[PATCH net] bonding: Fix warning in default_device_exit_batch()

[Shigeru Yoshida]

syzbot reported warning in default_device_exit_batch() like below [1]:

WARNING: CPU: 1 PID: 56 at net/core/dev.c:10867 unregister_netdevice_many_notify+0x14cf/0x19f0 net/core/dev.c:10867
...
Call Trace:
 <TASK>
 unregister_netdevice_many net/core/dev.c:10897 [inline]
 default_device_exit_batch+0x451/0x5b0 net/core/dev.c:11350
 ops_exit_list+0x125/0x170 net/core/net_namespace.c:174
 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613
 process_one_work+0x9bf/0x1820 kernel/workqueue.c:2390
 worker_thread+0x669/0x1090 kernel/workqueue.c:2537
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>

For bond devices which also has a master device, IFF_SLAVE flag is
cleared at err_undo_flags label in bond_enslave() if it is not
ARPHRD_ETHER type.  In this case, __bond_release_one() is not called
when bond_netdev_event() received NETDEV_UNREGISTER event.  This
causes the above warning.

This patch fixes this issue by setting IFF_SLAVE flag at
err_undo_flags label in bond_enslave() if the bond device has a master
device.

Fixes: 7d5cd2ce5292 ("bonding: correctly handle bonding type change on enslave failure")
Cc: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
Link: https://syzkaller.appspot.com/bug?id=391c7b1f6522182899efba27d891f1743e8eb3ef [1]
Reported-by: syzbot+9dfc3f3348729cc82277@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
---
 drivers/net/bonding/bond_main.c | 2 ++
 include/net/bonding.h           | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 00646aa315c3..1a8b59e1468d 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2291,6 +2291,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
 			dev_close(bond_dev);
 			ether_setup(bond_dev);
 			bond_dev->flags |= IFF_MASTER;
+			if (bond_has_master(bond))
+				bond_dev->flags |= IFF_SLAVE;
 			bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 		}
 	}
diff --git a/include/net/bonding.h b/include/net/bonding.h
index ea36ab7f9e72..ed0b49501fad 100644
--- a/include/net/bonding.h
+++ b/include/net/bonding.h
@@ -57,6 +57,11 @@
 
 #define bond_has_slaves(bond) !list_empty(bond_slave_list(bond))
 
+/* master list primitives */
+#define bond_master_list(bond) (&(bond)->dev->adj_list.upper)
+
+#define bond_has_master(bond) !list_empty(bond_master_list(bond))
+
 /* IMPORTANT: bond_first/last_slave can return NULL in case of an empty list */
 #define bond_first_slave(bond) \
 	(bond_has_slaves(bond) ? \
-- 
2.39.0