INFO: task kworker/u4:0:7 blocked for more than 143 seconds. Not tainted 5.6.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:0 D24848 7 2 0x80004000 Workqueue: events_unbound flush_to_ldisc Call Trace: context_switch kernel/sched/core.c:3386 [inline] __schedule+0x87f/0xcd0 kernel/sched/core.c:4082 schedule+0x188/0x210 kernel/sched/core.c:4156 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4215 __mutex_lock_common+0x11f1/0x2f30 kernel/locking/mutex.c:1033 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118 flush_to_ldisc+0x39/0x550 drivers/tty/tty_buffer.c:505 process_one_work+0x7f5/0x10f0 kernel/workqueue.c:2264 worker_thread+0xbbc/0x1630 kernel/workqueue.c:2410 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 INFO: task login:8900 blocked for more than 143 seconds. Not tainted 5.6.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. login D24280 8900 1 0x00004004 Call Trace: context_switch kernel/sched/core.c:3386 [inline] __schedule+0x87f/0xcd0 kernel/sched/core.c:4082 schedule+0x188/0x210 kernel/sched/core.c:4156 schedule_timeout+0x46/0x240 kernel/time/timer.c:1871 do_wait_for_common+0x2e7/0x4d0 kernel/sched/completion.c:83 __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x47/0x60 kernel/sched/completion.c:136 __flush_work+0xcf/0x130 kernel/workqueue.c:3041 flush_work+0x17/0x20 kernel/workqueue.c:3062 tty_buffer_flush_work+0x19/0x20 drivers/tty/tty_buffer.c:618 n_tty_read+0x6ce/0x1bc0 drivers/tty/n_tty.c:2199 tty_read+0x15f/0x310 drivers/tty/tty_io.c:869 __vfs_read+0xb8/0x730 fs/read_write.c:425 vfs_read+0x1d8/0x420 fs/read_write.c:461 ksys_read+0x117/0x220 fs/read_write.c:587 __do_sys_read fs/read_write.c:597 [inline] __se_sys_read fs/read_write.c:595 [inline] __x64_sys_read+0x7b/0x90 fs/read_write.c:595 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f0117220310 Code: Bad RIP value. RSP: 002b:00007fffff7540e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0117220310 RDX: 00000000000001ff RSI: 00007fffff754350 RDI: 0000000000000000 RBP: 0000000000000000 R08: 00007f0117b03700 R09: 0000000000000000 R10: 00007fffff7540a0 R11: 0000000000000246 R12: 00007fffff754350 R13: 0000000000000000 R14: 0000000000000001 R15: 000000000060b798 Showing all locks held in the system: 3 locks held by kworker/u4:0/7: #0: ffff8880aa433928 ((wq_completion)events_unbound){+.+.}, at: spin_unlock_irq include/linux/spinlock.h:388 [inline] #0: ffff8880aa433928 ((wq_completion)events_unbound){+.+.}, at: process_one_work+0x763/0x10f0 kernel/workqueue.c:2237 #1: ffffc90000cdfd78 ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0x7a5/0x10f0 kernel/workqueue.c:2239 #2: ffff8880aa5be0a8 (&buf->lock){+.+.}, at: flush_to_ldisc+0x39/0x550 drivers/tty/tty_buffer.c:505 1 lock held by khungtaskd/1112: #0: ffffffff892d98c8 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 include/linux/rcupdate.h:207 2 locks held by rs:main Q:Reg/8808: #0: ffff888099a91860 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x279/0x310 fs/file.c:821 #1: ffff8882145ac428 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2903 [inline] #1: ffff8882145ac428 (sb_writers#3){.+.+}, at: vfs_write+0x24e/0x580 fs/read_write.c:557 1 lock held by rsyslogd/8810: #0: ffff88809f7c4360 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x279/0x310 fs/file.c:821 2 locks held by login/8900: #0: ffff88809f946090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017ab2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8901: #0: ffff8880995a0090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000182b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8902: #0: ffff888096f33090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000180b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8903: #0: ffff8880a1ce1090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017eb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8904: #0: ffff8880a6310090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017bb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8905: #0: ffff88808cd9b090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017cb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8906: #0: ffff88808ebc3090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017732e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 4 locks held by syz-executor.5/27196: 1 lock held by syz-executor.2/27237: #0: ffff88809f946090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1112 Comm: khungtaskd Not tainted 5.6.0-rc1-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+0x1fb/0x318 lib/dump_stack.c:118 nmi_cpu_backtrace+0xaa/0x190 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x16f/0x290 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace+0x17/0x20 include/linux/nmi.h:146 check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xd40/0xd60 kernel/hung_task.c:289 kthread+0x332/0x350 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: 27196 Comm: syz-executor.5 Not tainted 5.6.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:match_held_lock+0x8/0x270 kernel/locking/lockdep.c:4012 Code: 89 e8 4c 9a 57 00 83 3d b9 5a 0d 08 00 0f 85 47 ff ff ff eb 86 0f 0b 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 <41> 55 41 54 53 50 49 89 f5 49 89 fc 48 ba 00 00 00 00 00 fc ff df RSP: 0018:ffffc900029d7810 EFLAGS: 00000046 RAX: 1ffffffff1255a00 RBX: ffff888099e08cb8 RCX: ffff888099e08a20 RDX: dffffc0000000000 RSI: ffff8880aeb37198 RDI: ffff888099e08c98 RBP: ffffc900029d7820 R08: dffffc0000000000 R09: ffffed10133c1081 R10: ffffed10133c1081 R11: 0000000000000000 R12: ffff888099e08c90 R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff110133c1192 FS: 00007f4854c88700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffff600400 CR3: 000000009144d000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: __lock_is_held kernel/locking/lockdep.c:4305 [inline] lock_is_held_type+0x11d/0x2b0 kernel/locking/lockdep.c:4521 lock_is_held include/linux/lockdep.h:361 [inline] rq_clock_task kernel/sched/sched.h:1104 [inline] update_curr+0x9a/0xd00 kernel/sched/fair.c:835 pick_next_task_fair+0x107/0x10c0 kernel/sched/fair.c:6704 pick_next_task kernel/sched/core.c:3922 [inline] __schedule+0x3e8/0xcd0 kernel/sched/core.c:4052 schedule+0x188/0x210 kernel/sched/core.c:4156 paste_selection+0x269/0x400 drivers/tty/vt/selection.c:367 tioclinux+0x121/0x530 drivers/tty/vt/vt.c:3044 vt_ioctl+0x3f1/0x3a70 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0xee6/0x15c0 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl fs/ioctl.c:763 [inline] __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl+0x113/0x190 fs/ioctl.c:770 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:770 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45b3b9 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:00007f4854c87c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f4854c886d4 RCX: 000000000045b3b9 RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000056c R14: 00000000004c6b63 R15: 000000000075bf2c