail expression, causing the lock to be dropped before entering the loop
> body.
>
> This was detected via `CONFIG_PROVE_LOCKING` identifying an invalid wait
> context at the drop site.
>
> Reported-by: David Stevens <stevensd@google.com>
> Signed-off-by: Matthew Maurer <mmaurer@google.com>
> Cc: stable@vger.kernel.org
> Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
> ---
Acked-by: Carlos Llamas <cmllamas@google.com>
next prev parent reply other threads:[~2026-04-27 16:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-03 18:18 [PATCH] rust_binder: Avoid holding lock when dropping delivered_death Matthew Maurer
2026-04-04 8:10 ` Alice Ryhl
2026-04-27 16:39 ` Carlos Llamas [this message]
2026-04-28 7:24 ` Alice Ryhl
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