Commit 4afeced5 authored Jan 03, 2024 by Lino Sanfilippo Committed by Greg Kroah-Hartman Jan 04, 2024

serial: core: fix sanitizing check for RTS settings



Among other things uart_sanitize_serial_rs485() tests the sanity of the RTS
settings in a RS485 configuration that has been passed by userspace.
If RTS-on-send and RTS-after-send are both set or unset the configuration
is adjusted and RTS-after-send is disabled and RTS-on-send enabled.

This however makes only sense if both RTS modes are actually supported by
the driver.

With commit be2e2cb1 ("serial: Sanitize rs485_struct") the code does
take the driver support into account but only checks if one of both RTS
modes are supported. This may lead to the errorneous result of RTS-on-send
being set even if only RTS-after-send is supported.

Fix this by changing the implemented logic: First clear all unsupported
flags in the RS485 configuration, then adjust an invalid RTS setting by
taking into account which RTS mode is supported.

Cc:  <stable@vger.kernel.org>
Fixes: be2e2cb1 ("serial: Sanitize rs485_struct")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240103061818.564-4-l.sanfilippo@kunbus.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 1a33e33c

drivers/tty/serial/serial_core.c

+18 −10

Original line number	Diff line number	Diff line
		@@ -1376,19 +1376,27 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
		return;
		}

		rs485->flags &= supported_flags;

		/* Pick sane settings if the user hasn't */
		if ((supported_flags & (SER_RS485_RTS_ON_SEND\|SER_RS485_RTS_AFTER_SEND)) &&
		!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
		if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
		!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
		if (supported_flags & SER_RS485_RTS_ON_SEND) {
		rs485->flags \|= SER_RS485_RTS_ON_SEND;
		rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;

		dev_warn_ratelimited(port->dev,
		"%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
		port->name, port->line);
		rs485->flags \|= SER_RS485_RTS_ON_SEND;
		rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
		supported_flags \|= SER_RS485_RTS_ON_SEND\|SER_RS485_RTS_AFTER_SEND;
		}
		} else {
		rs485->flags \|= SER_RS485_RTS_AFTER_SEND;
		rs485->flags &= ~SER_RS485_RTS_ON_SEND;

		rs485->flags &= supported_flags;
		dev_warn_ratelimited(port->dev,
		"%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
		port->name, port->line);
		}
		}

		uart_sanitize_serial_rs485_delays(port, rs485);