linux-kernel - Re: [PATCH 5/6] serial: core: make sure RS485 is cannot be enabled when it is not supported

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Message-Id: <20230929081712.7824dca40828ff873b3352ff@hugovil.com>
Date:   Fri, 29 Sep 2023 08:17:12 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de,
        ilpo.jarvinen@...ux.intel.com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, l.sanfilippo@...bus.com,
        lukas@...ner.de, p.rosenberger@...bus.com, stable@...r.kernel.org
Subject: Re: [PATCH 5/6] serial: core: make sure RS485 is cannot be enabled
 when it is not supported

Hi,
remove superfluous "is" after RS485 in patch title.

Hugo.



On Fri, 29 Sep 2023 00:12:45 +0200
Lino Sanfilippo <LinoSanfilippo@....de> wrote:

> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> 
> 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.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
> ---
>  drivers/tty/serial/serial_core.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index f4feebf8200f..dca09877fabc 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1432,6 +1432,9 @@ static int uart_get_rs485_config(struct uart_port *port,
>  	unsigned long flags;
>  	struct serial_rs485 aux;
>  
> +	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
> +		return -ENOTTY;
> +
>  	spin_lock_irqsave(&port->lock, flags);
>  	aux = port->rs485;
>  	spin_unlock_irqrestore(&port->lock, flags);
> @@ -1449,7 +1452,7 @@ 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)))
> -- 
> 2.40.1
>