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

[Vladis Dronov]

Certain ttys lack operations (eg: pty_unix98_ops) which still can be
called by certain hci uart proto (eg: mrvl, ath). Currently this leads
to execution at address 0x0. Fix this by adding checks for missing tty
operations.

Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
Reported-by: syzbot+79337b501d6aa974d0f6@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v2.6.39+
Signed-off-by: Vladis Dronov <vdronov@xxxxxxxxxx>
---
 drivers/bluetooth/hci_ath.c   |  7 ++++-
 drivers/bluetooth/hci_ldisc.c | 58 ++++++++++++++++++++---------------
 2 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/drivers/bluetooth/hci_ath.c b/drivers/bluetooth/hci_ath.c
index a55be205b91a..92d9bded5880 100644
--- a/drivers/bluetooth/hci_ath.c
+++ b/drivers/bluetooth/hci_ath.c
@@ -49,7 +49,12 @@ struct ath_vendor_cmd {
 
 static int ath_wakeup_ar3k(struct tty_struct *tty)
 {
-	int status = tty->driver->ops->tiocmget(tty);
+	int status;
+
+	if (!(tty->driver->ops->tiocmget && tty->driver->ops->tiocmset))
+		return TIOCM_CTS;
+
+	status = tty->driver->ops->tiocmget(tty);
 
 	if (status & TIOCM_CTS)
 		return status;
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index c84f985f348d..29b4970f9bca 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -307,32 +307,40 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
 		BT_DBG("Disabling hardware flow control: %s",
 		       status ? "failed" : "success");
 
-		/* Clear RTS to prevent the device from sending */
-		/* Most UARTs need OUT2 to enable interrupts */
-		status = tty->driver->ops->tiocmget(tty);
-		BT_DBG("Current tiocm 0x%x", status);
-
-		set &= ~(TIOCM_OUT2 | TIOCM_RTS);
-		clear = ~set;
-		set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
-		       TIOCM_OUT2 | TIOCM_LOOP;
-		clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
-			 TIOCM_OUT2 | TIOCM_LOOP;
-		status = tty->driver->ops->tiocmset(tty, set, clear);
-		BT_DBG("Clearing RTS: %s", status ? "failed" : "success");
+		if (tty->driver->ops->tiocmget && tty->driver->ops->tiocmset) {
+			/* Clear RTS to prevent the device from sending */
+			/* Most UARTs need OUT2 to enable interrupts */
+			status = tty->driver->ops->tiocmget(tty);
+			BT_DBG("Current tiocm 0x%x", status);
+
+			set &= ~(TIOCM_OUT2 | TIOCM_RTS);
+			clear = ~set;
+			set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
+			       TIOCM_OUT2 | TIOCM_LOOP;
+			clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
+			         TIOCM_OUT2 | TIOCM_LOOP;
+			status = tty->driver->ops->tiocmset(tty, set, clear);
+			BT_DBG("Clearing RTS: %s",
+			       status ? "failed" : "success");
+		} else
+			BT_DBG("Terminal RTS control is not present");
 	} else {
-		/* Set RTS to allow the device to send again */
-		status = tty->driver->ops->tiocmget(tty);
-		BT_DBG("Current tiocm 0x%x", status);
-
-		set |= (TIOCM_OUT2 | TIOCM_RTS);
-		clear = ~set;
-		set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
-		       TIOCM_OUT2 | TIOCM_LOOP;
-		clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
-			 TIOCM_OUT2 | TIOCM_LOOP;
-		status = tty->driver->ops->tiocmset(tty, set, clear);
-		BT_DBG("Setting RTS: %s", status ? "failed" : "success");
+		if (tty->driver->ops->tiocmget && tty->driver->ops->tiocmset) {
+			/* Set RTS to allow the device to send again */
+			status = tty->driver->ops->tiocmget(tty);
+			BT_DBG("Current tiocm 0x%x", status);
+
+			set |= (TIOCM_OUT2 | TIOCM_RTS);
+			clear = ~set;
+			set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
+			       TIOCM_OUT2 | TIOCM_LOOP;
+			clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
+			         TIOCM_OUT2 | TIOCM_LOOP;
+			status = tty->driver->ops->tiocmset(tty, set, clear);
+			BT_DBG("Setting RTS: %s",
+			       status ? "failed" : "success");
+		} else
+			BT_DBG("Terminal RTS control is not present");
 
 		/* Re-enable hardware flow control */
 		ktermios = tty->termios;
-- 
2.20.1