linux-kernel - [PATCH 4.9 017/109] serial: 8250_fintek: Fix rs485 disablement on invalid ioctl()

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Message-Id: <20171207125636.656322166@linuxfoundation.org>
Date:   Thu,  7 Dec 2017 13:56:01 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 017/109] serial: 8250_fintek: Fix rs485 disablement on invalid ioctl()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukas Wunner <lukas@...ner.de>


[ Upstream commit 3236a965486ba0c6043cf2c7b51943d8b382ae29 ]

This driver's ->rs485_config callback checks if SER_RS485_RTS_ON_SEND
and SER_RS485_RTS_AFTER_SEND have the same value.  If they do, it means
the user has passed in invalid data with the TIOCSRS485 ioctl()
since RTS must have a different polarity when sending and when not
sending.  In this case, rs485 mode is not enabled (the RS485_URA bit
is not set in the RS485 Enable Register) and this is supposed to be
signaled back to the user by clearing the SER_RS485_ENABLED bit in
struct serial_rs485 ... except a missing tilde character is preventing
that from happening.

Fixes: 28e3fb6c4dce ("serial: Add support for Fintek F81216A LPC to 4 UART")
Cc: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc: "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>
Signed-off-by: Lukas Wunner <lukas@...ner.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/tty/serial/8250/8250_fintek.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/tty/serial/8250/8250_fintek.c
+++ b/drivers/tty/serial/8250/8250_fintek.c
@@ -121,7 +121,7 @@ static int fintek_8250_rs485_config(stru
 
 	if ((!!(rs485->flags & SER_RS485_RTS_ON_SEND)) ==
 			(!!(rs485->flags & SER_RS485_RTS_AFTER_SEND)))
-		rs485->flags &= SER_RS485_ENABLED;
+		rs485->flags &= ~SER_RS485_ENABLED;
 	else
 		config |= RS485_URA;