On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
> 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@xxxxxxxxxx>
> Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
> ---
> 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 4eae1406cb6c..661074ab8edb 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1448,6 +1448,9 @@ 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;
> +
> uart_port_lock_irqsave(port, &flags);
> aux = port->rs485;
> uart_port_unlock_irqrestore(port, flags);
> @@ -1465,7 +1468,7 @@ 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)))
Looking through debian code search entries for TIOCGRS485, this might
actually fly... I'd suggest splitting this into two patches though.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
--
i.
