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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>
This commit is contained in:
Jia-Ju Bai 2019-01-08 21:04:48 +08:00 committed by David S. Miller
parent 7fbe078c37
commit 2ff33d6637
1 changed files with 5 additions and 1 deletions
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6
drivers/isdn/i4l/isdn_tty.c
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@ -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);
}
/*