linux-kernel - [PATCH AUTOSEL 4.19 033/101] serial: imx: fix locking in set

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Message-Id: <20190719040732.17285-33-sashal@kernel.org>
Date:   Fri, 19 Jul 2019 00:06:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sergey Organov <sorganov@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-serial@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 033/101] serial: imx: fix locking in set_termios()

From: Sergey Organov <sorganov@...il.com>

[ Upstream commit 4e828c3e09201512be5ee162393f334321f7cf01 ]

imx_uart_set_termios() called imx_uart_rts_active(), or
imx_uart_rts_inactive() before taking port->port.lock.

As a consequence, sport->port.mctrl that these functions modify
could have been changed without holding port->port.lock.

Moved locking of port->port.lock above the calls to fix the issue.

Signed-off-by: Sergey Organov <sorganov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/imx.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 0f67197a3783..105de92b0b3b 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -382,6 +382,7 @@ static void imx_uart_ucrs_restore(struct imx_port *sport,
 }
 #endif
 
+/* called with port.lock taken and irqs caller dependent */
 static void imx_uart_rts_active(struct imx_port *sport, u32 *ucr2)
 {
 	*ucr2 &= ~(UCR2_CTSC | UCR2_CTS);
@@ -390,6 +391,7 @@ static void imx_uart_rts_active(struct imx_port *sport, u32 *ucr2)
 	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
 }
 
+/* called with port.lock taken and irqs caller dependent */
 static void imx_uart_rts_inactive(struct imx_port *sport, u32 *ucr2)
 {
 	*ucr2 &= ~UCR2_CTSC;
@@ -399,6 +401,7 @@ static void imx_uart_rts_inactive(struct imx_port *sport, u32 *ucr2)
 	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
 }
 
+/* called with port.lock taken and irqs caller dependent */
 static void imx_uart_rts_auto(struct imx_port *sport, u32 *ucr2)
 {
 	*ucr2 |= UCR2_CTSC;
@@ -1554,6 +1557,16 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 		old_csize = CS8;
 	}
 
+	del_timer_sync(&sport->timer);
+
+	/*
+	 * Ask the core to calculate the divisor for us.
+	 */
+	baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16);
+	quot = uart_get_divisor(port, baud);
+
+	spin_lock_irqsave(&sport->port.lock, flags);
+
 	if ((termios->c_cflag & CSIZE) == CS8)
 		ucr2 = UCR2_WS | UCR2_SRST | UCR2_IRTS;
 	else
@@ -1597,16 +1610,6 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 			ucr2 |= UCR2_PROE;
 	}
 
-	del_timer_sync(&sport->timer);
-
-	/*
-	 * Ask the core to calculate the divisor for us.
-	 */
-	baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16);
-	quot = uart_get_divisor(port, baud);
-
-	spin_lock_irqsave(&sport->port.lock, flags);
-
 	sport->port.read_status_mask = 0;
 	if (termios->c_iflag & INPCK)
 		sport->port.read_status_mask |= (URXD_FRMERR | URXD_PRERR);
-- 
2.20.1