============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- kworker/0:1/26243 is trying to acquire lock: ffff888025ed8318 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] ffff888025ed8318 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4186 [inline] ffff888025ed8318 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0xd58/0x3b70 net/core/dev.c:4729 but task is already holding lock: ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:197 [inline] ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4139 [inline] ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0x1370/0x3b70 net/core/dev.c:4729 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3); *** DEADLOCK *** May be due to missing lock nesting notation 21 locks held by kworker/0:1/26243: #0: ffff88814d692938 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline] #0: ffff88814d692938 ((wq_completion)mld){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346 #1: ffffc9001d6c7ba0 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline] #1: ffffc9001d6c7ba0 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346 #2: ffff888035930628 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x2d/0xd60 net/ipv6/mcast.c:2692 #3: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #3: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #3: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x1e7/0xe60 net/ipv6/mcast.c:1827 #4: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #4: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:235 #5: ffffffff8d44aca0 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #6: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #7: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #7: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #7: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x26f/0x3b70 net/core/dev.c:4688 #8: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #8: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #8: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: bond_start_xmit+0xf8/0x1a10 drivers/net/bonding/bond_main.c:5577 #9: ffffffff8d44aca0 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #10: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #10: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #10: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x26f/0x3b70 net/core/dev.c:4688 #11: ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:197 [inline] #11: ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4139 [inline] #11: ffff888037c96398 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0x1370/0x3b70 net/core/dev.c:4729 #12: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #12: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #12: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: __rt_spin_trylock kernel/locking/spinlock_rt.c:110 [inline] #12: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rt_spin_trylock+0x10d/0x2b0 kernel/locking/spinlock_rt.c:118 #13: ffff88805a136198 (&qdisc_xmit_lock_key#4){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] #13: ffff88805a136198 (&qdisc_xmit_lock_key#4){+...}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4685 [inline] #13: ffff88805a136198 (&qdisc_xmit_lock_key#4){+...}-{3:3}, at: sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:345 #14: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #14: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #14: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline] #14: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1c1/0x3e0 kernel/locking/spinlock_rt.c:57 #15: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #15: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #15: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5b/0x450 net/ipv4/ip_output.c:433 #16: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #16: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #16: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x452/0x11d0 net/ipv4/ip_output.c:230 #17: ffffffff8d44aca0 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #18: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #18: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #18: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x23/0x270 net/ipv4/arp.c:662 #19: ffffffff8d44aca0 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x540 kernel/softirq.c:163 #20: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #20: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #20: ffffffff8d5aa8e0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x26f/0x3b70 net/core/dev.c:4688 stack backtrace: CPU: 0 UID: 0 PID: 26243 Comm: kworker/0:1 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: mld mld_ifc_work Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3895 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] __dev_xmit_skb net/core/dev.c:4186 [inline] __dev_queue_xmit+0xd58/0x3b70 net/core/dev.c:4729 NF_HOOK+0x310/0x3a0 include/linux/netfilter.h:-1 arp_xmit+0x16c/0x270 net/ipv4/arp.c:664 arp_solicit+0xc6a/0xeb0 net/ipv4/arp.c:392 neigh_probe net/core/neighbour.c:1098 [inline] __neigh_event_send+0xf68/0x1580 net/core/neighbour.c:1271 neigh_event_send_probe include/net/neighbour.h:471 [inline] neigh_event_send include/net/neighbour.h:477 [inline] neigh_resolve_output+0x19f/0x780 net/core/neighbour.c:1579 neigh_output include/net/neighbour.h:547 [inline] ip_finish_output2+0xd97/0x11d0 net/ipv4/ip_output.c:237 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x29f/0x450 net/ipv4/ip_output.c:438 iptunnel_xmit+0x5f8/0xa90 net/ipv4/ip_tunnel_core.c:84 ip_tunnel_xmit+0x1c44/0x2390 net/ipv4/ip_tunnel.c:845 __gre_xmit net/ipv4/ip_gre.c:488 [inline] gre_tap_xmit+0x590/0x7a0 net/ipv4/ip_gre.c:776 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2f0/0x870 net/core/dev.c:3861 sch_direct_xmit+0x241/0x4b0 net/sched/sch_generic.c:347 __dev_xmit_skb net/core/dev.c:4152 [inline] __dev_queue_xmit+0x1826/0x3b70 net/core/dev.c:4729 __bond_start_xmit include/linux/netdevice.h:-1 [inline] bond_start_xmit+0xdc7/0x1a10 drivers/net/bonding/bond_main.c:5579 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2f0/0x870 net/core/dev.c:3861 __dev_queue_xmit+0x1b50/0x3b70 net/core/dev.c:4763 neigh_output include/net/neighbour.h:547 [inline] ip6_finish_output2+0x1162/0x14c0 net/ipv6/ip6_output.c:136 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245