INFO: task hung in device_write

Status: upstream: reported on 2026/08/04 22:26
Reported-by: syzbot+73dc7e2e73d72df67cf6@syzkaller.appspotmail.com
First crash: 15d, last: 15d
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in device_write 1 1 15d 15d 0/3 upstream: reported on 2026/08/04 20:17

Sample crash report:
INFO: task syz.0.81:6428 blocked for more than 204 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.81        state:D stack:24496 pid:6428  ppid:5774   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2c6/0x5a0 kernel/sched/completion.c:148
 new_lockspace fs/dlm/lockspace.c:638 [inline]
 __dlm_new_lockspace+0x1dec/0x2360 fs/dlm/lockspace.c:693
 device_create_lockspace+0xc8/0x350 fs/dlm/user.c:430
 device_write+0x875/0xed0 fs/dlm/user.c:622
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb4afb9e019
RSP: 002b:00007fb4addf6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fb4afe25fa0 RCX: 00007fb4afb9e019
RDX: 0000000000000078 RSI: 0000200000000400 RDI: 0000000000000007
RBP: 00007fb4afc3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb4afe26038 R14: 00007fb4afe25fa0 R15: 00007ffd0aa8edd8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/28:
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
1 lock held by dhcpcd/5439:
 #0: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6481
2 locks held by getty/5533:
 #0: ffff888031ee90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
2 locks held by kworker/1:3/5763:
 #0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc900046ffd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc900046ffd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
3 locks held by kworker/0:4/5815:
 #0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc900048dfd00 (deferred_process_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc900048dfd00 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
3 locks held by kworker/u4:25/6173:
 #0: ffff888017c71938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff888017c71938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc90003507d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc90003507d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:286
5 locks held by kworker/u4:28/6176:
 #0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc90003537d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc90003537d00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffffffff8e3ca0d0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x14c/0xbb0 net/core/net_namespace.c:606
 #3: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: default_device_exit_batch+0xf2/0xa00 net/core/dev.c:11732
 #4: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
 #4: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x306/0x880 kernel/rcu/tree_exp.h:1004
1 lock held by syz.0.81/6428:
 #0: ffffffff973c9a68 (&ls_lock){+.+.}-{3:3}, at: __dlm_new_lockspace+0xb1/0x2360 fs/dlm/lockspace.c:687
1 lock held by dlm_recoverd/6435:
 #0: ffff88802560aaa8 (&ls->ls_in_recovery){+.+.}-{3:3}, at: dlm_recoverd+0xa5/0x1e50 fs/dlm/recoverd.c:310
4 locks held by syz-executor/8474:
 #0: ffff8880210ba418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #1: ffff88803022dc88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
 #3: ffffffff8dcb7788 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd7/0x370 drivers/net/netdevsim/bus.c:209
4 locks held by syz-executor/8475:
 #0: ffff8880210ba418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #1: ffff88802c394888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
 #3: ffffffff8dcb7788 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd7/0x370 drivers/net/netdevsim/bus.c:209
4 locks held by syz-executor/8481:
 #0: ffff8880210ba418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #1: ffff88802ca49888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
 #3: ffffffff8dcb7788 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd7/0x370 drivers/net/netdevsim/bus.c:209
7 locks held by syz-executor/8485:
 #0: ffff8880210ba418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #1: ffff88805e622888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888024c70008 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
 #3: ffffffff8dcb7788 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd7/0x370 drivers/net/netdevsim/bus.c:209
 #4: ffff88804c7b6130 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1094 [inline]
 #4: ffff88804c7b6130 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1174 [inline]
 #4: ffff88804c7b6130 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xa7/0x6f0 drivers/base/dd.c:1371
 #5: ffff88804c7b7250 (&devlink->lock_key#10){+.+.}-{3:3}, at: nsim_drv_remove+0x50/0x170 drivers/net/netdevsim/dev.c:1676
 #6: ffffffff8e3d70c8 (rtnl_mutex){+.+.}-{3:3}, at: unregister_netdevice_notifier_net+0x88/0x2e0 net/core/dev.c:1960

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf59/0xfa0 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6189 Comm: kworker/u4:41 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:__lock_acquire+0x429/0x7d80 kernel/locking/lockdep.c:-1
Code: e8 00 00 00 42 80 3c 00 00 74 12 4c 89 ef e8 0e 66 77 00 49 b8 00 00 00 00 00 fc ff df 4c 89 6c 24 70 4c 89 bc 24 b0 00 00 00 <48> 8b 84 24 90 00 00 00 48 89 43 10 4c 8d 6b 18 4c 89 e8 48 c1 e8
RSP: 0018:ffffc900036173a0 EFLAGS: 00000046
RAX: 1ffff11005dad17c RBX: ffff88802ed68bd0 RCX: ffff88802ed68000
RDX: 0000000000000034 RSI: 0000000000000034 RDI: ffff88802ed68bd8
RBP: ffffc900036175e8 R08: dffffc0000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1d18f5e R12: 0000000000000000
R13: ffff88802ed68be0 R14: 0000000000000000 R15: ffff88802ed68ae0
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055ba9f3ce138 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 __pte_offset_map_lock+0x106/0x1d0 mm/pgtable-generic.c:375
 get_locked_pte include/linux/mm.h:2741 [inline]
 __text_poke+0x2a4/0xb40 arch/x86/kernel/alternative.c:2036
 text_poke arch/x86/kernel/alternative.c:2121 [inline]
 text_poke_bp_batch+0x7b3/0x980 arch/x86/kernel/alternative.c:2510
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_disable_cpuslocked+0xc5/0x1a0 kernel/jump_label.c:237
 static_key_disable+0x1a/0x20 kernel/jump_label.c:245
 toggle_allocation_gate+0x1cc/0x260 mm/kfence/core.c:852
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/04 22:35 linux-6.6.y aa0e49877a2e d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in device_write
2026/08/04 22:25 linux-6.6.y aa0e49877a2e d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in device_write
* Struck through repros no longer work on HEAD.