tty: fix crash in release_tty if tty->port is not set

HiassofT · gregkh · commit 4466d6d2f80c · 2020-11-06T17:24:49.000+01:00
Commit 2ae0b31 ("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: 2ae0b31 ("tty: don't crash in tty_init_dev when missing tty_port") Signed-off-by: Matthias Reichl <hias@horus.com> Link: https://lore.kernel.org/r/20201105123432.4448-1-hias@horus.com Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git 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);
 
