INFO: task kworker/u4:0:13246 blocked for more than 140 seconds. Not tainted 4.19.104-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:0 D25568 13246 2 0x80000000 Workqueue: events_unbound flush_to_ldisc Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x866/0x1dc0 kernel/sched/core.c:3515 schedule+0x92/0x1c0 kernel/sched/core.c:3559 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3617 __mutex_lock_common kernel/locking/mutex.c:1002 [inline] __mutex_lock+0x726/0x1300 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 flush_to_ldisc+0x3d/0x390 drivers/tty/tty_buffer.c:500 process_one_work+0x989/0x1750 kernel/workqueue.c:2153 worker_thread+0x98/0xe40 kernel/workqueue.c:2296 kthread+0x354/0x420 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 INFO: task getty:20061 blocked for more than 140 seconds. Not tainted 4.19.104-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. getty D27720 20061 1 0x00000000 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x866/0x1dc0 kernel/sched/core.c:3515 schedule+0x92/0x1c0 kernel/sched/core.c:3559 schedule_timeout+0x8c8/0xfc0 kernel/time/timer.c:1782 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136 __flush_work+0x49f/0x870 kernel/workqueue.c:2926 flush_work+0x18/0x20 kernel/workqueue.c:2947 tty_buffer_flush_work+0x16/0x19 drivers/tty/tty_buffer.c:613 n_tty_read+0xb1a/0x1b70 drivers/tty/n_tty.c:2197 tty_read+0x193/0x2a0 drivers/tty/tty_io.c:867 __vfs_read+0x114/0x800 fs/read_write.c:416 vfs_read+0x194/0x3d0 fs/read_write.c:452 ksys_read+0x14f/0x2d0 fs/read_write.c:579 __do_sys_read fs/read_write.c:589 [inline] __se_sys_read fs/read_write.c:587 [inline] __x64_sys_read+0x73/0xb0 fs/read_write.c:587 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f4815daa310 Code: Bad RIP value. RSP: 002b:00007ffddc614cd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f481647f6a8 RCX: 00007f4815daa310 RDX: 0000000000000001 RSI: 00007ffddc614d28 RDI: 0000000000000000 RBP: 00007ffddc615510 R08: 0000000000000000 R09: 00007f481647f700 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006075a0 R13: 00007ffddc617eda R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 1 lock held by khungtaskd/1080: #0: 000000005aa21001 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4438 1 lock held by rsyslogd/7790: #0: 0000000067fda98a (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:767 2 locks held by getty/7913: #0: 000000003c1aeae9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000002f1c1b2c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by getty/7914: #0: 000000000b24d01c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000019c1e0d2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by getty/7915: #0: 00000000625ceac9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000002dad0646 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by getty/7916: #0: 00000000b07210e3 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000003ac313ca (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by getty/7917: #0: 0000000024eff389 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000b4fc8cbe (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by getty/7918: #0: 000000003adf4022 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000006a006c79 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 3 locks held by kworker/u4:0/13246: #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000997e0484 ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0x87e/0x1750 kernel/workqueue.c:2124 #1: 0000000011939d2d ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128 #2: 00000000a1a408a8 (&buf->lock){+.+.}, at: flush_to_ldisc+0x3d/0x390 drivers/tty/tty_buffer.c:500 2 locks held by kworker/u4:2/28730: #0: 000000005a8d2e8b (&rq->lock){-.-.}, at: rq_lock kernel/sched/sched.h:1817 [inline] #0: 000000005a8d2e8b (&rq->lock){-.-.}, at: __schedule+0x1f8/0x1dc0 kernel/sched/core.c:3453 #1: 000000005aa21001 (rcu_read_lock){....}, at: trace_sched_stat_runtime include/trace/events/sched.h:428 [inline] #1: 000000005aa21001 (rcu_read_lock){....}, at: update_curr+0x2cc/0x8a0 kernel/sched/fair.c:844 2 locks held by getty/20061: #0: 00000000e200e7f0 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000006a3dbecc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154 2 locks held by syz-executor.4/1730: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1080 Comm: khungtaskd Not tainted 4.19.104-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+0x63/0xa4 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 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:203 [inline] watchdog+0x9df/0xee0 kernel/hung_task.c:287 kthread+0x354/0x420 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 1730 Comm: syz-executor.4 Not tainted 4.19.104-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:lock_is_held_type+0x17e/0x210 kernel/locking/lockdep.c:3943 Code: 00 00 00 fc ff df 41 c7 85 7c 08 00 00 00 00 00 00 48 c1 e8 03 80 3c 10 00 75 63 48 83 3d e1 c2 a0 07 00 74 30 48 89 df 57 9d <0f> 1f 44 00 00 48 83 c4 08 44 89 e0 5b 41 5c 41 5d 5d c3 48 83 c4 RSP: 0018:ffff88809750f640 EFLAGS: 00000082 RAX: 1ffffffff11e4ae9 RBX: 0000000000000082 RCX: ffff888046858d00 RDX: dffffc0000000000 RSI: ffffffff88fb7f40 RDI: 0000000000000082 RBP: ffff88809750f660 R08: 1ffff11015d24732 R09: ffffed1015d24733 R10: ffffed1015d24732 R11: ffff8880ae923993 R12: 0000000000000000 R13: ffff888046858480 R14: ffff888046858480 R15: 0000000000000000 FS: 00007fe0e3a9e700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffff600400 CR3: 0000000094d03000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: lock_is_held include/linux/lockdep.h:344 [inline] task_css include/linux/cgroup.h:482 [inline] task_ca kernel/sched/cpuacct.c:43 [inline] cpuacct_charge+0x273/0x360 kernel/sched/cpuacct.c:349 cgroup_account_cputime include/linux/cgroup.h:766 [inline] update_curr+0x2d7/0x8a0 kernel/sched/fair.c:845 pick_next_task_fair+0x6bf/0x1580 kernel/sched/fair.c:6737 pick_next_task kernel/sched/core.c:3361 [inline] __schedule+0x456/0x1dc0 kernel/sched/core.c:3489 schedule+0x92/0x1c0 kernel/sched/core.c:3559 paste_selection+0x2e8/0x443 drivers/tty/vt/selection.c:354 tioclinux+0x133/0x470 drivers/tty/vt/vt.c:3019 vt_ioctl+0x19ab/0x2530 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0x7f3/0x1510 drivers/tty/tty_io.c:2669 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688 ksys_ioctl+0xab/0xd0 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c6c9 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fe0e3a9dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fe0e3a9e6d4 RCX: 000000000045c6c9 RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000004 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000570 R14: 00000000004c7ec2 R15: 000000000076bf2c