[PATCH v2] Bluetooth: hci_ldisc: check for missing tty operations

[PATCH v2] Bluetooth: hci_ldisc: check for missing tty operations

[Vladis Dronov]

Certain ttys operations (pty_unix98_ops) lack tiocmget() and tiocmset()
functions which are called by the certain HCI UART protocols (hci_ath,
hci_bcm, hci_intel, hci_mrvl, hci_qca) via hci_uart_set_flow_control()
or directly. This leads to an execution at NULL and can be triggered by
an unprivileged user. Fix this by adding a check for the missing tty
operations the same way it is done for write().

This fixes CVE-2019-10207. The Fixes: lines list commits where calls to
tiocm[gs]et() or hci_uart_set_flow_control() were added to the HCI UART
protocols.

Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
Reported-by: syzbot+79337b501d6aa974d0f6@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org # v2.6.36+
Fixes: c19483cc5e56 ("bluetooth: Fix missing NULL check")
Fixes: b3190df62861 ("Bluetooth: Support for Atheros AR300x serial chip")
Fixes: 118612fb9165 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
Fixes: ff2895592f0f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")
Fixes: fa9ad876b8e0 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
---

out-of-commit-message-note:

I believe, this is a good location for the check. This way we protect protocols
which does not call tiocm[gs]et() or hci_uart_set_flow_control() but may
change to call them in the future.

Also we do not need hci_uart_has_tiocm_support() helper now.

 drivers/bluetooth/hci_ldisc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index c84f985f348d..4a85c51d0307 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -459,10 +459,11 @@ 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
+	/* Error if the tty has no write or tiocm[gs]et ops instead of leaving
+	 * an exploitable hole
 	 */
-	if (tty->ops->write == NULL)
+	if (tty->ops->write == NULL || tty->ops->tiocmget == NULL ||
+	    tty->ops->tiocmset == NULL)
 		return -EOPNOTSUPP;
 
 	hu = kzalloc(sizeof(struct hci_uart), GFP_KERNEL);
-- 
2.21.0

Re: [PATCH v2] Bluetooth: hci_ldisc: check for missing tty operations

[Marcel Holtmann]

Hi Vladis,

> Certain ttys operations (pty_unix98_ops) lack tiocmget() and tiocmset()
> functions which are called by the certain HCI UART protocols (hci_ath,
> hci_bcm, hci_intel, hci_mrvl, hci_qca) via hci_uart_set_flow_control()
> or directly. This leads to an execution at NULL and can be triggered by
> an unprivileged user. Fix this by adding a check for the missing tty
> operations the same way it is done for write().
> 
> This fixes CVE-2019-10207. The Fixes: lines list commits where calls to
> tiocm[gs]et() or hci_uart_set_flow_control() were added to the HCI UART
> protocols.
> 
> Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
> Reported-by: syzbot+79337b501d6aa974d0f6@syzkaller.appspotmail.com
> Cc: stable@vger.kernel.org # v2.6.36+
> Fixes: c19483cc5e56 ("bluetooth: Fix missing NULL check")
> Fixes: b3190df62861 ("Bluetooth: Support for Atheros AR300x serial chip")
> Fixes: 118612fb9165 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
> Fixes: ff2895592f0f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
> Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")
> Fixes: fa9ad876b8e0 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
> Signed-off-by: Vladis Dronov <vdronov@redhat.com>
> ---
> 
> out-of-commit-message-note:
> 
> I believe, this is a good location for the check. This way we protect protocols
> which does not call tiocm[gs]et() or hci_uart_set_flow_control() but may
> change to call them in the future.
> 
> Also we do not need hci_uart_has_tiocm_support() helper now.
> 
> drivers/bluetooth/hci_ldisc.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index c84f985f348d..4a85c51d0307 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -459,10 +459,11 @@ 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
> +	/* Error if the tty has no write or tiocm[gs]et ops instead of leaving
> +	 * an exploitable hole
> 	 */
> -	if (tty->ops->write == NULL)
> +	if (tty->ops->write == NULL || tty->ops->tiocmget == NULL ||
> +	    tty->ops->tiocmset == NULL)
> 		return -EOPNOTSUPP;

this means that you can not run hci_h4.c on any TTY anymore. For all the vendor specific ones, I agree, but H:4 is a Bluetooth SIG defined standard one that we might want to allow on any kind of TTY since it doesn’t really mandate anything.

So I would prefer if we go with a hci_uart_has_tiocm_support helper for now. 

Regards

Marcel

[PATCH v3] Bluetooth: hci_uart: check for missing tty operations

[Vladis Dronov]

Certain ttys operations (pty_unix98_ops) lack tiocmget() and tiocmset()
functions which are called by the certain HCI UART protocols (hci_ath,
hci_bcm, hci_intel, hci_mrvl, hci_qca) via hci_uart_set_flow_control()
or directly. This leads to an execution at NULL and can be triggered by
an unprivileged user. Fix this by adding a helper function and a check
for the missing tty operations in the protocols code.

This fixes CVE-2019-10207. The Fixes: lines list commits where calls to
tiocm[gs]et() or hci_uart_set_flow_control() were added to the HCI UART
protocols.

Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
Reported-by: syzbot+79337b501d6aa974d0f6@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org # v2.6.36+
Fixes: b3190df62861 ("Bluetooth: Support for Atheros AR300x serial chip")
Fixes: 118612fb9165 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
Fixes: ff2895592f0f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")
Fixes: fa9ad876b8e0 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
---

out-of-commit-message-note:

it is possible that a HCI UART protocol uses serial device's
operations and not a tty ones. i made hci_uart_has_flow_control() to
check this also, hence the name. serial device's code checks if
the needed operations are present itself.

i believe, hci_h5 does not need this check, as it uses serial device
functions only (as of now):

    serdev_device_set_flow_control(h5->hu->serdev, false);
    serdev_device_set_baudrate(h5->hu->serdev, 115200);

 drivers/bluetooth/hci_ath.c   | 3 +++
 drivers/bluetooth/hci_bcm.c   | 3 +++
 drivers/bluetooth/hci_intel.c | 3 +++
 drivers/bluetooth/hci_ldisc.c | 7 +++++++
 drivers/bluetooth/hci_mrvl.c  | 3 +++
 drivers/bluetooth/hci_qca.c   | 3 +++
 drivers/bluetooth/hci_uart.h  | 1 +
 7 files changed, 23 insertions(+)

diff --git a/drivers/bluetooth/hci_ath.c b/drivers/bluetooth/hci_ath.c
index a55be205b91a..dbfe34664633 100644
--- a/drivers/bluetooth/hci_ath.c
+++ b/drivers/bluetooth/hci_ath.c
@@ -98,6 +98,9 @@ static int ath_open(struct hci_uart *hu)
 
 	BT_DBG("hu %p", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	ath = kzalloc(sizeof(*ath), GFP_KERNEL);
 	if (!ath)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/hci_bcm.c b/drivers/bluetooth/hci_bcm.c
index 8905ad2edde7..ae2624fce913 100644
--- a/drivers/bluetooth/hci_bcm.c
+++ b/drivers/bluetooth/hci_bcm.c
@@ -406,6 +406,9 @@ static int bcm_open(struct hci_uart *hu)
 
 	bt_dev_dbg(hu->hdev, "hu %p", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	bcm = kzalloc(sizeof(*bcm), GFP_KERNEL);
 	if (!bcm)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/hci_intel.c b/drivers/bluetooth/hci_intel.c
index 207bae5e0d46..31f25153087d 100644
--- a/drivers/bluetooth/hci_intel.c
+++ b/drivers/bluetooth/hci_intel.c
@@ -391,6 +391,9 @@ static int intel_open(struct hci_uart *hu)
 
 	BT_DBG("hu %p", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	intel = kzalloc(sizeof(*intel), GFP_KERNEL);
 	if (!intel)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 8950e07889fe..11049e2336f3 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -292,6 +292,13 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
 	return 0;
 }
 
+/* Check the underlying device or tty has flow control support */
+bool hci_uart_has_flow_control(struct hci_uart *hu)
+{
+	return hu->serdev ||
+		(hu->tty->driver->ops->tiocmget && hu->tty->driver->ops->tiocmset);
+}
+
 /* Flow control or un-flow control the device */
 void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
 {
diff --git a/drivers/bluetooth/hci_mrvl.c b/drivers/bluetooth/hci_mrvl.c
index f98e5cc343b2..fbc3f7c3a5c7 100644
--- a/drivers/bluetooth/hci_mrvl.c
+++ b/drivers/bluetooth/hci_mrvl.c
@@ -59,6 +59,9 @@ static int mrvl_open(struct hci_uart *hu)
 
 	BT_DBG("hu %p", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	mrvl = kzalloc(sizeof(*mrvl), GFP_KERNEL);
 	if (!mrvl)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index 9a5c9c1f9484..82a0a3691a63 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -473,6 +473,9 @@ static int qca_open(struct hci_uart *hu)
 
 	BT_DBG("hu %p qca_open", hu);
 
+	if (!hci_uart_has_flow_control(hu))
+		return -EOPNOTSUPP;
+
 	qca = kzalloc(sizeof(struct qca_data), GFP_KERNEL);
 	if (!qca)
 		return -ENOMEM;
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index f11af3912ce6..6ab631101019 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -104,6 +104,7 @@ int hci_uart_wait_until_sent(struct hci_uart *hu);
 int hci_uart_init_ready(struct hci_uart *hu);
 void hci_uart_init_work(struct work_struct *work);
 void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed);
+bool hci_uart_has_flow_control(struct hci_uart *hu);
 void hci_uart_set_flow_control(struct hci_uart *hu, bool enable);
 void hci_uart_set_speeds(struct hci_uart *hu, unsigned int init_speed,
 			 unsigned int oper_speed);
-- 
2.20.1

Re: [PATCH v3] Bluetooth: hci_uart: check for missing tty operations

[Marcel Holtmann]

Hi Vladis,

> Certain ttys operations (pty_unix98_ops) lack tiocmget() and tiocmset()
> functions which are called by the certain HCI UART protocols (hci_ath,
> hci_bcm, hci_intel, hci_mrvl, hci_qca) via hci_uart_set_flow_control()
> or directly. This leads to an execution at NULL and can be triggered by
> an unprivileged user. Fix this by adding a helper function and a check
> for the missing tty operations in the protocols code.
> 
> This fixes CVE-2019-10207. The Fixes: lines list commits where calls to
> tiocm[gs]et() or hci_uart_set_flow_control() were added to the HCI UART
> protocols.
> 
> Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
> Reported-by: syzbot+79337b501d6aa974d0f6@syzkaller.appspotmail.com
> Cc: stable@vger.kernel.org # v2.6.36+
> Fixes: b3190df62861 ("Bluetooth: Support for Atheros AR300x serial chip")
> Fixes: 118612fb9165 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
> Fixes: ff2895592f0f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
> Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")
> Fixes: fa9ad876b8e0 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
> Signed-off-by: Vladis Dronov <vdronov@redhat.com>
> ---
> 
> out-of-commit-message-note:
> 
> it is possible that a HCI UART protocol uses serial device's
> operations and not a tty ones. i made hci_uart_has_flow_control() to
> check this also, hence the name. serial device's code checks if
> the needed operations are present itself.
> 
> i believe, hci_h5 does not need this check, as it uses serial device
> functions only (as of now):
> 
>    serdev_device_set_flow_control(h5->hu->serdev, false);
>    serdev_device_set_baudrate(h5->hu->serdev, 115200);
> 
> drivers/bluetooth/hci_ath.c   | 3 +++
> drivers/bluetooth/hci_bcm.c   | 3 +++
> drivers/bluetooth/hci_intel.c | 3 +++
> drivers/bluetooth/hci_ldisc.c | 7 +++++++
> drivers/bluetooth/hci_mrvl.c  | 3 +++
> drivers/bluetooth/hci_qca.c   | 3 +++
> drivers/bluetooth/hci_uart.h  | 1 +
> 7 files changed, 23 insertions(+)

I changed the hci_uart_has_flow_control function into using more readable separate checks and then send the patch directly to Linus.

Regards

Marcel