INFO: task kworker/u4:6:263 blocked for more than 143 seconds. Not tainted 5.9.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u4:6 state:D stack:24128 pid: 263 ppid: 2 flags:0x00004000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:3778 [inline] __schedule+0xea9/0x2230 kernel/sched/core.c:4527 schedule+0xd0/0x2a0 kernel/sched/core.c:4602 schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1855 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+0x163/0x260 kernel/sched/completion.c:138 __flush_work+0x51f/0xab0 kernel/workqueue.c:3046 flush_all_backlogs net/core/dev.c:5635 [inline] rollback_registered_many+0x552/0x1210 net/core/dev.c:9269 unregister_netdevice_many.part.0+0x1a/0x2f0 net/core/dev.c:10429 unregister_netdevice_many+0x36/0x50 net/core/dev.c:10428 ip6gre_exit_batch_net+0x4cf/0x6c0 net/ipv6/ip6_gre.c:1609 ops_exit_list+0x10d/0x160 net/core/net_namespace.c:189 cleanup_net+0x4ea/0xa00 net/core/net_namespace.c:603 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 Showing all locks held in the system: 5 locks held by kworker/u4:6/263: #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8880a9797138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240 #1: ffffc90001627da8 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244 #2: ffffffff8a7dd2f0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xa00 net/core/net_namespace.c:565 #3: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: ip6gre_exit_batch_net+0x82/0x6c0 net/ipv6/ip6_gre.c:1606 #4: ffffffff89b91650 (cpu_hotplug_lock){++++}-{0:0}, at: get_online_cpus include/linux/cpu.h:144 [inline] #4: ffffffff89b91650 (cpu_hotplug_lock){++++}-{0:0}, at: flush_all_backlogs net/core/dev.c:5628 [inline] #4: ffffffff89b91650 (cpu_hotplug_lock){++++}-{0:0}, at: rollback_registered_many+0x45b/0x1210 net/core/dev.c:9269 1 lock held by khungtaskd/1173: #0: ffffffff89bd6a40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5829 6 locks held by kworker/0:1H/2457: 1 lock held by in:imklog/6527: #0: ffff8880a69090f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930 3 locks held by kworker/1:11/17433: #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff888214c99938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240 #1: ffffc90005417da8 ((addr_chk_work).work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244 #2: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4568 1 lock held by syz-executor.5/24535: #0: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:705 [inline] #0: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3a/0x180 drivers/net/tun.c:3408 1 lock held by syz-executor.0/24730: #0: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:705 [inline] #0: ffffffff8a7ea348 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3a/0x180 drivers/net/tun.c:3408 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1173 Comm: khungtaskd Not tainted 5.9.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline] watchdog+0xd7d/0x1000 kernel/hung_task.c:295 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 2457 Comm: kworker/0:1H Not tainted 5.9.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_highpri snd_vmidi_output_work RIP: 0010:__snd_rawmidi_transmit_ack+0x9f/0x300 sound/core/rawmidi.c:1252 Code: 48 89 c2 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 fb 01 00 00 4c 8b 7b 38 48 8d 7b 18 4c 63 f5 <48> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 4d 01 f7 80 3c RSP: 0018:ffffc9000768fbd0 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: ffff88805fab6400 RCX: ffffffff861403f9 RDX: 1ffff1100bf56c87 RSI: ffffffff8613f791 RDI: ffff88805fab6418 RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000003 R10: 0000000000000000 R11: 0000000000000001 R12: ffff88809a4bce00 R13: ffff88805fab6450 R14: 0000000000000001 R15: 0000000000000260 FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000744138 CR3: 0000000095401000 CR4: 00000000001526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: snd_rawmidi_transmit+0xae/0xf0 sound/core/rawmidi.c:1314 snd_vmidi_output_work+0x108/0x380 sound/core/seq/seq_virmidi.c:144 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294