[PATCH 4.18 118/350] failover: Add missing check to validate slave_dev in net_failover_slave_unregister

[Greg Kroah-Hartman]

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

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

From: YueHaibing <yuehaibing@xxxxxxxxxx>

[ Upstream commit 9e7e6cabf371cc008cb2244a04c012b516753693 ]

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/net_failover.c: In function 'net_failover_slave_unregister':
drivers/net/net_failover.c:598:35: warning:
 variable 'primary_dev' set but not used [-Wunused-but-set-variable]

There should check the validity of 'slave_dev'.

Fixes: cfc80d9a1163 ("net: Introduce net_failover driver")

Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
Acked-by: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/net_failover.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/net_failover.c
+++ b/drivers/net/net_failover.c
@@ -602,6 +602,9 @@ static int net_failover_slave_unregister
 	primary_dev = rtnl_dereference(nfo_info->primary_dev);
 	standby_dev = rtnl_dereference(nfo_info->standby_dev);
 
+	if (WARN_ON_ONCE(slave_dev != primary_dev && slave_dev != standby_dev))
+		return -ENODEV;
+
 	vlan_vids_del_by_dev(slave_dev, failover_dev);
 	dev_uc_unsync(slave_dev, failover_dev);
 	dev_mc_unsync(slave_dev, failover_dev);