From 90dbad8cd6efccbdce109d5ef0724f8434a6cdde Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Fri, 3 Nov 2017 15:30:56 +0100
Subject: [PATCH] serdev: ttyport: fix tty locking in close
Git-commit: 90dbad8cd6efccbdce109d5ef0724f8434a6cdde
Patch-mainline: v4.15-rc3
References: bsc#1051510

Make sure to hold the tty lock as required when calling tty-driver
close() (e.g. to avoid racing with hangup()).

Note that the serport active flag is currently set under the lock at
controller open, but really isn't protected by it.

Fixes: cd6484e1830b ("serdev: Introduce new bus for serial attached devices")
Signed-off-by: Johan Hovold <johan@kernel.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/serdev/serdev-ttyport.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -162,8 +162,10 @@ static void ttyport_close(struct serdev_
 
 	clear_bit(SERPORT_ACTIVE, &serport->flags);
 
+	tty_lock(tty);
 	if (tty->ops->close)
 		tty->ops->close(tty, NULL);
+	tty_unlock(tty);
 
 	tty_release_struct(tty, serport->tty_idx);
 }