From: Marcel Holtmann <marcel@holtmann.org>
To: Shuah Khan <shuah@kernel.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>,
Johan Hovold <johan@kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Bluez mailing list <linux-bluetooth@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] bluetooth: Fix WARNING in tty_set_termios()
Date: Mon, 4 Feb 2019 06:39:36 +0100 [thread overview]
Message-ID: <EBD36B7C-0B26-4483-B7C8-736F27B9D267@holtmann.org> (raw)
In-Reply-To: <20190203193848.12959-1-shuah@kernel.org>
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.
> - 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
next prev parent reply other threads:[~2019-02-04 5:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-03 19:38 [PATCH v4] bluetooth: Fix WARNING in tty_set_termios() Shuah Khan
2019-02-04 5:39 ` Marcel Holtmann [this message]
2019-02-04 18:44 ` shuah
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