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serdev: ttyport: fix NULL-deref on hangup 

Make sure to use a properly refcounted tty_struct in write_wake up to
avoid dereferencing a NULL-pointer when a port is being hung up.

Fixes: bed35c6dfa ("serdev: add a tty port controller driver")
Cc: stable <stable@vger.kernel.org>     # 4.11
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2017-11-03 15:30:55 +01:00 committed by Greg Kroah-Hartman
parent fd00cf81a9
commit 8bcd4e6a8d
1 changed files with 9 additions and 2 deletions
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11
drivers/tty/serdev/serdev-ttyport.c
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@ -49,12 +49,19 @@ static void ttyport_write_wakeup(struct tty_port *port)
{
struct serdev_controller *ctrl = port->client_data;
struct serport *serport = serdev_controller_get_drvdata(ctrl);
struct tty_struct *tty;
if (test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &port->tty->flags) &&
tty = tty_port_tty_get(port);
if (!tty)
return;
if (test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags) &&
test_bit(SERPORT_ACTIVE, &serport->flags))
serdev_controller_write_wakeup(ctrl);
wake_up_interruptible_poll(&port->tty->write_wait, POLLOUT);
wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
tty_kref_put(tty);
}
static const struct tty_port_client_operations client_ops = {