linux-kernel - [PATCH -next 2/5] serial: core: Claim port mutex for set

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Date:	Wed,  5 Nov 2014 13:11:42 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH -next 2/5] serial: core: Claim port mutex for set_ldisc()

Three UART drivers (8250, atmel & amba-pl010) enable modem status
interrupts if the line discipline is changed to N_PPS. However,
the uart port flags may only be safely modified while holding the
port mutex.

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
 drivers/tty/serial/serial_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 1a2d90f..5209eaa 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1245,8 +1245,11 @@ static void uart_set_ldisc(struct tty_struct *tty)
 	struct uart_state *state = tty->driver_data;
 	struct uart_port *uport = state->uart_port;
 
-	if (uport->ops->set_ldisc)
+	if (uport->ops->set_ldisc) {
+		mutex_lock(&state->port.mutex);
 		uport->ops->set_ldisc(uport, tty->termios.c_line);
+		mutex_unlock(&state->port.mutex);
+	}
 }
 
 static void uart_set_termios(struct tty_struct *tty,
-- 
2.1.3

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