* [PATCH v4] bluetooth: Fix WARNING in tty_set_termios()
@ 2019-02-03 19:38 Shuah Khan
2019-02-04 5:39 ` Marcel Holtmann
0 siblings, 1 reply; 3+ messages in thread
From: Shuah Khan @ 2019-02-03 19:38 UTC (permalink / raw)
To: marcel, johan.hedberg, johan, viro
Cc: Shuah Khan, linux-bluetooth, linux-kernel
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.
*/
- if (tty->ops->write == NULL)
+ if (tty->ops->write == NULL || tty->ops->set_termios == NULL)
return -EOPNOTSUPP;
hu = kzalloc(sizeof(struct hci_uart), GFP_KERNEL);
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4] bluetooth: Fix WARNING in tty_set_termios()
2019-02-03 19:38 [PATCH v4] bluetooth: Fix WARNING in tty_set_termios() Shuah Khan
@ 2019-02-04 5:39 ` Marcel Holtmann
2019-02-04 18:44 ` shuah
0 siblings, 1 reply; 3+ messages in thread
From: Marcel Holtmann @ 2019-02-04 5:39 UTC (permalink / raw)
To: Shuah Khan
Cc: Johan Hedberg, Johan Hovold, Al Viro, Bluez mailing list, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v4] bluetooth: Fix WARNING in tty_set_termios()
2019-02-04 5:39 ` Marcel Holtmann
@ 2019-02-04 18:44 ` shuah
0 siblings, 0 replies; 3+ messages in thread
From: shuah @ 2019-02-04 18:44 UTC (permalink / raw)
To: Marcel Holtmann
Cc: Johan Hedberg, Johan Hovold, Al Viro, Bluez mailing list,
linux-kernel, shuah
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-02-03 19:38 [PATCH v4] bluetooth: Fix WARNING in tty_set_termios() Shuah Khan
2019-02-04 5:39 ` Marcel Holtmann
2019-02-04 18:44 ` shuah
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