This is a note to let you know that I've just added the patch titled

serial: core: make sure RS485 cannot be enabled when it is not

to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From c73986913fa47e71e0b1ad7f039f6444915e8810 Mon Sep 17 00:00:00 2001 From: Lino Sanfilippo l.sanfilippo@kunbus.com Date: Wed, 3 Jan 2024 07:18:15 +0100 Subject: serial: core: make sure RS485 cannot be enabled when it is not supported MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

Some uart drivers specify a rs485_config() function and then decide later to disable RS485 support for some reason (e.g. imx and ar933).

In these cases userspace may be able to activate RS485 via TIOCSRS485 nevertheless, since in uart_set_rs485_config() an existing rs485_config() function indicates that RS485 is supported.

Make sure that this is not longer possible by checking the uarts rs485_supported.flags instead and bailing out if SER_RS485_ENABLED is not set.

Furthermore instead of returning an empty structure return -ENOTTY if the RS485 configuration is requested via TIOCGRS485 but RS485 is not supported. This has a small impact on userspace visibility but it is consistent with the -ENOTTY error for TIOCGRS485.

Fixes: e849145e1fdd ("serial: ar933x: Fill in rs485_supported") Fixes: 55e18c6b6d42 ("serial: imx: Remove serial_rs485 sanitization") Cc: Shawn Guo shawnguo@kernel.org Cc: Sascha Hauer s.hauer@pengutronix.de Cc: stable@vger.kernel.org Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com Link: https://lore.kernel.org/r/20240103061818.564-5-l.sanfilippo@kunbus.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/serial_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index cd8c3a70455e..b9606db78c92 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1474,7 +1474,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port, int ret; unsigned long flags;

- if (!port->rs485_config) + if (!(port->rs485_supported.flags & SER_RS485_ENABLED)) return -ENOTTY;

if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))