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Subject[PATCH 4.14 004/164] serdev: ttyport: fix NULL-deref on hangup
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@kernel.org>

commit 8bcd4e6a8decac251d55c4377e2e67f052777ce0 upstream.

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: bed35c6dfa6a ("serdev: add a tty port controller driver")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serdev/serdev-ttyport.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -57,12 +57,19 @@ static void ttyport_write_wakeup(struct
{
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 = {

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