Messages in this thread | | | Subject | Re: [PATCH v4] bluetooth: Fix WARNING in tty_set_termios() | From | shuah <> | Date | Mon, 4 Feb 2019 11:44:36 -0700 |
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On 2/3/19 10:39 PM, Marcel Holtmann wrote: > 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+a950165cbb86bdd023a4@syzkaller.appspotmail.com >> Cc: Johan Hovold <johan@kernel.org> >> Cc: Marcel Holtmann <marcel@holtmann.org> >> Cc: Al Viro <viro@zeniv.linux.org.uk> >> Signed-off-by: Shuah Khan <shuah@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.
I will fix the comment.
> >> - 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). >
Okay. I will fix both.
thanks, -- Shuah
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