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 it by by preventing setting the HCI line discipline for PTYs in
hci_uart_tty_open().
Reported-by: syzbot+a950165cbb86bdd023a4@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Johan Hovold <johan@xxxxxxxxxx>
Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Shuah Khan <shuah@xxxxxxxxxx>
---
drivers/bluetooth/hci_ldisc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index fbf7b4df23ab..c8faa4759cb7 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -475,9 +475,9 @@ static int hci_uart_tty_open(struct tty_struct *tty)
BT_DBG("tty %p", tty);
/* Error if the tty has no write op instead of leaving an exploitable
- * hole
+ * hole. In addition check if setting HCI line discipline is allowed.
*/
- if (tty->ops->write == NULL)
+ if (tty->ops->write == NULL || tty->ops->set_termios == NULL)
return -EOPNOTSUPP;
hu = kzalloc(sizeof(struct hci_uart), GFP_KERNEL);
--
2.17.1
