linux-kernel - [PATCH 1/2] tty: serial_core: Fix serial console crash on port shutdown

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Date:   Fri, 28 Oct 2016 07:07:47 -0500
From:   Rob Herring <robh@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Mike Galbraith <mgalbraith@...e.de>,
        Jiri Slaby <jslaby@...e.cz>, linux-serial@...r.kernel.org,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Mugunthan V N <mugunthanvnm@...com>
Subject: [PATCH 1/2] tty: serial_core: Fix serial console crash on port shutdown

From: Geert Uytterhoeven <geert+renesas@...der.be>

The port->console flag is always false, as uart_console() is called
before the serial console has been registered.

Hence for a serial port used as the console, uart_tty_port_shutdown()
will still be called when userspace closes the port, powering it down.
This may lead to a system lock up when the serial console driver writes
to the serial port's registers.

To fix this, move the setting of port->console after the call to
uart_configure_port(), which registers the serial console.

Fixes: 761ed4a94582ab29 ("tty: serial_core: convert uart_close to use tty_port_close")
Reported-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Acked-by: Rob Herring <robh@...nel.org>
Tested-by: Mugunthan V N <mugunthanvnm@...com>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
[robh: rebased on tty-linus]
Signed-off-by: Rob Herring <robh@...nel.org>
---
 drivers/tty/serial/serial_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 664c99aeeca5..ce8899c13af3 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2759,6 +2759,8 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 
 	uart_configure_port(drv, state, uport);
 
+	port->console = uart_console(uport);
+
 	num_groups = 2;
 	if (uport->attr_group)
 		num_groups++;
-- 
2.10.1