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 the problem by preventing setting the HCI line discipline for PTYs > from hci_uart_setup() and hci_uart_set_flow_control(). > > The reproducer is used to reproduce the problem and verify the fix. > > Reported-by: syzbot+a950165cbb86bdd023a4@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Shuah Khan <shuah@xxxxxxxxxx> > --- > drivers/bluetooth/hci_ldisc.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c > index fbf7b4df23ab..ce84ca91ca70 100644 > --- a/drivers/bluetooth/hci_ldisc.c > +++ b/drivers/bluetooth/hci_ldisc.c > @@ -314,6 +314,11 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable) > return; > } > > + /* don't set HCI line discipline on PTYs */ > + if (tty->driver->type == TTY_DRIVER_TYPE_PTY && > + tty->driver->subtype == PTY_TYPE_MASTER) > + return; > + just do it once in hci_uart_tty_open. Actually we already check for ops->write and so lets just ensure all ops we ever call are present. If they are not, then bail out. I wouldn’t even bother with the TTY type. Wouldn’t that be a lot simpler? Regards Marcel
