[PATCHv2 net] bridge: check iface upper dev when setting master via ioctl

[Hangbin Liu <liuhangbin@gmail.com>]

When we set a bond slave's master to bridge via ioctl, we only check
the IFF_BRIDGE_PORT flag. Although we will find the slave's real master
at netdev_master_upper_dev_link() later, it already does some settings
and allocates some resources. It would be better to return as early
as possible.

v1 -> v2:
use netdev_master_upper_dev_get() instead of netdev_has_any_upper_dev()
to check if we have a master, because not all upper devs are masters,
e.g. vlan device.

Reported-by: syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 net/bridge/br_if.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 82c1a6f..5bb6681 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -518,8 +518,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
 		return -ELOOP;
 	}
 
-	/* Device is already being bridged */
-	if (br_port_exists(dev))
+	/* Device has master upper dev */
+	if (netdev_master_upper_dev_get(dev))
 		return -EBUSY;
 
 	/* No bridging devices that dislike that (e.g. wireless) */
-- 
2.5.5