team: prevent adding a device which is already a team device lower

Prevent adding a device which is already a team device lower,
e.g. adding veth0 if vlan1 was already added and veth0 is a lower of
vlan1.

This is not useful in practice and can lead to recursive locking:

$ ip link add veth0 type veth peer name veth1
$ ip link set veth0 up
$ ip link set veth1 up
$ ip link add link veth0 name veth0.1 type vlan protocol 802.1Q id 1
$ ip link add team0 type team
$ ip link set veth0.1 down
$ ip link set veth0.1 master team0
team0: Port device veth0.1 added
$ ip link set veth0 down
$ ip link set veth0 master team0

============================================
WARNING: possible recursive locking detected
6.13.0-rc2-virtme-00441-ga14a429069bb torvalds#46 Not tainted
--------------------------------------------
ip/7684 is trying to acquire lock:
ffff888016848e00 (team->team_lock_key){+.+.}-{4:4}, at: team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)

but task is already holding lock:
ffff888016848e00 (team->team_lock_key){+.+.}-{4:4}, at: team_add_slave (drivers/net/team/team_core.c:1147 drivers/net/team/team_core.c:1977)

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(team->team_lock_key);
lock(team->team_lock_key);

*** DEADLOCK ***

May be due to missing lock nesting notation

2 locks held by ip/7684:

stack backtrace:
CPU: 3 UID: 0 PID: 7684 Comm: ip Not tainted 6.13.0-rc2-virtme-00441-ga14a429069bb torvalds#46
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:122)
print_deadlock_bug.cold (kernel/locking/lockdep.c:3040)
__lock_acquire (kernel/locking/lockdep.c:3893 kernel/locking/lockdep.c:5226)
? netlink_broadcast_filtered (net/netlink/af_netlink.c:1548)
lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 2))
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
? lock_acquire (kernel/locking/lockdep.c:5822)
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
__mutex_lock (kernel/locking/mutex.c:587 kernel/locking/mutex.c:735)
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
? fib_sync_up (net/ipv4/fib_semantics.c:2167)
? team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
team_device_event (drivers/net/team/team_core.c:2928 drivers/net/team/team_core.c:2951 drivers/net/team/team_core.c:2973)
notifier_call_chain (kernel/notifier.c:85)
call_netdevice_notifiers_info (net/core/dev.c:1996)
__dev_notify_flags (net/core/dev.c:8993)
? __dev_change_flags (net/core/dev.c:8975)
dev_change_flags (net/core/dev.c:9027)
vlan_device_event (net/8021q/vlan.c:85 net/8021q/vlan.c:470)
? br_device_event (net/bridge/br.c:143)
notifier_call_chain (kernel/notifier.c:85)
call_netdevice_notifiers_info (net/core/dev.c:1996)
dev_open (net/core/dev.c:1519 net/core/dev.c:1505)
team_add_slave (drivers/net/team/team_core.c:1219 drivers/net/team/team_core.c:1977)
? __pfx_team_add_slave (drivers/net/team/team_core.c:1972)
do_set_master (net/core/rtnetlink.c:2917)
do_setlink.isra.0 (net/core/rtnetlink.c:3117)

Reported-by: syzbot+3c47b5843403a45aef57@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3c47b5843403a45aef57
Fixes: 3d249d4 ("net: introduce ethernet teaming device")
Signed-off-by: Octavian Purdila <tavip@google.com>
Signed-off-by: NipaLocal <nipa@local>

drivers/net/team/team_core.c

@@ -1175,6 +1175,13 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
 		return -EBUSY;
 	}
 
+	if (netdev_has_upper_dev(port_dev, dev)) {
+		NL_SET_ERR_MSG(extack, "Device is already a lower device of the team interface");
+		netdev_err(dev, "Device %s is already a lower device of the team interface\n",
+			   portname);
+		return -EBUSY;
+	}
+
 	if (port_dev->features & NETIF_F_VLAN_CHALLENGED &&
 	    vlan_uses_dev(dev)) {
 		NL_SET_ERR_MSG(extack, "Device is VLAN challenged and team device has VLAN set up");