BUG: workqueue lockup in reg_todo

Status: moderation: reported on 2026/09/15 07:40
Subsystems: wireless
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+59d9c0001a31dba6501d@syzkaller.appspotmail.com
First crash: 4d00h, last: 3d22h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
65f122f3 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ BUG: workqueue lockup in reg_todo 2026/09/13 00:01 2026/09/13 00:01 2026/09/13 00:07 70a60e12

Sample crash report:
BUG: workqueue lockup - pool cpus=0 node=0 flags=0x0 nice=0 stuck for 48s!
Showing busy workqueues and worker pools:
workqueue events: flags=0x100
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=14 refcnt=15
    in-flight: 4378:reg_todo for 48s
    pending: psi_avgs_work, vmstat_shepherd, 2*psi_avgs_work, 4*ovs_dp_masks_rebalance, 2*nsim_dev_hwstats_traffic_work, free_obj_work, psi_avgs_work, delayed_vfree_work
  pwq 6: cpus=1 node=0 flags=0x0 nice=0 active=5 refcnt=6
    pending: 4*nsim_dev_hwstats_traffic_work, psi_avgs_work
workqueue events_unbound: flags=0x2
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=9 refcnt=10
    in-flight: 42:cfg80211_wiphy_work for 80s cfg80211_wiphy_work ,4962:cfg80211_wiphy_work for 82s cfg80211_wiphy_work ,40:cfg80211_wiphy_work for 67s cfg80211_wiphy_work ,63:cfg80211_wiphy_work for 89s cfg80211_wiphy_work
    pending: macvlan_process_broadcast
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=15 refcnt=16
    in-flight: 12:cfg80211_wiphy_work for 49s cfg80211_wiphy_work ,61:cfg80211_wiphy_work for 85s cfg80211_wiphy_work ,1106:cfg80211_wiphy_work for 37s
    pending: nsim_dev_trap_report_work, toggle_allocation_gate, 2*nsim_dev_trap_report_work, flush_memcg_stats_dwork, 2*nsim_dev_trap_report_work, cfg80211_wiphy_work, nsim_dev_trap_report_work, cfg80211_wiphy_work
workqueue events_power_efficient: flags=0x82
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: crda_timeout_work
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=8 refcnt=9
    in-flight: 13:neigh_periodic_work for 24s ,5993:reg_check_chans_work for 15s
    pending: wg_ratelimiter_gc_entries, 2*neigh_managed_work, neigh_periodic_work, gc_worker, do_cache_clean
workqueue events_dfl_long: flags=0x2
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=6 refcnt=7
    pending: 6*defense_work_handler
workqueue mm_percpu_wq: flags=0x108
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: vmstat_update
  pwq 6: cpus=1 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: vmstat_update
workqueue writeback: flags=0x4a
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    in-flight: 1183:wb_workfn for 87s
workqueue bat_events: flags=0x6000a
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=43 MAYDAY
    in-flight: 2852(RESCUER):batadv_tt_purge for 9s
    pending: mayday_cursor_func
    inactive: batadv_tt_purge, 2*batadv_dat_purge, 2*batadv_bla_periodic_work, batadv_dat_purge, batadv_bla_periodic_work, batadv_dat_purge, batadv_bla_periodic_work, batadv_iv_send_outstanding_bat_ogm_packet, 5*batadv_mcast_mla_update, 5*batadv_iv_send_outstanding_bat_ogm_packet, 5*batadv_purge_orig, 7*batadv_iv_send_outstanding_bat_ogm_packet, batadv_tt_purge, batadv_bla_periodic_work, batadv_dat_purge, 2*batadv_tt_purge
workqueue ext4-rsv-conversion: flags=0xa
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=4 MAYDAY
    in-flight: 4303(RESCUER):ext4_end_io_rsv_work for 8s
    pending: mayday_cursor_func
workqueue wg-crypt-wg0: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=4 refcnt=5
    in-flight: 4801:wg_packet_tx_worker for 91s wg_packet_tx_worker
    pending: wg_packet_encrypt_worker, wg_packet_decrypt_worker
workqueue wg-kex-wg1: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg1: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker, wg_packet_decrypt_worker
workqueue wg-kex-wg0: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-kex-wg0: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg0: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker, wg_packet_decrypt_worker
workqueue wg-kex-wg2: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-crypt-wg2: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    in-flight: 9:wg_packet_decrypt_worker for 83s
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg1: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-kex-wg1: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg1: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_tx_worker, wg_packet_encrypt_worker, wg_packet_decrypt_worker
workqueue wg-kex-wg2: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-crypt-wg2: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg0: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg0: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg1: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg1: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-crypt-wg2: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg0: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg0: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker, wg_packet_decrypt_worker
workqueue wg-kex-wg1: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-crypt-wg1: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_decrypt_worker, wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg2: flags=0x124
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_receive_worker
workqueue wg-kex-wg2: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg2: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_encrypt_worker, wg_packet_tx_worker
workqueue wg-kex-wg0: flags=0x6
  pwq 8: cpus=0-1 flags=0x6 nice=0 active=1 refcnt=2
    pending: wg_packet_handshake_send_worker
workqueue wg-crypt-wg0: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_tx_worker, wg_packet_decrypt_worker, wg_packet_encrypt_worker
workqueue wg-crypt-wg1: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=3 refcnt=4
    pending: wg_packet_tx_worker, wg_packet_decrypt_worker, wg_packet_encrypt_worker
workqueue wg-crypt-wg2: flags=0x128
  pwq 2: cpus=0 node=0 flags=0x0 nice=0 active=2 refcnt=3
    pending: wg_packet_tx_worker, wg_packet_encrypt_worker
pool 2: cpus=0 node=0 flags=0x0 nice=0 hung=48s workers=8 idle: 866 4818 4794 10 4793
pool 8: cpus=0-1 flags=0x6 nice=0 hung=8s workers=11 manager: 5994
Showing backtraces of busy workers in stalled worker pools:
pool 2:
task:kworker/0:3     state:R  running task     stack:0     pid:4378  tgid:4378  ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: events reg_todo
Call trace:
 __switch_to+0x2b4/0x6e4 arch/arm64/kernel/process.c:775 (T)
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x1370/0x2d80 kernel/sched/core.c:7270
 preempt_schedule_common+0xd4/0x190 kernel/sched/core.c:7449
 preempt_schedule+0x60/0x78 kernel/sched/core.c:7473
 __local_bh_enable_ip+0x20c/0x35c kernel/softirq.c:480
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:237 [inline]
 _raw_spin_unlock_bh+0x3c/0x4c kernel/locking/spinlock.c:245
 spin_unlock_bh include/linux/spinlock.h:407 [inline]
 reg_process_pending_beacon_hints net/wireless/reg.c:3146 [inline]
 reg_todo+0x608/0x6a4 net/wireless/reg.c:3207
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3470
 worker_thread+0x798/0xbd0 kernel/workqueue.c:3551
 kthread+0x304/0x3d4 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838
pool 2:
task:kworker/0:0     state:R  running task     stack:0     pid:9     tgid:9     ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: wg-crypt-wg2 wg_packet_decrypt_worker
Call trace:
 __switch_to+0x2b4/0x6e4 arch/arm64/kernel/process.c:775 (T)
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x1370/0x2d80 kernel/sched/core.c:7270
 preempt_schedule_common+0xd4/0x190 kernel/sched/core.c:7449
 preempt_schedule+0x60/0x78 kernel/sched/core.c:7473
 __local_bh_enable_ip+0x20c/0x35c kernel/softirq.c:480
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:237 [inline]
 _raw_spin_unlock_bh+0x3c/0x4c kernel/locking/spinlock.c:245
 spin_unlock_bh include/linux/spinlock.h:407 [inline]
 ptr_ring_consume_bh include/linux/ptr_ring.h:399 [inline]
 wg_packet_decrypt_worker+0x254/0xa00 drivers/net/wireguard/receive.c:499
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3470
 worker_thread+0x798/0xbd0 kernel/workqueue.c:3551
 kthread+0x304/0x3d4 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838
pool 2:
task:kworker/0:6     state:R  running task     stack:0     pid:4801  tgid:4801  ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: wg-crypt-wg0 wg_packet_tx_worker
Call trace:
 __switch_to+0x2b4/0x6e4 arch/arm64/kernel/process.c:775 (T)
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x1370/0x2d80 kernel/sched/core.c:7270
 preempt_schedule_common+0xd4/0x190 kernel/sched/core.c:7449
 preempt_schedule+0x60/0x78 kernel/sched/core.c:7473
 __local_bh_enable_ip+0x20c/0x35c kernel/softirq.c:480
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:923 [inline]
 mod_peer_timer+0x21c/0x25c drivers/net/wireguard/timers.c:38
 wg_timers_any_authenticated_packet_traversal+0x98/0xc0 drivers/net/wireguard/timers.c:218
 wg_packet_create_data_done drivers/net/wireguard/send.c:247 [inline]
 wg_packet_tx_worker+0x130/0x75c drivers/net/wireguard/send.c:276
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3470
 worker_thread+0x798/0xbd0 kernel/workqueue.c:3551
 kthread+0x304/0x3d4 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:838

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/11 09:36 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 5445d6419962 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: workqueue lockup in reg_todo
2026/09/11 07:38 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 5445d6419962 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: workqueue lockup in reg_todo
* Struck through repros no longer work on HEAD.