[PATCH 1/4] tty: Drop tty->count on tty_reopen() failure

From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: "Dmitry Safonov" <0x7f454c46@gmail.com>,
	"Dmitry Safonov" <dima@arista.com>,
	"Daniel Axtens" <dja@axtens.net>,
	"Dmitry Vyukov" <dvyukov@google.com>,
	"Michael Neuling" <mikey@neuling.org>,
	"Mikulas Patocka" <mpatocka@redhat.com>,
	"Pasi Kärkkäinen" <pasik@iki.fi>,
	"Peter Hurley" <peter@hurleysoftware.com>,
	"Sergey Senozhatsky" <sergey.senozhatsky.work@gmail.com>,
	"Tan Xiaojun" <tanxiaojun@huawei.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Jiri Slaby" <jslaby@suse.com>,
	stable@vger.kernel.org
Subject: [PATCH 1/4] tty: Drop tty->count on tty_reopen() failure
Date: Wed, 29 Aug 2018 03:23:50 +0100	[thread overview]
Message-ID: <20180829022353.23568-2-dima@arista.com> (raw)
In-Reply-To: <20180829022353.23568-1-dima@arista.com>

In case of tty_ldisc_reinit() failure, tty->count should be decremented
back, otherwise we will never release_tty().
Never seen it in the real life, but it seems not really hard to hit.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 drivers/tty/tty_io.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 32bc3e3fe4d3..5e5da9acaf0a 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1255,6 +1255,7 @@ static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *
 static int tty_reopen(struct tty_struct *tty)
 {
 	struct tty_driver *driver = tty->driver;
+	int retval;
 
 	if (driver->type == TTY_DRIVER_TYPE_PTY &&
 	    driver->subtype == PTY_TYPE_MASTER)
@@ -1268,10 +1269,14 @@ static int tty_reopen(struct tty_struct *tty)
 
 	tty->count++;
 
-	if (!tty->ldisc)
-		return tty_ldisc_reinit(tty, tty->termios.c_line);
+	if (tty->ldisc)
+		return 0;
 
-	return 0;
+	retval = tty_ldisc_reinit(tty, tty->termios.c_line);
+	if (retval)
+		tty->count--;
+
+	return retval;
 }
 
 /**
-- 
2.13.6

