[PATCH 3.14 17/21] can: fix handling of unmodifiable configuration options fix

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: Oliver Hartkopp <socketcan@hartkopp.net>

commit bce271f255dae8335dc4d2ee2c4531e09cc67f5a upstream.

With upstream commit bb208f144cf3f59 (can: fix handling of unmodifiable
configuration options) a new can_validate() function was introduced.

When invoking 'ip link set can0 type can' without any configuration data
can_validate() tries to validate the content without taking into account that
there's totally no content. This patch adds a check for missing content.

Reported-by: ajneu <ajneu1@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/can/dev.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -665,6 +665,9 @@ static int can_changelink(struct net_dev
 		}
 	}
 
+	if (!data)
+		return 0;
+
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm;