[PATCH net] net: bridge: Fix a warning when del bridge sysfs

[Wang Hai <wanghai38@huawei.com>]

If adding bridge sysfs fails, br->ifobj will be NULL, there is no
need to delete its non-existent sysfs when deleting the bridge device,
otherwise, it will cause a warning. So, when br->ifobj == NULL,
directly return can fix this bug.

br_sysfs_addbr: can't create group bridge4/bridge
------------[ cut here ]------------
sysfs group 'bridge' not found for kobject 'bridge4'
WARNING: CPU: 2 PID: 9004 at fs/sysfs/group.c:279 sysfs_remove_group fs/sysfs/group.c:279 [inline]
WARNING: CPU: 2 PID: 9004 at fs/sysfs/group.c:279 sysfs_remove_group+0x153/0x1b0 fs/sysfs/group.c:270
Modules linked in: iptable_nat
...
Call Trace:
  br_dev_delete+0x112/0x190 net/bridge/br_if.c:384
  br_dev_newlink net/bridge/br_netlink.c:1381 [inline]
  br_dev_newlink+0xdb/0x100 net/bridge/br_netlink.c:1362
  __rtnl_newlink+0xe11/0x13f0 net/core/rtnetlink.c:3441
  rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3500
  rtnetlink_rcv_msg+0x385/0x980 net/core/rtnetlink.c:5562
  netlink_rcv_skb+0x134/0x3d0 net/netlink/af_netlink.c:2494
  netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
  netlink_unicast+0x4a0/0x6a0 net/netlink/af_netlink.c:1330
  netlink_sendmsg+0x793/0xc80 net/netlink/af_netlink.c:1919
  sock_sendmsg_nosec net/socket.c:651 [inline]
  sock_sendmsg+0x139/0x170 net/socket.c:671
  ____sys_sendmsg+0x658/0x7d0 net/socket.c:2353
  ___sys_sendmsg+0xf8/0x170 net/socket.c:2407
  __sys_sendmsg+0xd3/0x190 net/socket.c:2440
  do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
---
 net/bridge/br_sysfs_br.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index 7db06e3f642a..1e9cbf31d904 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -991,6 +991,9 @@ void br_sysfs_delbr(struct net_device *dev)
 	struct kobject *kobj = &dev->dev.kobj;
 	struct net_bridge *br = netdev_priv(dev);
 
+	if (!br->ifobj)
+		return;
+
 	kobject_put(br->ifobj);
 	sysfs_remove_bin_file(kobj, &bridge_forward);
 	sysfs_remove_group(kobj, &bridge_group);
-- 
2.17.1