2019-01-08 13:37:26

by Jia-Ju Bai

Subject: [PATCH] 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 <[email protected]>
---
drivers/isdn/i4l/isdn_tty.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/isdn/i4l/isdn_tty.c b/drivers/isdn/i4l/isdn_tty.c
index 1b2239c1d569..dc1cded716c1 100644
--- a/drivers/isdn/i4l/isdn_tty.c
+++ b/drivers/isdn/i4l/isdn_tty.c
@@ -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);
}

/*
--
2.17.0

2019-01-12 01:59:29

by David Miller

Subject: Re: [PATCH] isdn: i4l: isdn_tty: Fix some concurrency double-free bugs

From: Jia-Ju Bai <[email protected]>
Date: Tue, 8 Jan 2019 21:04:48 +0800

> The functions isdn_tty_tiocmset() and isdn_tty_set_termios() may be
> concurrently executed.
...
> 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 <[email protected]>

Applied.