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Subject[PATCH v2] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()
tty_set_termios() should be called with slave side of pty driver. So, If
tty driver is pty master, it needs to be switched to ->link.

Reported-by: syzbot+a950165cbb86bdd023a4@syzkaller.appspotmail.com
Signed-off-by: Myungho Jung <mhjungk@gmail.com>
---
drivers/bluetooth/hci_ldisc.c | 27 ++++++++++++++++++++++-----
1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index fbf7b4df23ab..0f6e70ea1dc3 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -299,10 +299,21 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
return 0;
}

+/* If pty master, return slave side */
+static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
+{
+ if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+ tty->driver->subtype == PTY_TYPE_MASTER)
+ tty->link;
+
+ return tty;
+}
+
/* Flow control or un-flow control the device */
void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
{
struct tty_struct *tty = hu->tty;
+ struct tty_struct *real_tty;
struct ktermios ktermios;
int status;
unsigned int set = 0;
@@ -314,11 +325,14 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
return;
}

+ /* termios should be set from slave side if tty driver is pty */
+ real_tty = hci_uart_get_real_tty(tty);
+
if (enable) {
/* Disable hardware flow control */
- ktermios = tty->termios;
+ ktermios = real_tty->termios;
ktermios.c_cflag &= ~CRTSCTS;
- status = tty_set_termios(tty, &ktermios);
+ status = tty_set_termios(real_tty, &ktermios);
BT_DBG("Disabling hardware flow control: %s",
status ? "failed" : "success");

@@ -350,9 +364,9 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
BT_DBG("Setting RTS: %s", status ? "failed" : "success");

/* Re-enable hardware flow control */
- ktermios = tty->termios;
+ ktermios = real_tty->termios;
ktermios.c_cflag |= CRTSCTS;
- status = tty_set_termios(tty, &ktermios);
+ status = tty_set_termios(real_tty, &ktermios);
BT_DBG("Enabling hardware flow control: %s",
status ? "failed" : "success");
}
@@ -367,9 +381,12 @@ void hci_uart_set_speeds(struct hci_uart *hu, unsigned int init_speed,

void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed)
{
- struct tty_struct *tty = hu->tty;
+ struct tty_struct *tty;
struct ktermios ktermios;

+ /* termios should be set from slave side if tty driver is pty */
+ tty = hci_uart_get_real_tty(hu->tty);
+
ktermios = tty->termios;
ktermios.c_cflag &= ~CBAUD;
tty_termios_encode_baud_rate(&ktermios, speed, speed);
--
2.17.1
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