net: propagate errors correctly in register_netdevice()

If netdev_name_node_head_alloc() fails to allocate
memory, we absolutely want register_netdevice() to return
-ENOMEM instead of zero :/

One of the syzbot report looked like :

general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 8760 Comm: syz-executor839 Not tainted 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ovs_vport_add+0x185/0x500 net/openvswitch/vport.c:205
Code: 89 c6 e8 3e b6 3a fa 49 81 fc 00 f0 ff ff 0f 87 6d 02 00 00 e8 8c b4 3a fa 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 d3 02 00 00 49 8d 7c 24 08 49 8b 34 24 48 b8 00
RSP: 0018:ffff88808fe5f4e0 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: ffffffff89be8820 RCX: ffffffff87385162
RDX: 0000000000000000 RSI: ffffffff87385174 RDI: 0000000000000007
RBP: ffff88808fe5f510 R08: ffff8880933c6600 R09: fffffbfff14ee13c
R10: fffffbfff14ee13b R11: ffffffff8a7709df R12: 0000000000000004
R13: ffffffff89be8850 R14: ffff88808fe5f5e0 R15: 0000000000000002
FS:  0000000001d71880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000280 CR3: 0000000096e4c000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 new_vport+0x1b/0x1d0 net/openvswitch/datapath.c:194
 ovs_dp_cmd_new+0x5e5/0xe30 net/openvswitch/datapath.c:1644
 genl_family_rcv_msg+0x74b/0xf90 net/netlink/genetlink.c:629
 genl_rcv_msg+0xca/0x170 net/netlink/genetlink.c:654
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
 genl_rcv+0x29/0x40 net/netlink/genetlink.c:665
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x531/0x710 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x8a5/0xd60 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:657
 ___sys_sendmsg+0x803/0x920 net/socket.c:2311
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2356
 __do_sys_sendmsg net/socket.c:2365 [inline]
 __se_sys_sendmsg net/socket.c:2363 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2363

Fixes: ff927412 ("net: introduce name_node struct to be used in hashlist")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Tested-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -8935,6 +8935,7 @@ int register_netdevice(struct net_device *dev)
 	if (ret < 0)
 		goto out;
 
+	ret = -ENOMEM;
 	dev->name_node = netdev_name_node_head_alloc(dev);
 	if (!dev->name_node)
 		goto out;