[patch added to 3.12-stable] can: fix handling of unmodifiable configuration options fix

[Jiri Slaby <jslaby@suse.cz>]

From: Oliver Hartkopp <socketcan@hartkopp.net>

This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.

===============

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: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/can/dev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index f66aeb79abdf..3c1a7f8211be 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -644,6 +644,9 @@ static int can_changelink(struct net_device *dev,
 	/* We need synchronization with dev->stop() */
 	ASSERT_RTNL();
 
+	if (!data)
+		return 0;
+
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm;
 
-- 
2.9.3