[PATCH 3.16 135/157] Bluetooth: hci_uart: check for missing tty operations

[Ben Hutchings]

3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vladis Dronov <vdronov@xxxxxxxxxx>

commit b36a1552d7319bbfd5cf7f08726c23c5c66d4f73 upstream.

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@xxxxxxxxxxxxxxxxxxxxxxxxx
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@xxxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Reviewed-by: Yu-Chen, Cho <acho@xxxxxxxx>
Tested-by: Yu-Chen, Cho <acho@xxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16:
 - Only hci_ath is affected
 - There is no serdev support]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/drivers/bluetooth/hci_ath.c
+++ b/drivers/bluetooth/hci_ath.c
@@ -112,6 +112,9 @@ 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;
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -261,6 +261,15 @@ static int hci_uart_send_frame(struct hc
 	return 0;
 }
 
+/* Check the underlying device or tty has flow control support */
+bool hci_uart_has_flow_control(struct hci_uart *hu)
+{
+	if (hu->tty->driver->ops->tiocmget && hu->tty->driver->ops->tiocmset)
+		return true;
+
+	return false;
+}
+
 /* ------ LDISC part ------ */
 /* hci_uart_tty_open
  *
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -90,6 +90,7 @@ int hci_uart_register_proto(struct hci_u
 int hci_uart_unregister_proto(struct hci_uart_proto *p);
 int hci_uart_tx_wakeup(struct hci_uart *hu);
 int hci_uart_init_ready(struct hci_uart *hu);
+bool hci_uart_has_flow_control(struct hci_uart *hu);
 
 #ifdef CONFIG_BT_HCIUART_H4
 int h4_init(void);