4.9-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 2ff33d6637393fe9348357285931811b76e1402f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 63eaa0a9f8a18..d4e0d1602c80f 100644 --- a/drivers/isdn/i4l/isdn_tty.c +++ b/drivers/isdn/i4l/isdn_tty.c @@ -1455,15 +1455,19 @@ 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); }
/*