linux-kernel - [PATCH 5/8] serdev: ttyport: fix tty locking in close

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Date:   Fri,  3 Nov 2017 15:30:56 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH 5/8] serdev: ttyport: fix tty locking in close

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

diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
index 31c05665a0e6..334bce00364f 100644
--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -162,8 +162,10 @@ static void ttyport_close(struct serdev_controller *ctrl)
 
 	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);
 }
-- 
2.15.0