Hi Shuah, > tty_set_termios() has the following WARN_ON which can be triggered with a > syscall to invoke TIOCSETD __NR_ioctl. > > WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY && > tty->driver->subtype == PTY_TYPE_MASTER); > Reference: > https://syzkaller.appspot.com/bug?id=2410d22f1d8e5984217329dd0884b01d99e3e48d > > "The problem started with commit 7721383f4199 ("Bluetooth: hci_uart: Support > operational speed during setup") which introduced a new way for how > tty_set_termios() could end up being called for a master pty." > > Fix it by by preventing setting the HCI line discipline for PTYs in > hci_uart_tty_open(). > > Reported-by: syzbot+a950165cbb86bdd02...@syzkaller.appspotmail.com > Cc: Johan Hovold <jo...@kernel.org> > Cc: Marcel Holtmann <mar...@holtmann.org> > Cc: Al Viro <v...@zeniv.linux.org.uk> > Signed-off-by: Shuah Khan <sh...@kernel.org> > --- > drivers/bluetooth/hci_ldisc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c > index fbf7b4df23ab..c8faa4759cb7 100644 > --- a/drivers/bluetooth/hci_ldisc.c > +++ b/drivers/bluetooth/hci_ldisc.c > @@ -475,9 +475,9 @@ static int hci_uart_tty_open(struct tty_struct *tty) > BT_DBG("tty %p", tty); > > /* Error if the tty has no write op instead of leaving an exploitable > - * hole > + * hole. In addition check if setting HCI line discipline is allowed. > */
this comment is wrong. The result of setting the HCI line discipline is a call into hci_uart_tty_open. You have to check ops->write and ops->set_termios since both are required. That is it. > - if (tty->ops->write == NULL) > + if (tty->ops->write == NULL || tty->ops->set_termios == NULL) > return -EOPNOTSUPP; And while at it, change this to (!tty->ops->write). Regards Marcel
