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SubjectRe: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()
On Wed, Jan 30, 2019 at 11:07:38AM +0100, Johan Hovold wrote:
> On Sun, Jan 27, 2019 at 10:53:02PM -0800, Myungho Jung wrote:
> > tty_set_termios() should be called with slave side of pty driver. So, If
> > tty driver is pty master, it needs to be switched to ->link.
>
> I'm not sure that's the right solution. PTYs are virtual devices used
> for IPC and neither end (master or slave) have support for modem
> control or baud rates.
>
> > Reported-by: syzbot+a950165cbb86bdd023a4@syzkaller.appspotmail.com
> > Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> > ---
> > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> > 1 file changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> > index fbf7b4df23ab..90c5ea8c399b 100644
> > --- a/drivers/bluetooth/hci_ldisc.c
> > +++ b/drivers/bluetooth/hci_ldisc.c
> > @@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> > return 0;
> > }
> >
> > +/* If driver is pty master, return slave side */
> > +static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
> > +{
> > + return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> > + tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
> > +}
> > +
> > /* Flow control or un-flow control the device */
> > void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > {
> > struct tty_struct *tty = hu->tty;
> > + struct tty_struct *real_tty;
> > struct ktermios ktermios;
> > int status;
> > unsigned int set = 0;
> > @@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > return;
> > }
> >
> > + real_tty = hci_uart_get_real_tty(tty);
> > if (enable) {
> > /* Disable hardware flow control */
> > - ktermios = tty->termios;
> > + ktermios = real_tty->termios;
> > ktermios.c_cflag &= ~CRTSCTS;
> > - status = tty_set_termios(tty, &ktermios);
> > + status = tty_set_termios(real_tty, &ktermios);
> > BT_DBG("Disabling hardware flow control: %s",
> > status ? "failed" : "success");
>
> So instead of these pointless calls to set the slave termios and
> modem-control state, you might as well bail out early above (and
> similarly in set_baudrate()).
>
> Using n_hci for a master pty really makes no sense at all, so we could
> even bail out at ldisc open, but perhaps that can be discussed and
> addressed later.
>
> Johan

Hi Johan,

I fixed it to just return -EOPNOTSUPP if NULL in ath_setup().

Thanks,
Myungho

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