Commit 2ff33d66 authored Jan 08, 2019 by Jia-Ju Bai Committed by David S. Miller Jan 11, 2019

isdn: i4l: isdn_tty: Fix some concurrency double-free bugs



The functions isdn_tty_tiocmset() and isdn_tty_set_termios() may be
concurrently executed.

isdn_tty_tiocmset
  isdn_tty_modem_hup
    line 719: kfree(info->dtmf_state);
    line 721: kfree(info->silence_state);
    line 723: kfree(info->adpcms);
    line 725: kfree(info->adpcmr);

isdn_tty_set_termios
  isdn_tty_modem_hup
    line 719: kfree(info->dtmf_state);
    line 721: kfree(info->silence_state);
    line 723: kfree(info->adpcms);
    line 725: kfree(info->adpcmr);

Thus, some concurrency double-free bugs may occur.

These possible bugs are found by a static tool written by myself and
my manual code review.

To fix these possible bugs, the mutex lock "modem_info_mutex" used in
isdn_tty_tiocmset() is added in isdn_tty_set_termios().

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7fbe078c

drivers/isdn/i4l/isdn_tty.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -1437,15 +1437,19 @@ isdn_tty_set_termios(struct tty_struct tty, struct ktermios old_termios)
		{
		modem_info info = (modem_info ) tty->driver_data;

		mutex_lock(&modem_info_mutex);
		if (!old_termios)
		isdn_tty_change_speed(info);
		else {
		if (tty->termios.c_cflag == old_termios->c_cflag &&
		tty->termios.c_ispeed == old_termios->c_ispeed &&
		tty->termios.c_ospeed == old_termios->c_ospeed)
		tty->termios.c_ospeed == old_termios->c_ospeed) {
		mutex_unlock(&modem_info_mutex);
		return;
		}
		isdn_tty_change_speed(info);
		}
		mutex_unlock(&modem_info_mutex);
		}

		/*