linux-kernel - [PATCH AUTOSEL 4.14 15/25] serial: msm_serial: disable interrupts in __msm_console

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Message-Id: <20220607180229.482040-15-sashal@kernel.org>
Date:   Tue,  7 Jun 2022 14:02:16 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     John Ogness <john.ogness@...utronix.de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Petr Mladek <pmladek@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, agross@...nel.org,
        bjorn.andersson@...aro.org, jirislaby@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 15/25] serial: msm_serial: disable interrupts in __msm_console_write()

From: John Ogness <john.ogness@...utronix.de>

[ Upstream commit aabdbb1b7a5819e18c403334a31fb0cc2c06ad41 ]

__msm_console_write() assumes that interrupts are disabled, but
with threaded console printers it is possible that the write()
callback of the console is called with interrupts enabled.

Explicitly disable interrupts using local_irq_save() to preserve
the assumed context.

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: John Ogness <john.ogness@...utronix.de>
Link: https://lore.kernel.org/r/20220506213324.470461-1-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/msm_serial.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 7848e9455950..3df3716caa56 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -1587,6 +1587,7 @@ static inline struct uart_port *msm_get_port_from_line(unsigned int line)
 static void __msm_console_write(struct uart_port *port, const char *s,
 				unsigned int count, bool is_uartdm)
 {
+	unsigned long flags;
 	int i;
 	int num_newlines = 0;
 	bool replaced = false;
@@ -1604,6 +1605,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,
 			num_newlines++;
 	count += num_newlines;
 
+	local_irq_save(flags);
+
 	if (port->sysrq)
 		locked = 0;
 	else if (oops_in_progress)
@@ -1649,6 +1652,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,
 
 	if (locked)
 		spin_unlock(&port->lock);
+
+	local_irq_restore(flags);
 }
 
 static void msm_console_write(struct console *co, const char *s,
-- 
2.35.1