INFO: task kworker/u4:8:579 blocked for more than 143 seconds. Not tainted 5.5.0-rc6-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:8 D24432 579 2 0x80004000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:3385 [inline] __schedule+0x934/0x1f90 kernel/sched/core.c:4081 schedule+0xdc/0x2b0 kernel/sched/core.c:4155 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4214 __mutex_lock_common kernel/locking/mutex.c:1033 [inline] __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118 hashlimit_proc_net_exit net/netfilter/xt_hashlimit.c:1267 [inline] hashlimit_net_exit+0x16d/0x3d0 net/netfilter/xt_hashlimit.c:1290 ops_exit_list.isra.0+0xb1/0x160 net/core/net_namespace.c:172 cleanup_net+0x538/0xaf0 net/core/net_namespace.c:597 process_one_work+0x9af/0x1740 kernel/workqueue.c:2264 worker_thread+0x98/0xe40 kernel/workqueue.c:2410 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Showing all locks held in the system: 4 locks held by kworker/u4:8/579: #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: __write_once_size include/linux/compiler.h:226 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline] #0: ffff88821b78e528 ((wq_completion)netns){+.+.}, at: process_one_work+0x88b/0x1740 kernel/workqueue.c:2235 #1: ffffc90002ec7dc0 (net_cleanup_work){+.+.}, at: process_one_work+0x8c1/0x1740 kernel/workqueue.c:2239 #2: ffffffff8a4c6248 (pernet_ops_rwsem){++++}, at: cleanup_net+0xae/0xaf0 net/core/net_namespace.c:559 #3: ffffffff8a5500c0 (hashlimit_mutex){+.+.}, at: hashlimit_proc_net_exit net/netfilter/xt_hashlimit.c:1267 [inline] #3: ffffffff8a5500c0 (hashlimit_mutex){+.+.}, at: hashlimit_net_exit+0x16d/0x3d0 net/netfilter/xt_hashlimit.c:1290 1 lock held by khungtaskd/1126: #0: ffffffff899a3f00 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5334 1 lock held by rsyslogd/9609: #0: ffff8880a80d6da0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:801 2 locks held by getty/9699: #0: ffff88809f01e090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017532e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9700: #0: ffff8880a6b26090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017cb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9701: #0: ffff88809ff34090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000179b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9702: #0: ffff8880a8c8d090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017db2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9703: #0: ffff8880a9652090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017bb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9704: #0: ffff8880a9001090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017ab2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/9705: #0: ffff8880a24cd090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000172b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.0/4702: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1126 Comm: khungtaskd Not tainted 5.5.0-rc6-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+0x197/0x210 lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xb11/0x10c0 kernel/hung_task.c:289 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 4271 Comm: udevd Not tainted 5.5.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline] RIP: 0010:write_comp_data+0x0/0x70 kernel/kcov.c:207 Code: 83 fa 02 75 20 48 8b 88 88 13 00 00 8b 80 84 13 00 00 48 8b 11 48 83 c2 01 48 39 d0 76 07 48 89 34 d1 48 89 11 5d c3 0f 1f 00 <65> 4c 8b 04 25 c0 1e 02 00 65 8b 05 a8 28 8d 7e a9 00 01 1f 00 75 RSP: 0018:ffffc90001277cc8 EFLAGS: 00000282 RAX: 000000003ad09d16 RBX: ffff8880a953b000 RCX: ffffffff81d1684f RDX: 0000000000000854 RSI: 0000000225c17d03 RDI: 0000000000000007 RBP: ffffc90001277cd0 R08: ffff8880934e41c0 R09: 0000000000000000 R10: ffffed1012874108 R11: 0000000000000000 R12: 1ffff9200024efa6 R13: ffff8880a953b110 R14: 7fffffffffffffff R15: 0000000000000854 FS: 00007f09073b07a0(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000000 CR3: 0000000097119000 CR4: 00000000001426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ktime_set include/linux/ktime.h:39 [inline] timespec64_to_ktime include/linux/ktime.h:78 [inline] ep_poll+0x3df/0xe60 fs/eventpoll.c:1820 do_epoll_wait+0x210/0x260 fs/eventpoll.c:2273 __do_sys_epoll_wait fs/eventpoll.c:2283 [inline] __se_sys_epoll_wait fs/eventpoll.c:2280 [inline] __x64_sys_epoll_wait+0x97/0xf0 fs/eventpoll.c:2280 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f0906ac4943 Code: 00 31 d2 48 29 c2 64 89 11 48 83 c8 ff eb ea 90 90 90 90 90 90 90 90 83 3d b5 dc 2a 00 00 75 13 49 89 ca b8 e8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 3b c4 00 00 48 89 04 24 RSP: 002b:00007fff4ad5d2b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8 RAX: ffffffffffffffda RBX: 0000000000000bb8 RCX: 00007f0906ac4943 RDX: 0000000000000008 RSI: 00007fff4ad5d3b0 RDI: 000000000000000a RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000bb8 R11: 0000000000000246 R12: 0000000000000003 R13: 0000000000000000 R14: 00000000017c79c0 R15: 00000000017c2250