Re: [PATCH v2] tty: Fix WARNING in tty_set_termios()

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jan 31, 2019 at 04:23:59PM -0700, Shuah Khan wrote:
> 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@syzkaller.appspotmail.com
> Signed-off-by: Shuah Khan <shuah@kernel.org>
> ---
>  drivers/bluetooth/hci_ldisc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)

I think the subject should be something like:
	"bluetooth: hci: Fix warning in tty_set_termios()"
it isn't a tty core problem :)

thanks,

greg k-h