INFO: task kworker/u8:26:22024 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u8:26 state:D stack:23160 pid:22024 tgid:22024 ppid:2 task_flags:0x4208060 flags:0x00080000 Workqueue: ipv6_addrconf addrconf_dad_work Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x14ef/0x4fb0 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0x164/0x360 kernel/sched/core.c:6960 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017 __mutex_lock_common kernel/locking/mutex.c:692 [inline] __mutex_lock+0x7fe/0x1300 kernel/locking/mutex.c:776 rtnl_net_lock include/linux/rtnetlink.h:130 [inline] addrconf_dad_work+0x11e/0x14c0 net/ipv6/addrconf.c:4194 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340 worker_thread+0x89f/0xd90 kernel/workqueue.c:3421 kthread+0x726/0x8b0 kernel/kthread.c:463 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Showing all locks held in the system: 1 lock held by pool_workqueue_/3: #0: ffffffff8e360c38 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:311 [inline] #0: ffffffff8e360c38 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2d0/0x770 kernel/rcu/tree_exp.h:956 1 lock held by khungtaskd/31: #0: ffffffff8e35a320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #0: ffffffff8e35a320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #0: ffffffff8e35a320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775 2 locks held by getty/5584: #0: ffff88802fffc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13c0 drivers/tty/n_tty.c:2211 2 locks held by syz-executor/5812: 3 locks held by kworker/1:3/5827: #0: ffff88813fe16948 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88813fe16948 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc9000403fbc0 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc9000403fbc0 ((reg_check_chans).work){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: reg_check_chans_work+0xa5/0xf40 net/wireless/reg.c:2453 3 locks held by kworker/0:4/5903: #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc9000458fbc0 (deferred_process_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc9000458fbc0 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104 3 locks held by kworker/0:6/5918: #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc9000461fbc0 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc9000461fbc0 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8fb20f28 (ovs_mutex){+.+.}-{4:4}, at: ovs_lock net/openvswitch/datapath.c:108 [inline] #2: ffffffff8fb20f28 (ovs_mutex){+.+.}-{4:4}, at: ovs_dp_masks_rebalance+0x2f/0xe0 net/openvswitch/datapath.c:2561 3 locks held by kworker/1:6/5940: 5 locks held by kworker/1:7/5951: 4 locks held by kworker/1:10/10166: 2 locks held by kworker/1:11/10167: 3 locks held by kworker/0:12/12535: #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88813fe15948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc900041cfbc0 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc900041cfbc0 ((work_completion)(&(&ovs_net->masks_rebalance)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8fb20f28 (ovs_mutex){+.+.}-{4:4}, at: ovs_lock net/openvswitch/datapath.c:108 [inline] #2: ffffffff8fb20f28 (ovs_mutex){+.+.}-{4:4}, at: ovs_dp_masks_rebalance+0x2f/0xe0 net/openvswitch/datapath.c:2561 3 locks held by kworker/u8:26/22024: #0: ffff88802fe3e148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88802fe3e148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc900110dfbc0 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc900110dfbc0 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] #2: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x11e/0x14c0 net/ipv6/addrconf.c:4194 5 locks held by kworker/u8:39/22039: #0: ffff88801b29f148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88801b29f148 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0 kernel/workqueue.c:3340 #1: ffffc90011297bc0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc90011297bc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0 kernel/workqueue.c:3340 #2: ffffffff8f799d50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xfe/0x7b0 net/core/net_namespace.c:670 #3: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline] #3: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x2a4/0x940 net/core/net_namespace.c:248 #4: ffffffff8e360c38 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline] #4: ffffffff8e360c38 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770 kernel/rcu/tree_exp.h:956 1 lock held by syz-executor/30027: #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline] #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 drivers/net/tun.c:3436 1 lock held by syz-executor/32145: #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline] #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 drivers/net/tun.c:3436 1 lock held by syz-executor/32148: #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline] #0: ffffffff8f7a86c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 drivers/net/tun.c:3436 1 lock held by syz.8.8465/3405: 2 locks held by syz-executor/3446: 2 locks held by syz-executor/3453: 2 locks held by syz-executor/3454: 3 locks held by syz-executor/3456: ============================================= NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 Call Trace: 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:160 [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:346 [inline] watchdog+0xf90/0xfe0 kernel/hung_task.c:515 kthread+0x726/0x8b0 kernel/kthread.c:463 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 22039 Comm: kworker/u8:39 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 Workqueue: netns cleanup_net RIP: 0010:__this_cpu_preempt_check+0x0/0x20 lib/smp_processor_id.c:63 Code: 39 e7 8b e8 b2 6e af f5 e8 1d c9 ba f5 eb aa 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 0f 1e fa 48 89 fe 48 c7 c7 80 38 e7 8b e9 fd fe ff ff cc cc cc RSP: 0018:ffffc90000a07b88 EFLAGS: 00000002 RAX: 0000000000000000 RBX: 0000000000000202 RCX: 0000000080000101 RDX: ffffc90000a07d01 RSI: ffffffff8be73860 RDI: ffffffff8daf01d0 RBP: dffffc0000000000 R08: ffffc90000a08950 R09: 0000000000000000 R10: ffffc90000a07d18 R11: fffff52000140fa5 R12: ffffc90000a08960 R13: ffffffff8174c0e5 R14: ffffffff8e35a320 R15: ffff888068c4db80 FS: 0000000000000000(0000) GS:ffff888125a2a000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffcebb24ff0 CR3: 000000008b33e000 CR4: 00000000003526f0 Call Trace: lockdep_recursion_inc kernel/locking/lockdep.c:465 [inline] lock_release+0xa1/0x3a0 kernel/locking/lockdep.c:5888 rcu_lock_release include/linux/rcupdate.h:341 [inline] rcu_read_unlock include/linux/rcupdate.h:897 [inline] class_rcu_destructor include/linux/rcupdate.h:1195 [inline] unwind_next_frame+0x1aaa/0x23c0 arch/x86/kernel/unwind_orc.c:695 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4953 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x370/0x6e0 mm/slub.c:5270 skb_ext_maybe_cow net/core/skbuff.c:7044 [inline] skb_ext_add+0x1b6/0x8f0 net/core/skbuff.c:7119 nf_bridge_unshare net/bridge/br_netfilter_hooks.c:169 [inline] br_nf_forward_ip+0xc6/0x7e0 net/bridge/br_netfilter_hooks.c:681 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline] nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623 nf_hook include/linux/netfilter.h:273 [inline] NF_HOOK+0x23e/0x3f0 include/linux/netfilter.h:316 __br_forward+0x397/0x540 net/bridge/br_forward.c:115 br_handle_frame_finish+0x1492/0x1b40 net/bridge/br_input.c:229 br_nf_hook_thresh+0x3dd/0x4c0 net/bridge/br_netfilter_hooks.c:-1 br_nf_pre_routing_finish_ipv6+0xa3a/0xd70 net/bridge/br_netfilter_ipv6.c:-1 NF_HOOK include/linux/netfilter.h:318 [inline] br_nf_pre_routing_ipv6+0x374/0x6f0 net/bridge/br_netfilter_ipv6.c:184 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline] nf_hook_bridge_pre net/bridge/br_input.c:291 [inline] br_handle_frame+0x989/0x1520 net/bridge/br_input.c:442 __netif_receive_skb_core+0x98f/0x30a0 net/core/dev.c:6039 __netif_receive_skb_one_core net/core/dev.c:6150 [inline] __netif_receive_skb+0x72/0x370 net/core/dev.c:6265 process_backlog+0x54e/0x1340 net/core/dev.c:6617 __napi_poll+0xae/0x320 net/core/dev.c:7681 napi_poll net/core/dev.c:7744 [inline] net_rx_action+0x696/0xe30 net/core/dev.c:7896 handle_softirqs+0x22a/0x7c0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:lock_acquire+0x221/0x330 kernel/locking/lockdep.c:5872 Code: ff ff ff e8 51 03 d9 09 f7 44 24 08 00 02 00 00 0f 84 3a ff ff ff 65 48 8b 05 3b 44 30 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 08 ff 32 RSP: 0018:ffffc90011297258 EFLAGS: 00000282 RAX: 0c4521d8ebb8de00 RBX: 0000000000000000 RCX: 0000000000000046 RDX: 00000000b8017dcb RSI: ffffffff8dd3c3f0 RDI: ffffffff8be73880 RBP: ffffffff8174c0e5 R08: ffffffff8174c0e5 R09: ffffffff8e35a320 R10: ffffc900112973b8 R11: ffffffff81ae4560 R12: 0000000000000002 R13: ffffffff8e35a320 R14: 0000000000000000 R15: 0000000000000246 rcu_lock_acquire include/linux/rcupdate.h:331 [inline] rcu_read_lock include/linux/rcupdate.h:867 [inline] class_rcu_constructor include/linux/rcupdate.h:1195 [inline] unwind_next_frame+0xc2/0x23c0 arch/x86/kernel/unwind_orc.c:495 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free mm/slub.c:6670 [inline] kfree+0x1be/0x650 mm/slub.c:6878 free_netdev+0x12f/0x6d0 net/core/dev.c:12163 netdev_run_todo+0xc55/0xde0 net/core/dev.c:11708 ops_exit_rtnl_list net/core/net_namespace.c:189 [inline] ops_undo_list+0x3d8/0x940 net/core/net_namespace.c:248 cleanup_net+0x4df/0x7b0 net/core/net_namespace.c:696 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xaec/0x17a0 kernel/workqueue.c:3340 worker_thread+0x89f/0xd90 kernel/workqueue.c:3421 kthread+0x726/0x8b0 kernel/kthread.c:463 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246