hsr: fix interface leak in error path of hsr_dev_finalize()

To release hsr(upper) interface, it should release
its own lower interfaces first.
Then, hsr(upper) interface can be released safely.
In the current code of error path of hsr_dev_finalize(), it releases hsr
interface before releasing a lower interface.
So, a warning occurs, which warns about the leak of lower interfaces.
In order to fix this problem, changing the ordering of the error path of
hsr_dev_finalize() is needed.

Test commands:
    ip link add dummy0 type dummy
    ip link add dummy1 type dummy
    ip link add dummy2 type dummy
    ip link add hsr0 type hsr slave1 dummy0 slave2 dummy1
    ip link add hsr1 type hsr slave1 dummy2 slave2 dummy0

Splat looks like:
[  214.923127][    C2] WARNING: CPU: 2 PID: 1093 at net/core/dev.c:8992 rollback_registered_many+0x986/0xcf0
[  214.923129][    C2] Modules linked in: hsr dummy openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipx
[  214.923154][    C2] CPU: 2 PID: 1093 Comm: ip Not tainted 5.8.0-rc2+ #623
[  214.923156][    C2] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[  214.923157][    C2] RIP: 0010:rollback_registered_many+0x986/0xcf0
[  214.923160][    C2] Code: 41 8b 4e cc 45 31 c0 31 d2 4c 89 ee 48 89 df e8 e0 47 ff ff 85 c0 0f 84 cd fc ff ff 5
[  214.923162][    C2] RSP: 0018:ffff8880c5156f28 EFLAGS: 00010287
[  214.923165][    C2] RAX: ffff8880d1dad458 RBX: ffff8880bd1b9000 RCX: ffffffffb929d243
[  214.923167][    C2] RDX: 1ffffffff77e63f0 RSI: 0000000000000008 RDI: ffffffffbbf31f80
[  214.923168][    C2] RBP: dffffc0000000000 R08: fffffbfff77e63f1 R09: fffffbfff77e63f1
[  214.923170][    C2] R10: ffffffffbbf31f87 R11: 0000000000000001 R12: ffff8880c51570a0
[  214.923172][    C2] R13: ffff8880bd1b90b8 R14: ffff8880c5157048 R15: ffff8880d1dacc40
[  214.923174][    C2] FS:  00007fdd257a20c0(0000) GS:ffff8880da200000(0000) knlGS:0000000000000000
[  214.923175][    C2] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  214.923177][    C2] CR2: 00007ffd78beb038 CR3: 00000000be544005 CR4: 00000000000606e0
[  214.923179][    C2] Call Trace:
[  214.923180][    C2]  ? netif_set_real_num_tx_queues+0x780/0x780
[  214.923182][    C2]  ? dev_validate_mtu+0x140/0x140
[  214.923183][    C2]  ? synchronize_rcu.part.79+0x85/0xd0
[  214.923185][    C2]  ? synchronize_rcu_expedited+0xbb0/0xbb0
[  214.923187][    C2]  rollback_registered+0xc8/0x170
[  214.923188][    C2]  ? rollback_registered_many+0xcf0/0xcf0
[  214.923190][    C2]  unregister_netdevice_queue+0x18b/0x240
[  214.923191][    C2]  hsr_dev_finalize+0x56e/0x6e0 [hsr]
[  214.923192][    C2]  hsr_newlink+0x36b/0x450 [hsr]
[  214.923194][    C2]  ? hsr_dellink+0x70/0x70 [hsr]
[  214.923195][    C2]  ? rtnl_create_link+0x2e4/0xb00
[  214.923197][    C2]  ? __netlink_ns_capable+0xc3/0xf0
[  214.923198][    C2]  __rtnl_newlink+0xbdb/0x1270
[ ... ]

Fixes: e0a4b997 ("hsr: use upper/lower device infrastructure")
Reported-by: syzbot+7f1c020f68dab95aab59@syzkaller.appspotmail.com
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/hsr/hsr_device.c

@@ -415,6 +415,7 @@ int hsr_dev_finalize(struct net_device *hsr_dev, struct net_device *slave[2],
 		     unsigned char multicast_spec, u8 protocol_version,
 		     struct netlink_ext_ack *extack)
 {
+	bool unregister = false;
 	struct hsr_priv *hsr;
 	int res;
 
@@ -466,25 +467,27 @@ int hsr_dev_finalize(struct net_device *hsr_dev, struct net_device *slave[2],
 	if (res)
 		goto err_unregister;
 
+	unregister = true;
+
 	res = hsr_add_port(hsr, slave[0], HSR_PT_SLAVE_A, extack);
 	if (res)
-		goto err_add_slaves;
+		goto err_unregister;
 
 	res = hsr_add_port(hsr, slave[1], HSR_PT_SLAVE_B, extack);
 	if (res)
-		goto err_add_slaves;
+		goto err_unregister;
 
 	hsr_debugfs_init(hsr, hsr_dev);
 	mod_timer(&hsr->prune_timer, jiffies + msecs_to_jiffies(PRUNE_PERIOD));
 
 	return 0;
 
-err_add_slaves:
-	unregister_netdevice(hsr_dev);
 err_unregister:
 	hsr_del_ports(hsr);
 err_add_master:
 	hsr_del_self_node(hsr);
 
+	if (unregister)
+		unregister_netdevice(hsr_dev);
 	return res;
 }