syzbot


INFO: task hung in pick_next_task_fair

Status: auto-obsoleted due to no activity on 2026/05/30 21:30
Subsystems: net
Labels: prio:high
[Documentation on labels]
First crash: 115d, last: 115d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
38ed327d-7bd9-4e67-8f19-d63ff5f65b3e assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ INFO: task hung in pick_next_task_fair 2026/05/25 22:43 2026/05/25 22:43 2026/05/25 22:56 c69befb30ac10e158cc9d1557b508ee3f0eca1de

			
		

Sample crash report:
INFO: task kworker/0:5:5317 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:5     state:D
  running task    
 stack:22696 pid:5317  tgid:5317  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0xeb1/0x41f0 kernel/sched/core.c:6907
 pick_next_task_fair+0x12b0/0x1fe0 kernel/sched/fair.c:8959
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/1:0/23:
4 locks held by kworker/1:1/28:
1 lock held by khungtaskd/30:
 #0: ffffffff896e05a0
 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
5 locks held by kworker/u8:7/336:
 #0: 
ffff888101299148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
 #1: ffffc90001c7fd18 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
 #2: ffffffff8aae0830 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x9e0 net/core/net_namespace.c:675
 #3: ffffffff8aaf8e68 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #3: ffffffff8aaf8e68 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
 #4: ffffffff896ec1b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311
4 locks held by kworker/1:2/923:
3 locks held by kworker/1:3/2813:
 #0: 
ffff88810006a148
 ((wq_completion)events_power_efficient
){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
 #1: ffffc9000555fd18 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
 #2: ffffffff8aaf8e68 (rtnl_mutex){+.+.}-{4:4}, at: reg_check_chans_work+0x91/0x11d0 net/wireless/reg.c:2462
1 lock held by udevd/2853:
 #0: ffff888101298188 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185
2 locks held by getty/2918:
 #0: 
ffff8881157a90a0
 (
&tty->ldisc_sem
){++++}-{0:0}
, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: 
ffffc900000432f0
 (
&ldata->atomic_read_lock
){+.+.}-{4:4}
, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
1 lock held by udevd/5215:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185
1 lock held by udevd/5226:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185
2 locks held by kworker/1:5/5227:
4 locks held by kworker/0:5/5317:
 #0: 
ffff88810006b548
 (
(wq_completion)events
){+.+.}-{0:0}
, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
 #1: 
ffffc9000302fd18
 (
kernfs_notify_work
){+.+.}-{0:0}
, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
 #2: 
ffff8881012982b8
 (
&root->kernfs_supers_rwsem
){++++}-{4:4}
, at: kernfs_notify_workfn+0xf7/0x5f0 fs/kernfs/file.c:932
 #3: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_notify_workfn+0xff/0x5f0 fs/kernfs/file.c:933
3 locks held by kworker/1:6/5507:
1 lock held by syz.0.274/6369:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_remove_by_name_ns+0x3d/0xf0 fs/kernfs/dir.c:1717
1 lock held by syz.3.277/6389:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_remove_by_name_ns+0x3d/0xf0 fs/kernfs/dir.c:1717
2 locks held by syz-executor/6395:
 #0: 
ffffffff8aae0830
 (
pernet_ops_rwsem
){++++}-{4:4}
, at: copy_net_ns+0x41e/0x780 net/core/net_namespace.c:577
 #1: 
ffffffff8aaf8e68
 (
rtnl_mutex
){+.+.}-{4:4}
, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
, at: register_netdevice_notifier_net+0x23/0xb0 net/core/dev.c:2102
2 locks held by syz-executor/6402:
 #0: 
ffffffff8aae0830
 (
pernet_ops_rwsem
){++++}-{4:4}
, at: copy_net_ns+0x41e/0x780 net/core/net_namespace.c:577
 #1: 
ffffffff8aaf8e68
 (
rtnl_mutex
){+.+.}-{4:4}
, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
, at: register_netdevice_notifier_net+0x23/0xb0 net/core/dev.c:2102
2 locks held by syz-executor/6404:
 #0: 
ffffffff8aae0830
 (
pernet_ops_rwsem
){++++}-{4:4}
, at: copy_net_ns+0x41e/0x780 net/core/net_namespace.c:577
 #1: 
ffffffff8aaf8e68
 (
rtnl_mutex
){+.+.}-{4:4}
, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
, at: register_netdevice_notifier_net+0x23/0xb0 net/core/dev.c:2102
2 locks held by syz-executor/6426:
 #0: 
ffffffff8aae0830
 (
pernet_ops_rwsem
){++++}-{4:4}
, at: copy_net_ns+0x41e/0x780 net/core/net_namespace.c:577
 #1: 
ffffffff8aaf8e68
 (
rtnl_mutex
){+.+.}-{4:4}
, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
, at: register_netdevice_notifier_net+0x23/0xb0 net/core/dev.c:2102
2 locks held by syz-executor/6428:
 #0: 
ffffffff8aae0830
 (pernet_ops_rwsem
){++++}-{4:4}
, at: copy_net_ns+0x41e/0x780 net/core/net_namespace.c:577
 #1: 
ffffffff8aaf8e68
 (
rtnl_mutex
){+.+.}-{4:4}
, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
, at: register_netdevice_notifier_net+0x23/0xb0 net/core/dev.c:2102
1 lock held by syz-executor/6445:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185
1 lock held by syz-executor/6446:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185
1 lock held by syz-executor/6447:
 #0: 
ffff888101298188
 (
&root->kernfs_rwsem
){++++}-{4:4}
, at: kernfs_dop_revalidate+0xa5/0x740 fs/kernfs/dir.c:1185

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xd25/0x1050 kernel/hung_task.c:515
 kthread+0x370/0x450 kernel/kthread.c:467
 ret_from_fork+0x6c3/0xcb0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
gspca_pac7302 1-1:1.0: URB error -71, resubmitting
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 28 Comm: kworker/1:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events free_obj_work
RIP: 0010:its_return_thunk+0x0/0x10 arch/x86/lib/retpoline.S:417
Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc <c3> cc 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 e9 2b e0 ed f9 cc
RSP: 0018:ffffc900001a8298 EFLAGS: 00000046
RAX: ffffc900001a8598 RBX: ffffffff878aa301 RCX: 000000000000005b
RDX: 0000000000000000 RSI: ffffffff878aa300 RDI: ffffc900001a8598
RBP: ffffc900001a8390 R08: 0000000000000001 R09: fffff520000350b3
R10: ffffc900001a8598 R11: 00000000001abce8 R12: 0000000000000000
R13: 0000000000000001 R14: ffffffff878aa300 R15: 000000007fffffff
FS:  0000000000000000(0000) GS:ffff8882687d3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000094ae000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 vsnprintf+0x7e2/0x1240 lib/vsprintf.c:2899
 sprintf+0xcc/0x100 lib/vsprintf.c:3111
 print_time kernel/printk/printk.c:1359 [inline]
 info_print_prefix+0x25a/0x350 kernel/printk/printk.c:1385
 record_print_text+0x143/0x3c0 kernel/printk/printk.c:1434
 printk_get_next_message+0x2d1/0x6c0 kernel/printk/printk.c:3072
 console_emit_next_record kernel/printk/printk.c:3137 [inline]
 console_flush_one_record+0x67c/0xe50 kernel/printk/printk.c:3269
 console_flush_all kernel/printk/printk.c:3343 [inline]
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0x103/0x260 kernel/printk/printk.c:3413
 vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
 _printk+0xcf/0x110 kernel/printk/printk.c:2504
 int_irq.cold+0x1a/0x7f drivers/media/usb/gspca/gspca.c:104
 __usb_hcd_giveback_urb+0x38d/0x610 drivers/usb/core/hcd.c:1657
 usb_hcd_giveback_urb+0x3ca/0x4a0 drivers/usb/core/hcd.c:1741
 dummy_timer+0xd85/0x3670 drivers/usb/gadget/udc/dummy_hcd.c:1995
 __run_hrtimer kernel/time/hrtimer.c:1785 [inline]
 __hrtimer_run_queues+0x50e/0xa70 kernel/time/hrtimer.c:1849
 hrtimer_run_softirq+0x17d/0x350 kernel/time/hrtimer.c:1866
 handle_softirqs+0x1de/0x9d0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xed/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+0x8f/0xb0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lockdep_enabled kernel/locking/lockdep.c:118 [inline]
RIP: 0010:lock_release+0x46/0x320 kernel/locking/lockdep.c:5881
Code: 89 6c 24 10 48 89 f5 0f 1f 44 00 00 65 8b 05 45 18 66 0b 83 f8 07 0f 87 1d 02 00 00 48 0f a3 05 d0 2a 61 09 0f 82 18 02 00 00 <44> 8b 05 77 3a 61 09 45 85 c0 0f 84 48 01 00 00 65 8b 05 0b 5c 66
RSP: 0018:ffffc900001e76c0 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffffff896e05a0 RCX: ffffffff8b536201
RDX: 0000000000000000 RSI: ffffffff87afa3a0 RDI: ffffffff891a2be8
RBP: ffffffff816f75ce R08: 0000000000000001 R09: 0000000000000007
R10: 0000000000000200 R11: 0000000000007d46 R12: ffffc900001e77c8
R13: ffffc900001e7778 R14: ffffc900001e7dc0 R15: ffffc900001e77ac
 rcu_lock_release include/linux/rcupdate.h:322 [inline]
 rcu_read_unlock include/linux/rcupdate.h:881 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1193 [inline]
 unwind_next_frame+0x3c3/0x1ea0 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x94/0xf0 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x43/0x70 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2687 [inline]
 slab_free mm/slub.c:6124 [inline]
 kmem_cache_free+0x105/0x640 mm/slub.c:6254
 free_object_list.isra.0+0xf8/0x2a0 lib/debugobjects.c:326
 free_obj_work+0x19d/0x3d0 lib/debugobjects.c:513
 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
 process_scheduled_works kernel/workqueue.c:3358 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
 kthread+0x370/0x450 kernel/kthread.c:467
 ret_from_fork+0x6c3/0xcb0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/01 21:28 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing bb375c251ab4 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb INFO: task hung in pick_next_task_fair
* Struck through repros no longer work on HEAD.