tty: serial: lpuart: avoid leaking struct tty_struct

BugLink: https://bugs.launchpad.net/bugs/1836287
commit 3216c622a24b0ebb9c159a8d1daf7f17a106b3f5 upstream.

The function tty_port_tty_get() gets a reference to the tty. Since
the code is not using tty_port_tty_set(), the reference is kept
even after closing the tty.

Avoid using tty_port_tty_get() by directly access the tty instance.
Since lpuart_start_rx_dma() is called from the .startup() and
.set_termios() callback, it is safe to assume the tty instance is
valid.

Cc: stable@vger.kernel.org # v4.9+
Fixes: 5887ad43ee02 ("tty: serial: fsl_lpuart: Use cyclic DMA for Rx")
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 6a3df7ff8f4ff46b177c4124d2c17c5dd5bf63c7..82059055b22e1348f1c7160fba46f15a5dc39226 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -979,7 +979,8 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
        struct circ_buf *ring = &sport->rx_ring;
        int ret, nent;
        int bits, baud;
-       struct tty_struct *tty = tty_port_tty_get(&sport->port.state->port);
+       struct tty_port *port = &sport->port.state->port;
+       struct tty_struct *tty = port->tty;
        struct ktermios *termios = &tty->termios;
 
        baud = tty_get_baud_rate(tty);