syzbot

INFO: task kworker/u8:3:50 blocked for more than 143 seconds.
      Tainted: G     U  W    L XTNJ syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:3    state:D stack:23544 pid:50    tgid:50    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common+0x2fc/0x4e0 kernel/sched/completion.c:121
 __flush_workqueue+0x3e2/0x1230 kernel/workqueue.c:4029
 rds_tcp_listen_stop+0x104/0x150 net/rds/tcp_listen.c:331
 rds_tcp_kill_sock net/rds/tcp.c:611 [inline]
 rds_tcp_exit_net+0xcb/0x810 net/rds/tcp.c:634
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
 cleanup_net+0x41b/0x8b0 net/core/net_namespace.c:695
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
1 lock held by ksoftirqd/1/23:
1 lock held by khungtaskd/31:
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8e3c45e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:3/50:
 #0: ffff88801ba9f148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90000bb7d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff900d48d0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xad/0x8b0 net/core/net_namespace.c:669
4 locks held by kworker/1:4/5918:
1 lock held by syz.2.1517/9638:
 #0: ffffffff900ead08 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff900ead08 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x38/0x230 drivers/net/tun.c:3436
3 locks held by kworker/u10:5/31381:
 #0: ffff88813ff29948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90004697d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff900ead08 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0x51/0xc0 net/core/link_watch.c:303
1 lock held by syz.0.9098/31911:
 #0: ffffffff900d48d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576
3 locks held by kworker/1:5/31927:
 #0: ffff88813ff15948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc9000f0c7d00 (free_ipc_work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff8e3cfb78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343
2 locks held by getty/31973:
 #0: ffff88814dc9d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000c06b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
1 lock held by syz.6.9284/32703:
 #0: ffffffff900d48d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576
1 lock held by syz.1.9300/306:
 #0: ffffffff900d48d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576
1 lock held by syz-executor/452:
5 locks held by udevd/733:
 #0: ffff8880b843a4d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:646 [inline]
 #0: ffff8880b843a4d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x7e/0x130 kernel/sched/core.c:631
 #1: ffff88808ef56018 (&pid_list->lock){-.-.}-{2:2}, at: trace_pid_list_is_set+0x4c/0x150 kernel/trace/pid_list.c:141
 #2: ffff88807dd05958 (&ep->lock){....}-{3:3}, at: ep_poll_callback+0x80/0xbc0 fs/eventpoll.c:1256
 #3: ffff88807dd058a8 (&ep->wq){....}-{3:3}, at: __wake_up_common_lock kernel/sched/wait.c:124 [inline]
 #3: ffff88807dd058a8 (&ep->wq){....}-{3:3}, at: __wake_up_sync_key kernel/sched/wait.c:192 [inline]
 #3: ffff88807dd058a8 (&ep->wq){....}-{3:3}, at: __wake_up_sync+0x17/0x50 kernel/sched/wait.c:224
 #4: ffff88807e68e528 (&p->pi_lock){-.-.}-{2:2}, at: class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:557 [inline]
 #4: ffff88807e68e528 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0xb7/0x1870 kernel/sched/core.c:4181
1 lock held by syz.5.9414/867:
 #0: ffffffff900d48d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Tainted: G     U  W    L XTNJ syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER, [W]=WARN, [L]=SOFTLOCKUP, [X]=AUX, [T]=RANDSTRUCT, [N]=TEST, [J]=FWCTL
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
 watchdog+0xf3f/0x1170 kernel/hung_task.c:495
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 32661 Comm: kworker/u10:9 Tainted: G     U  W    L XTNJ syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER, [W]=WARN, [L]=SOFTLOCKUP, [X]=AUX, [T]=RANDSTRUCT, [N]=TEST, [J]=FWCTL
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4879 [inline]
RIP: 0010:__lock_acquire+0x336/0x1c90 kernel/locking/lockdep.c:5187
Code: d0 41 83 c6 01 44 3b b5 28 0b 00 00 7d 30 49 63 c6 48 8d 04 80 41 0f b7 44 c4 20 66 25 ff 1f 0f b7 c0 48 0f a3 05 da c4 0f 14 <72> ab 8b 05 32 70 18 19 85 c0 0f 84 f8 00 00 00 31 c9 eb a9 44 38
RSP: 0018:ffffc90003087848 EFLAGS: 00000003
RAX: 0000000000000f52 RBX: 0000000000000004 RCX: ffffffff95ae39a0
RDX: 0000000000000005 RSI: 0000000000000004 RDI: ffff88802f60aa10
RBP: ffff88802f609e40 R08: 0000000000080000 R09: 0000000000000001
R10: 00000000000000a0 R11: 0000000000000001 R12: ffff88802f60a970
R13: ffff88802f60aa10 R14: 0000000000000002 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff888124a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555da41f6860 CR3: 000000000e182000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
 __debug_check_no_obj_freed lib/debugobjects.c:1088 [inline]
 debug_check_no_obj_freed+0x1c9/0x600 lib/debugobjects.c:1129
 slab_free_hook mm/slub.c:2474 [inline]
 slab_free mm/slub.c:6642 [inline]
 kmem_cache_free+0x2ad/0x6c0 mm/slub.c:6752
 kfree_skbmem+0x1a4/0x1f0 net/core/skbuff.c:1110
 __kfree_skb net/core/skbuff.c:1167 [inline]
 consume_skb net/core/skbuff.c:1398 [inline]
 consume_skb+0xcc/0x100 net/core/skbuff.c:1392
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:836 [inline]
 nsim_dev_trap_report_work+0x8bd/0xcf0 drivers/net/netdevsim/dev.c:866
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>