linux-kernel - [PATCH] tty: fix crash in release

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Message-Id: <20201105123432.4448-1-hias@horus.com>
Date:   Thu,  5 Nov 2020 13:34:32 +0100
From:   Matthias Reichl <hias@...us.com>
To:     Jiri Slaby <jirislaby@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Samuel Thibault <samuel.thibault@...-lyon.org>,
        linux-kernel@...r.kernel.org, Matthias Reichl <hias@...us.com>
Subject: [PATCH] tty: fix crash in release_tty if tty->port is not set

Commit 2ae0b31e0face ("tty: don't crash in tty_init_dev when missing
tty_port") didn't fully prevent the crash as the cleanup path in
tty_init_dev() calls release_tty() which dereferences tty->port
without checking it for non-null.

Add tty->port checks to release_tty to avoid the kernel crash.

Fixes: 2ae0b31e0face ("tty: don't crash in tty_init_dev when missing tty_port")
Signed-off-by: Matthias Reichl <hias@...us.com>
---
 drivers/tty/tty_io.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 7a4c02548fb3f..9f8b9a567b359 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1515,10 +1515,12 @@ static void release_tty(struct tty_struct *tty, int idx)
 		tty->ops->shutdown(tty);
 	tty_save_termios(tty);
 	tty_driver_remove_tty(tty->driver, tty);
-	tty->port->itty = NULL;
+	if (tty->port)
+		tty->port->itty = NULL;
 	if (tty->link)
 		tty->link->port->itty = NULL;
-	tty_buffer_cancel_work(tty->port);
+	if (tty->port)
+		tty_buffer_cancel_work(tty->port);
 	if (tty->link)
 		tty_buffer_cancel_work(tty->link->port);
 
-- 
2.20.1