syzbot


INFO: task hung in hub_event (4)

Status: upstream: reported on 2025/10/27 21:24
Reported-by: syzbot+f5ff5c7164a0f46a848c@syzkaller.appspotmail.com
First crash: 75d, last: 42d
Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in hub_event usb 1 19 2290d 2466d 0/29 auto-closed as invalid on 2020/01/02 20:34
linux-6.6 INFO: task hung in hub_event 1 1 75d 75d 0/2 upstream: reported on 2025/10/27 22:05
linux-4.14 INFO: task hung in hub_event 1 5 1462d 1484d 0/1 auto-closed as invalid on 2022/05/10 10:19
linux-5.15 INFO: task hung in hub_event (4) 1 3 262d 276d 0/3 auto-obsoleted due to no activity on 2025/08/02 17:03
linux-6.1 INFO: task hung in hub_event (2) 1 1 844d 844d 0/3 auto-obsoleted due to no activity on 2023/12/29 05:51
upstream INFO: task hung in hub_event (2) usb 1 27 1461d 1506d 0/29 closed as invalid on 2022/02/08 09:40
linux-5.15 INFO: task hung in hub_event (2) 1 1 750d 750d 0/3 auto-obsoleted due to no activity on 2024/04/01 17:35
upstream INFO: task hung in hub_event (3) usb 1 722 1d05h 1092d 0/29 upstream: reported on 2023/01/14 20:19
linux-6.1 INFO: task hung in hub_event (3) 1 8 279d 282d 0/3 auto-obsoleted due to no activity on 2025/07/16 18:44
linux-5.15 INFO: task hung in hub_event (3) 1 1 539d 539d 0/3 auto-obsoleted due to no activity on 2024/10/29 18:51
linux-5.15 INFO: task hung in hub_event 1 3 861d 1025d 0/3 auto-obsoleted due to no activity on 2023/12/12 00:26
linux-6.1 INFO: task hung in hub_event 1 2 1007d 1036d 0/3 auto-obsoleted due to no activity on 2023/08/08 09:24

Sample crash report:
INFO: task kworker/1:6:4339 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:6     state:D stack:21128 pid:4339  ppid:2      flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 device_lock include/linux/device.h:840 [inline]
 hub_event+0x1a7/0x54e0 drivers/usb/core/hub.c:5845
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 process_scheduled_works kernel/workqueue.c:2355 [inline]
 worker_thread+0xd62/0x1250 kernel/workqueue.c:2441
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
INFO: task udevd:8751 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:23584 pid:8751  ppid:3637   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 device_lock include/linux/device.h:840 [inline]
 uevent_show+0x16c/0x320 drivers/base/core.c:2669
 dev_attr_show+0x50/0xb0 drivers/base/core.c:2372
 sysfs_kf_seq_show+0x349/0x4b0 fs/sysfs/file.c:59
 seq_read_iter+0x49b/0xd50 fs/seq_file.c:230
 call_read_iter include/linux/fs.h:2259 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x434/0x920 fs/read_write.c:470
 ksys_read+0x143/0x240 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6c34ca7407
RSP: 002b:00007ffe0f638e50 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f6c35386880 RCX: 00007f6c34ca7407
RDX: 0000000000001000 RSI: 0000556d4ab04a00 RDI: 0000000000000008
RBP: 00007f6c34defff0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a
R13: 00007f6c34defea0 R14: 0000000000000000 R15: 0000556d4ab07f30
 </TASK>
INFO: task syz.7.914:9320 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.7.914       state:D stack:24000 pid:9320  ppid:7510   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x97/0x280 kernel/time/timer.c:2143
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x2b9/0x590 kernel/sched/completion.c:138
 i2c_del_adapter+0x5da/0x730 drivers/i2c/i2c-core-base.c:1816
 cp2112_remove+0x57/0x2a0 drivers/hid/hid-cp2112.c:1406
 hid_device_remove+0x21e/0x330 drivers/hid/hid-core.c:-1
 device_remove drivers/base/dd.c:548 [inline]
 __device_release_driver drivers/base/dd.c:1260 [inline]
 device_release_driver_internal+0x4be/0x850 drivers/base/dd.c:1286
 bus_remove_device+0x2e2/0x400 drivers/base/bus.c:531
 device_del+0x628/0xa70 drivers/base/core.c:3885
 hid_remove_device drivers/hid/hid-core.c:2842 [inline]
 hid_destroy_device+0x66/0x100 drivers/hid/hid-core.c:2861
 usbhid_disconnect+0x9b/0xc0 drivers/hid/usbhid/hid-core.c:1454
 usb_unbind_interface+0x1ee/0x860 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:550 [inline]
 __device_release_driver drivers/base/dd.c:1260 [inline]
 device_release_driver_internal+0x522/0x850 drivers/base/dd.c:1286
 bus_remove_device+0x2e2/0x400 drivers/base/bus.c:531
 device_del+0x628/0xa70 drivers/base/core.c:3885
 usb_disable_device+0x3e2/0x890 drivers/usb/core/message.c:1414
 usb_disconnect+0x348/0x8a0 drivers/usb/core/hub.c:2314
 hub_quiesce+0x171/0x330 drivers/usb/core/hub.c:1379
 hub_disconnect+0xc1/0x460 drivers/usb/core/hub.c:1785
 usb_unbind_interface+0x1ee/0x860 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:550 [inline]
 __device_release_driver drivers/base/dd.c:1260 [inline]
 device_release_driver_internal+0x522/0x850 drivers/base/dd.c:1286
 proc_disconnect_claim+0x2dd/0x350 drivers/usb/core/devio.c:2490
 usbdev_do_ioctl drivers/usb/core/devio.c:2773 [inline]
 usbdev_ioctl+0xf09/0x1e50 drivers/usb/core/devio.c:2817
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f24f1b8f749
RSP: 002b:00007f24f2a45038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f24f1de5fa0 RCX: 00007f24f1b8f749
RDX: 0000200000002600 RSI: 000000008108551b RDI: 0000000000000004
RBP: 00007f24f1c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f24f1de6038 R14: 00007f24f1de5fa0 R15: 00007fff20045a38
 </TASK>
INFO: task syz.7.914:9359 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.7.914       state:D stack:29184 pid:9359  ppid:7510   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 device_lock include/linux/device.h:840 [inline]
 usbdev_do_ioctl drivers/usb/core/devio.c:2609 [inline]
 usbdev_ioctl+0x143/0x1e50 drivers/usb/core/devio.c:2817
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f24f1b8f749
RSP: 002b:00007f24f2a24038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f24f1de6090 RCX: 00007f24f1b8f749
RDX: 0000200000000040 RSI: 0000000080045515 RDI: 0000000000000004
RBP: 00007f24f1c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f24f1de6128 R14: 00007f24f1de6090 R15: 00007fff20045a38
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8cb2b630 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8cb2be50 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/27:
 #0: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8cb2aca0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
2 locks held by getty/4025:
 #0: ffff8880300db098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
3 locks held by kworker/1:6/4339:
 #0: ffff888143e76138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90004907d00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #2: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: hub_event+0x1a7/0x54e0 drivers/usb/core/hub.c:5845
2 locks held by kworker/u4:9/4396:
 #0: ffff8880b8e3aad8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xa5/0x140 kernel/sched/core.c:545
 #1: ffff8880b8e27848 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x398/0x6d0 kernel/sched/psi.c:999
4 locks held by udevd/8751:
 #0: ffff8880781272f0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xad/0xd50 fs/seq_file.c:182
 #1: ffff88802459bc88 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x58/0x410 fs/kernfs/file.c:172
 #2: ffff88807a558e88 (kn->active#5){++++}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff88807a558e88 (kn->active#5){++++}-{0:0}, at: kernfs_seq_start+0xae/0x410 fs/kernfs/file.c:173
 #3: ffff888078408190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #3: ffff888078408190 (&dev->mutex){....}-{3:3}, at: uevent_show+0x16c/0x320 drivers/base/core.c:2669
5 locks held by syz.7.914/9320:
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_do_ioctl drivers/usb/core/devio.c:2609 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_ioctl+0x143/0x1e50 drivers/usb/core/devio.c:2817
 #1: ffff8881457da118 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #1: ffff8881457da118 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1080 [inline]
 #1: ffff8881457da118 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb2/0x850 drivers/base/dd.c:1283
 #2: ffff888078408190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #2: ffff888078408190 (&dev->mutex){....}-{3:3}, at: usb_disconnect+0x107/0x8a0 drivers/usb/core/hub.c:2305
 #3: ffff8880745df118 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #3: ffff8880745df118 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1080 [inline]
 #3: ffff8880745df118 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb2/0x850 drivers/base/dd.c:1283
 #4: ffff888057f81a20 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #4: ffff888057f81a20 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1080 [inline]
 #4: ffff888057f81a20 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb2/0x850 drivers/base/dd.c:1283
1 lock held by syz.7.914/9359:
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_do_ioctl drivers/usb/core/devio.c:2609 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_ioctl+0x143/0x1e50 drivers/usb/core/devio.c:2817
1 lock held by syz.0.998/9737:
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_open+0x16b/0x790 drivers/usb/core/devio.c:1052
1 lock held by syz.8.1320/11287:
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:840 [inline]
 #0: ffff8881457d9190 (&dev->mutex){....}-{3:3}, at: usbdev_open+0x16b/0x790 drivers/usb/core/devio.c:1052
1 lock held by syz.5.1426/11926:
 #0: ffffffff8cb30840 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x48/0x600 kernel/rcu/tree.c:4023
2 locks held by sed/11960:

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
 watchdog+0xeee/0xf30 kernel/hung_task.c:377
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4396 Comm: kworker/u4:9 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:unwind_next_frame+0x93/0x20b0 arch/x86/kernel/unwind_orc.c:-1
Code: 49 89 df 49 c1 ef 03 43 0f b6 04 37 84 c0 0f 85 a0 19 00 00 8b 03 85 c0 0f 84 79 18 00 00 48 89 6c 24 08 89 84 24 8c 00 00 00 <4c> 89 ac 24 98 00 00 00 4c 89 64 24 68 4c 89 7c 24 18 bf 01 00 00
RSP: 0018:ffffc90004b2f550 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffc90004b2f688 RCX: 0000000080000001
RDX: ffffc90004b2f718 RSI: dffffc0000000000 RDI: ffffc90004b2f688
RBP: ffffc90004b2f6d0 R08: ffffc90004b2f678 R09: ffffc90004b2f6d8
R10: fffff52000965edd R11: 1ffff92000965edb R12: ffffffff812ff4da
R13: ffffc90004b2f688 R14: dffffc0000000000 R15: 1ffff92000965ed1
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5a7c810c50 CR3: 00000000338b6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __unwind_start+0x5bb/0x740 arch/x86/kernel/unwind_orc.c:717
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xda/0x140 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6b/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 kmem_cache_alloc_node+0x14d/0x320 mm/slub.c:3404
 __alloc_skb+0xfc/0x7e0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1271 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
 nsim_dev_trap_report_work+0x28f/0xaf0 drivers/net/netdevsim/dev.c:851
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/30 11:30 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in hub_event
2025/10/27 21:41 linux-6.1.y 8e6e2188d949 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in hub_event
2025/10/27 21:31 linux-6.1.y 8e6e2188d949 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in hub_event
2025/10/27 21:24 linux-6.1.y 8e6e2188d949 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in hub_event
* Struck through repros no longer work on HEAD.