INFO: task syz-executor:24888 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:23160 pid:24888 tgid:24888 ppid:1      task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5504 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7228
 __schedule_loop kernel/sched/core.c:7307 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7322
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7379
 __mutex_lock_common kernel/locking/mutex.c:726 [inline]
 __mutex_lock+0x7bf/0x1550 kernel/locking/mutex.c:821
 del_device_store+0xd6/0x370 drivers/net/netdevsim/bus.c:234
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd602b5d68e
RSP: 002b:00007ffd0943f728 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000555575e4c500 RCX: 00007fd602b5d68e
RDX: 0000000000000001 RSI: 00007ffd0943f7b0 RDI: 0000000000000005
RBP: 00007fd602c336f2 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd0943f7b0 R14: 00007fd603944620 R15: 0000000000000003
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 25348 Comm: kworker/1:22 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events_power_efficient neigh_periodic_work
RIP: 0010:__preempt_count_add kernel/rcu/tree.c:748 [inline]
RIP: 0010:rcu_is_watching+0x6/0xb0 kernel/rcu/tree.c:751
Code: e8 2f 1a 44 03 eb cc 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 <41> 56 53 65 ff 05 40 56 8f 11 e8 fb 17 fd 09 89 c3 83 f8 08 73 65
RSP: 0018:ffffc90000a07aa8 EFLAGS: 00000097
RAX: 0000000000000001 RBX: ffffffff8547e139 RCX: ffff888042c29f00
RDX: 0000000000000100 RSI: ffffffff8547e139 RDI: ffff8880b8736b10
RBP: ffffc90000a07c50 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff20622df R12: 0000000000000005
R13: ffffffff8547e139 R14: ffff8880b8736b10 R15: 0000000000000200
FS:  0000000000000000(0000) GS:ffff88812537c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd40714d30 CR3: 000000000e746000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 trace_lock_release include/trace/events/lock.h:68 [inline]
 lock_release+0x4b/0x3c0 kernel/locking/lockdep.c:5879
 local_lock_release include/linux/local_lock_internal.h:62 [inline]
 get_random_u16+0x45c/0x910 drivers/char/random.c:540
 cake_get_flow_quantum+0x18e/0x290 net/sched/sch_cake.c:706
 cake_dequeue+0x2e47/0x4f10 net/sched/sch_cake.c:2176
 dequeue_skb net/sched/sch_generic.c:322 [inline]
 qdisc_restart net/sched/sch_generic.c:427 [inline]
 __qdisc_run+0x24c/0x1620 net/sched/sch_generic.c:445
 qdisc_run include/net/pkt_sched.h:120 [inline]
 __dev_xmit_skb net/core/dev.c:4294 [inline]
 __dev_queue_xmit+0x1c00/0x37f0 net/core/dev.c:4833
 dev_queue_xmit include/linux/netdevice.h:3436 [inline]
 neigh_hh_output include/net/neighbour.h:544 [inline]
 neigh_output include/net/neighbour.h:558 [inline]
 ip_finish_output2+0xbda/0x10b0 net/ipv4/ip_output.c:236
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip_output+0x29f/0x450 net/ipv4/ip_output.c:437
 synproxy_send_client_synack+0x89b/0xde0 net/netfilter/nf_synproxy_core.c:487
 nft_synproxy_eval_v4+0x37b/0x530 net/netfilter/nft_synproxy.c:60
 nft_synproxy_do_eval+0x335/0x550 net/netfilter/nft_synproxy.c:142
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 nft_do_chain+0x48d/0x1b10 net/netfilter/nf_tables_core.c:285
 nft_do_chain_inet+0x360/0x4b0 net/netfilter/nft_chain_filter.c:162
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x21f/0x3c0 include/linux/netfilter.h:316
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 __netif_receive_skb_one_core net/core/dev.c:6206 [inline]
 __netif_receive_skb net/core/dev.c:6319 [inline]
 process_backlog+0xa34/0x1860 net/core/dev.c:6670
 __napi_poll+0xaa/0x330 net/core/dev.c:7729
 napi_poll net/core/dev.c:7792 [inline]
 net_rx_action+0x61d/0xf50 net/core/dev.c:7949
 handle_softirqs+0x225/0x840 kernel/softirq.c:622
 do_softirq+0x76/0xd0 kernel/softirq.c:523
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 neigh_periodic_work+0xc23/0xe40 net/core/neighbour.c:1035
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>