[PATCH 4.9 011/125] NFC: nfcmrvl_uart: add missing tty-device sanity check

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit 15e0c59f1535926a939d1df66d6edcf997d7c1b9 upstream.

Make sure to check the tty-device pointer before trying to access the
parent device to avoid dereferencing a NULL-pointer when the tty is one
end of a Unix98 pty.

Fixes: e097dc624f78 ("NFC: nfcmrvl: add UART driver")
Cc: Vincent Cuissard <cuissard@xxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Samuel Ortiz <sameo@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/nfc/nfcmrvl/uart.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/nfc/nfcmrvl/uart.c
+++ b/drivers/nfc/nfcmrvl/uart.c
@@ -109,6 +109,7 @@ static int nfcmrvl_nci_uart_open(struct
 	struct nfcmrvl_private *priv;
 	struct nfcmrvl_platform_data *pdata = NULL;
 	struct nfcmrvl_platform_data config;
+	struct device *dev = nu->tty->dev;
 
 	/*
 	 * Platform data cannot be used here since usually it is already used
@@ -116,9 +117,8 @@ static int nfcmrvl_nci_uart_open(struct
 	 * and check if DT entries were added.
 	 */
 
-	if (nu->tty->dev->parent && nu->tty->dev->parent->of_node)
-		if (nfcmrvl_uart_parse_dt(nu->tty->dev->parent->of_node,
-					  &config) == 0)
+	if (dev && dev->parent && dev->parent->of_node)
+		if (nfcmrvl_uart_parse_dt(dev->parent->of_node, &config) == 0)
 			pdata = &config;
 
 	if (!pdata) {
@@ -131,7 +131,7 @@ static int nfcmrvl_nci_uart_open(struct
 	}
 
 	priv = nfcmrvl_nci_register_dev(NFCMRVL_PHY_UART, nu, &uart_ops,
-					nu->tty->dev, pdata);
+					dev, pdata);
 	if (IS_ERR(priv))
 		return PTR_ERR(priv);