============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- kworker/0:7/4238 is trying to acquire lock: ffff888074d14218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff888074d14218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3922 [inline] ffff888074d14218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x1e69/0x2e50 net/core/dev.c:4266 but task is already holding lock: ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x108d/0x2e50 net/core/dev.c:4266 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); *** DEADLOCK *** May be due to missing lock nesting notation 14 locks held by kworker/0:7/4238: #0: ffff88802b3e7138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1 #1: ffffc900031dfd00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285 #2: ffffffff8d44b148 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1530 net/ipv6/addrconf.c:4113 #3: ffff88807ebc9530 (&idev->mc_lock){+.+.}-{3:3}, at: ipv6_mc_dad_complete+0x2d/0x4b0 net/ipv6/mcast.c:2249 #4: ffffffff8c31ef20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 #5: ffffffff8c31ef80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #6: ffffffff8c31ef80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #7: ffffffff8c31ef20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 #8: ffffffff8c31ef80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #9: ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] #9: ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #9: ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] #9: ffff888077d97258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x108d/0x2e50 net/core/dev.c:4266 #10: ffff88801fc8c098 (_xmit_ETHER#2){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #10: ffff88801fc8c098 (_xmit_ETHER#2){+.-.}-{2:2}, at: __netif_tx_lock include/linux/netdevice.h:4446 [inline] #10: ffff88801fc8c098 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x162/0x4a0 net/sched/sch_generic.c:343 #11: ffffffff8c31ef20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #12: ffffffff8c31ef80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #13: ffffffff8c31ef80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 stack backtrace: CPU: 0 PID: 4238 Comm: kworker/0:7 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 __lock_acquire+0x1247/0x7b50 kernel/locking/lockdep.c:-1 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:364 [inline] __dev_xmit_skb net/core/dev.c:3922 [inline] __dev_queue_xmit+0x1e69/0x2e50 net/core/dev.c:4266 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xc77/0x10e0 net/ipv4/ip_output.c:228 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip_output+0x2ba/0x3e0 net/ipv4/ip_output.c:434 iptunnel_xmit+0x4a1/0x8b0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1b4a/0x22f0 net/ipv4/ip_tunnel.c:824 __gre_xmit net/ipv4/ip_gre.c:474 [inline] erspan_xmit+0x9b9/0x15a0 net/ipv4/ip_gre.c:723 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x297/0x7d0 net/core/dev.c:3678 sch_direct_xmit+0x24d/0x4a0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:3897 [inline] __dev_queue_xmit+0x1694/0x2e50 net/core/dev.c:4266 bond_dev_queue_xmit+0x112/0x1e0 drivers/net/bonding/bond_main.c:304 __bond_start_xmit drivers/net/bonding/bond_main.c:5164 [inline] bond_start_xmit+0xd91/0x1a50 drivers/net/bonding/bond_main.c:5186 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x297/0x7d0 net/core/dev.c:3678 __dev_queue_xmit+0x195d/0x2e50 net/core/dev.c:4305 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip6_finish_output2+0x1052/0x1530 net/ipv6/ip6_output.c:130 dst_output include/net/dst.h:452 [inline] NF_HOOK+0x163/0x460 include/linux/netfilter.h:302 mld_sendpack+0x6ee/0xc40 net/ipv6/mcast.c:1825 ipv6_mc_dad_complete+0x83/0x4b0 net/ipv6/mcast.c:2252 addrconf_dad_completed+0x673/0xc80 net/ipv6/addrconf.c:4258 addrconf_dad_work+0xc83/0x1530 net/ipv6/addrconf.c:-1 process_one_work+0x867/0xff0 kernel/workqueue.c:2310 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457 kthread+0x42e/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog