Bluetooth: hci_uart: check for missing tty operations

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@syzkaller.appspotmail.com>
Cc: stable@vger.kernel.org # v2.6.36+
Fixes: b3190df6 ("Bluetooth: Support for Atheros AR300x serial chip")
Fixes: 118612fb ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
Fixes: ff289559 ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
Fixes: 162f812f ("Bluetooth: hci_uart: Add Marvell support")
Fixes: fa9ad876

 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Yu-Chen, Cho <acho@suse.com>
Tested-by: Yu-Chen, Cho <acho@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>