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From: Shuah Khan <shuah@kernel.org>
To: marcel@holtmann.org, johan.hedberg@gmail.com, viro@zeniv.linux.org.uk
Cc: Shuah Khan <shuah@kernel.org>,
	gregkh@linuxfoundation.org, linux-bluetooth@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2] tty: Fix WARNING in tty_set_termios()
Date: Thu, 31 Jan 2019 16:23:59 -0700
Message-ID: <20190131232359.27948-1-shuah@kernel.org> (raw)

tty_set_termios() has the following WARN_ON which can be triggered with a
syscall to invoke TIOCSETD __NR_ioctl.

WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
                tty->driver->subtype == PTY_TYPE_MASTER);
Reference: https://syzkaller.appspot.com/bug?id=2410d22f1d8e5984217329dd0884b01d99e3e48d

The problem started with commit 7721383f4199 ("Bluetooth: hci_uart: Support
operational speed during setup") which introduced a new way for how
tty_set_termios() could end up being called for a master pty.

Fix the problem by preventing setting the HCI line discipline for PTYs
from hci_uart_setup() and hci_uart_set_flow_control().

The reproducer is used to reproduce the problem and verify the fix.

Reported-by: syzbot+a950165cbb86bdd023a4@syzkaller.appspotmail.com
Signed-off-by: Shuah Khan <shuah@kernel.org>
---
 drivers/bluetooth/hci_ldisc.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index fbf7b4df23ab..ce84ca91ca70 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -314,6 +314,11 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
 		return;
 	}
 
+	/* don't set HCI line discipline on PTYs */
+	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+	    tty->driver->subtype == PTY_TYPE_MASTER)
+		return;
+
 	if (enable) {
 		/* Disable hardware flow control */
 		ktermios = tty->termios;
@@ -384,11 +389,17 @@ void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed)
 static int hci_uart_setup(struct hci_dev *hdev)
 {
 	struct hci_uart *hu = hci_get_drvdata(hdev);
+	struct tty_struct *tty = hu->tty;
 	struct hci_rp_read_local_version *ver;
 	struct sk_buff *skb;
 	unsigned int speed;
 	int err;
 
+	/* don't set HCI line discipline on PTYs */
+	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+	    tty->driver->subtype == PTY_TYPE_MASTER)
+		return -EINVAL;
+
 	/* Init speed if any */
 	if (hu->init_speed)
 		speed = hu->init_speed;
-- 
2.17.1


             reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-31 23:23 Shuah Khan [this message]
2019-02-01  0:14 ` Greg KH
2019-02-01 23:21   ` shuah
2019-02-01  9:28 ` Johan Hovold
2019-02-01  9:36   ` Johan Hovold
2019-02-01 23:20   ` shuah
2019-02-01 10:00 ` Marcel Holtmann
2019-02-01 23:18   ` shuah

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