Bluetooth: hci_uart: check for missing tty operations

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: b3190df628 ("Bluetooth: Support for Atheros AR300x serial chip")
Fixes: 118612fb91 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
Fixes: ff2895592f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
Fixes: 162f812f23 ("Bluetooth: hci_uart: Add Marvell support")
Fixes: fa9ad876b8 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Yu-Chen, Cho <acho@suse.com>
Tested-by: Yu-Chen, Cho <acho@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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;

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;

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;

drivers/bluetooth/hci_ldisc.c

@@ -292,6 +292,19 @@ 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)
+{
+	/* serdev nodes check if the needed operations are present */
+	if (hu->serdev)
+		return true;
+
+	if (hu->tty->driver->ops->tiocmget && hu->tty->driver->ops->tiocmset)
+		return true;
+
+	return false;
+}
+
 /* Flow control or un-flow control the device */
 void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
 {

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;

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;

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);