From 9a965fba11f356fca64c86b11fa7d421ccdb1e5f Mon Sep 17 00:00:00 2001 From: Lino Sanfilippo Date: Wed, 3 Jan 2024 07:18:15 +0100 Subject: [PATCH] serial: core: make sure RS485 cannot be enabled when it is not supported MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit c73986913fa47e71e0b1ad7f039f6444915e8810 upstream. 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 Cc: Sascha Hauer Cc: Reviewed-by: Ilpo Järvinen Signed-off-by: Lino Sanfilippo Link: https://lore.kernel.org/r/20240103061818.564-5-l.sanfilippo@kunbus.com Signed-off-by: Greg Kroah-Hartman --- 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 e56d34d..50e1b26 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1453,7 +1453,7 @@ 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))) -- 2.7.4