============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u8:2/5638 is trying to acquire lock:
ffff888105ee6958 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0

but task is already holding lock:
ffff88810dd92d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0

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

       CPU0
       ----
  lock(&qdisc_xmit_lock_key#4);
  lock(&qdisc_xmit_lock_key#4);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

16 locks held by kworker/u8:2/5638:
 #0: ffff888172bce148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0
 #1: ffffc90003ee7c40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0
 #2: ffffffff8fbd0c88 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x11e/0x14c0
 #3: ffff888034da3538 (&idev->mc_lock){+.+.}-{4:4}, at: ipv6_mc_dad_complete+0x32/0x540
 #4: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x213/0xe40
 #5: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550
 #6: ffffffff8e75e640 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x277/0x3890
 #7: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: bond_start_xmit+0xc9/0x1960
 #8: ffffffff8e75e640 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x277/0x3890
 #9: ffff888102ecb228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x101c/0x3890
 #10: ffff88810dd92d58 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0
 #11: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5b/0x450
 #12: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3c2/0x1070
 #13: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x23/0x270
 #14: ffffffff8e75e640 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x277/0x3890
 #15: ffff888024009228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x101c/0x3890

stack backtrace:
CPU: 0 UID: 0 PID: 5638 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_deadlock_bug+0x279/0x290
 __lock_acquire+0x253f/0x2cf0
 lock_acquire+0xf0/0x2e0
 _raw_spin_lock+0x2e/0x40
 sch_direct_xmit+0x15f/0x4c0
 __dev_queue_xmit+0x1550/0x3890
 NF_HOOK+0x33a/0x3c0
 arp_xmit+0x16c/0x270
 arp_solicit+0xbe0/0xe40
 __neigh_event_send+0xf05/0x1530
 neigh_resolve_output+0x198/0x750
 ip_finish_output2+0xca9/0x1070
 ip_output+0x29f/0x450
 iptunnel_xmit+0x616/0xca0
 ip_tunnel_xmit+0x193a/0x1f20
 __gre_xmit+0x19e/0x240
 erspan_xmit+0xa81/0x1670
 dev_hard_start_xmit+0x2d8/0x870
 sch_direct_xmit+0x251/0x4c0
 __dev_queue_xmit+0x1550/0x3890
 bond_start_xmit+0x77d/0x1960
 dev_hard_start_xmit+0x2d8/0x870
 __dev_queue_xmit+0x16d1/0x3890
 ip6_output+0x340/0x550
 NF_HOOK+0x177/0x4f0
 mld_sendpack+0x8b4/0xe40
 ipv6_mc_dad_complete+0x88/0x540
 addrconf_dad_completed+0x8a7/0xe60
 addrconf_dad_work+0xc5e/0x14c0
 process_scheduled_works+0xb6e/0x18c0
 worker_thread+0xa53/0xfc0
 kthread+0x388/0x470
 ret_from_fork+0x51e/0xb90
 ret_from_fork_asm+0x1a/0x30
 </TASK>
