[PATCH] tty: serial: fsl_lpuart: potential NULL dereference

[Alexey Khoroshilov]

tty_port_tty_get() might return a tty which is NULL
if the port is not associated with a tty
(e.g. due to close or hangup).
But lpuart_start_rx_dma() dereferences tty without any check.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshi...@ispras.ru>
---
 drivers/tty/serial/fsl_lpuart.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 76103f2c4a80..9945b37c914a 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -833,9 +833,16 @@ 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 ktermios *termios = &tty->termios;
+       struct tty_struct *tty;
+       struct ktermios *termios;
 
+       tty = tty_port_tty_get(&sport->port.state->port);
+       if (!tty) {
+               dev_err(sport->port.dev, "Port is not associated with a tty\n");
+               return -ENODEV;
+       }
+
+       termios = &tty->termios;
        baud = tty_get_baud_rate(tty);
 
        bits = (termios->c_cflag & CSIZE) == CS7 ? 9 : 10;
-- 
2.7.4