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[34.125.53.210]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c7976fa40b2sm23658373a12.13.2026.04.27.09.39.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Apr 2026 09:39:59 -0700 (PDT) Date: Mon, 27 Apr 2026 16:39:55 +0000 From: Carlos Llamas To: Matthew Maurer Cc: Greg Kroah-Hartman , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Christian Brauner , Alice Ryhl , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , Wedson Almeida Filho , Matt Gilbride , Paul Moore , stable@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, David Stevens Subject: Re: [PATCH] rust_binder: Avoid holding lock when dropping delivered_death Message-ID: References: <20260403-lockhold-v1-1-c332b56cd8ae@google.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 > Signed-off-by: Matthew Maurer > Cc: stable@vger.kernel.org > Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver") > --- Acked-by: Carlos Llamas