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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Q34KGzie; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C833E606A31B; Tue, 27 Oct 2026 11:16:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Q34KGzie Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C2531F01825; Tue, 27 Oct 2026 11:16:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793099806; bh=yPv5p+sEloJUUYC5PLdURybRSNu6Ze9OVlX0ezUUl50=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Q34KGzieN3gXoPvF6uFxKWHy3Rqtt0zM5tqC76zFvVrpcw1e1+ACrGKcGge/82+q4 Ll/UWqhui6ecfIBOrzSgW6nE53b4F5Cbn57R8HbVfx3mOmnFpHYbtjO8zxb1TesHEj 8EhHkYGvD0wZhObzmYwiDK4ybyfiULiTW7n3Mn3QRJuXUu7k7jLcTDA/VM157287JP MoPg6nqQuIXL69fAsWq6402V7BnMUcON7knWfqkMgFxUZbWoXccqftfZP/X8pYZYHy X8u3sEgvflkyg+ZavKdfPM4t6V6LyC71QMhsM9KsQ2dg80yp8dpTXTw6mDSDs6Nbk1 ctB1tiCfhh09A== Message-ID: <46833c7c-9c49-403e-bdb6-e9cf5fc2d3aa@kernel.org> Date: Tue, 27 Oct 2026 12:16:37 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 05/24] serial: 8250: clear subdriver state on port unregister To: Greg Kroah-Hartman , Joshua Rogers , Chris Mason , Josef Bacik Cc: Tony Lindgren , Rafael Gago Castano , Florian Fainelli , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , Andy Shevchenko , Peter Hurley , Heikki Krogerus , Crescent Hsieh , Frank Li , Sherry Sun , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Manivannan Sadhasivam , Olof Johansson , =?UTF-8?Q?Andreas_F=C3=A4rber?= , Arnd Bergmann , Krzysztof Kozlowski , Peter Griffin , Alim Akhtar , Robert Baldyga , Thomas Abraham , Kukjin Kim , Patrice Chotard , Srinivas Kandagatla , Maxime Coquelin , Alexandre Torgue , Andy Shevchenko , Vladimir Zapolskiy , Al Cooper , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, stable , John Ogness , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig_=28The_Capable_Hub=29?= , Fushuai Wang References: <20261027-tty-llm-v1-0-99b0202ae546@linuxfoundation.org> <20261027-tty-llm-v1-5-99b0202ae546@linuxfoundation.org> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 27. 10. 26, 12:06, Greg Kroah-Hartman wrote: > From: Joshua Rogers > > When serial8250_unregister_port() re-adds a port as a fallback ISA port, > it only partially resets the port state via serial8250_init_port(). All > subdriver-owned function pointers and per-driver state copied during > registration (such as startup, shutdown, handle_break, get_mctrl, > set_mctrl, set_termios, private_data, dma, gpios, and rs485 callbacks) > are left intact. After the original driver module is unloaded, these > become dangling pointers that can trigger use-after-free on subsequent > port operations. > > Clear all subdriver-copied fields and call serial8250_set_defaults() to > restore default I/O accessors before re-adding the fallback port. > > Cc: stable > Cc: Jiri Slaby > Cc: John Ogness > Cc: Crescent Hsieh > Cc: "Uwe Kleine-König (The Capable Hub)" > Cc: Fushuai Wang > Signed-off-by: Joshua Rogers > Signed-off-by: Greg Kroah-Hartman > --- > drivers/tty/serial/8250/8250_core.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > index 0951d3e42e1f..673fde55828a 100644 > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -956,7 +956,35 @@ void serial8250_unregister_port(struct uart_8250_port *uart) > uart->port.dev = &serial8250_isa_devs->dev; > uart->port.port_id = uart->port.line; > uart->capabilities = 0; > + > + /* > + * Clear subdriver-owned state copied by > + * serial8250_register_8250_port() to prevent dangling > + * pointers after the original driver module is unloaded. > + */ > + uart->port.private_data = NULL; > + uart->port.set_termios = NULL; > + uart->port.set_ldisc = NULL; > + uart->port.get_mctrl = NULL; > + uart->port.set_mctrl = NULL; > + uart->port.get_divisor = NULL; > + uart->port.set_divisor = NULL; > + uart->port.startup = NULL; > + uart->port.shutdown = NULL; > + uart->port.throttle = NULL; > + uart->port.unthrottle = NULL; > + uart->port.handle_break = NULL; > + uart->port.rs485_config = NULL; > + memset(&uart->port.rs485, 0, sizeof(uart->port.rs485)); > + memset(&uart->port.rs485_supported, 0, > + sizeof(uart->port.rs485_supported)); > + uart->gpios = NULL; > + uart->dma = NULL; > + uart->rs485_start_tx = NULL; > + uart->rs485_stop_tx = NULL; > + Ha! The above gives an answer to my today's: https://lore.kernel.org/all/53624662-e94e-4fcb-9902-7fa4143c7689@kernel.org/ (And obviously this conflicts with that patch.) And with the current state of LLMs, I should perhaps revive my "move ops to a separate struct" as the above is a PITA. I have been unable to finish the series on my own to date. > serial8250_init_port(uart); > + serial8250_set_defaults(uart); > serial8250_apply_quirks(uart); > uart_add_one_port(&serial8250_reg, &uart->port); > } else { > thanks, -- js suse labs