linux-kernel - [PATCH AUTOSEL for 3.18 2/8] serial: 8250_fintek: Fix rs485 disablement on invalid ioctl()

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Message-ID: <20171122222653.20265-2-alexander.levin@verizon.com>
Date:   Wed, 22 Nov 2017 22:26:58 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Lukas Wunner <lukas@...ner.de>,
        Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 3.18 2/8] serial: 8250_fintek: Fix rs485
 disablement on invalid ioctl()

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>
---
 drivers/tty/serial/8250/8250_fintek.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_fintek.c b/drivers/tty/serial/8250/8250_fintek.c
index 1bb28cb69493..c72283f2be6d 100644
--- a/drivers/tty/serial/8250/8250_fintek.c
+++ b/drivers/tty/serial/8250/8250_fintek.c
@@ -118,7 +118,7 @@ static int fintek_8250_rs4850_config(struct uart_8250_port *uart,
 
 	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;
 
-- 
2.11.0