INFO: task hung in hci_cmd_sync_clear (2)

Status: upstream: reported syz repro on 2025/01/26 06:48
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+bb555a2060a46486fa24@syzkaller.appspotmail.com
First crash: 579d, last: 12d
Fix bisection: failed (error log, bisect log)
  
Bug presence (2)
Date Name Commit Repro Result
2025/03/11 linux-6.1.y (ToT) 6ae7ac5c4251 syz [report] INFO: task hung in hci_cmd_sync_clear
2025/03/10 upstream (ToT) 4d872d51bc9d syz Didn't crash
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in hci_cmd_sync_clear bluetooth 1 4 1471d 1618d 0/29 auto-obsoleted due to no activity on 2022/11/16 14:10
linux-6.1 INFO: task hung in hci_cmd_sync_clear 1 1 895d 895d 0/3 auto-obsoleted due to no activity on 2024/06/24 21:55
upstream INFO: task hung in hci_cmd_sync_clear (2) bluetooth 1 15 886d 1292d 0/29 auto-obsoleted due to no activity on 2024/06/23 16:01
upstream INFO: task hung in hci_cmd_sync_clear (3) prio:high kernel 1 syz done 118 21h20m 657d 0/29 upstream: reported syz repro on 2024/11/09 06:00
Fix bisection attempts (2)
Created Duration User Patch Repo Result
2025/11/06 12:49 1h52m fix candidate upstream OK (0) job log
2025/06/27 09:52 17m bisect fix linux-6.1.y error job log

Sample crash report:
INFO: task syz-executor:4453 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:0     pid:4453  ppid:1      flags:0x0000000d
Call trace:
 __switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5246 [inline]
 __schedule+0xdb4/0x1a6c kernel/sched/core.c:6563
 schedule+0xc4/0x170 kernel/sched/core.c:6639
 schedule_timeout+0xc8/0x2f4 kernel/time/timer.c:2144
 do_wait_for_common+0x28c/0x3ec kernel/sched/completion.c:85
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x44/0x5c kernel/sched/completion.c:138
 __flush_work+0x140/0x1ec kernel/workqueue.c:3076
 __cancel_work_timer+0x2f8/0x450 kernel/workqueue.c:3163
 cancel_work_sync+0x24/0x38 kernel/workqueue.c:3199
 hci_cmd_sync_clear+0x38/0x1e8 net/bluetooth/hci_sync.c:674
 hci_unregister_dev+0x190/0x4d4 net/bluetooth/hci_core.c:2729
 vhci_release+0x7c/0xcc drivers/bluetooth/hci_vhci.c:573
 __fput+0x1b4/0x7b0 fs/file_table.c:320
 ____fput+0x20/0x30 fs/file_table.c:348
 task_work_run+0x1f4/0x280 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0x54c/0x19ac kernel/exit.c:887
 do_group_exit+0x198/0x238 kernel/exit.c:1030
 get_signal+0x11f4/0x133c kernel/signal.c:2880
 do_signal arch/arm64/kernel/signal.c:1095 [inline]
 do_notify_resume+0x364/0x2c84 arch/arm64/kernel/signal.c:1148
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Showing all locks held in the system:
3 locks held by kworker/u4:1/11:
 #0: ffff0000c0029138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff80001cb57c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
1 lock held by rcu_tasks_kthre/12:
 #0: ffff800015557db0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffff8000155585d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffff800015557440 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:349
3 locks held by kworker/u5:0/48:
 #0: ffff0000cc7f6138 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff80001f077c40 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff0000cb2854b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x180/0x32c net/bluetooth/hci_sync.c:327
3 locks held by kworker/1:2/111:
 #0: ffff0000d39c7538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800020707c40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
2 locks held by getty/4085:
 #0: ffff0000d6e5d098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80001fa162f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x2e8/0xfa8 drivers/tty/n_tty.c:2198
3 locks held by kworker/0:2/4372:
 #0: ffff0000c0020938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800020a67c40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff0000f05e0240 (&data->fib_lock){+.+.}-{3:3}, at: nsim_fib_event_work+0x1d8/0x2708 drivers/net/netdevsim/fib.c:1491
3 locks held by kworker/0:3/4387:
 #0: ffff0000c0020938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800020b17c40 (deferred_process_work){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
3 locks held by kworker/0:20/4587:
 #0: ffff0000d39c7538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff8000214b7c40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
4 locks held by kworker/u4:6/5957:
 #0: ffff0000c0845138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800025217c40 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
 #2: ffff8000179f85d0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x144/0xa90 net/core/net_namespace.c:594
 #3: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
1 lock held by syz.0.7900/12628:

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Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/16 14:37 linux-6.1.y e4f7d8be268e 746171ee .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in hci_cmd_sync_clear
2026/07/19 01:34 linux-6.1.y 090666d3cc90 72524a66 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in hci_cmd_sync_clear
2026/01/01 11:10 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in hci_cmd_sync_clear
2025/12/30 02:11 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in hci_cmd_sync_clear
2025/01/26 06:47 linux-6.1.y 75cefdf153f5 9fbd772e .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in hci_cmd_sync_clear
* Struck through repros no longer work on HEAD.