INFO: task kworker/u4:4:247 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/u4:4 D24128 247 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 getty:8774 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. getty D24280 8774 1 0x80004002 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 down_write_failed+0x2f5/0x7d0 drivers/tty/tty_ldsem.c:262 __ldsem_down_write_nested drivers/tty/tty_ldsem.c:324 [inline] ldsem_down_write+0xac/0xf0 drivers/tty/tty_ldsem.c:366 __tty_ldisc_lock drivers/tty/tty_ldisc.c:315 [inline] tty_ldisc_lock+0x6e/0xb0 drivers/tty/tty_ldisc.c:339 tty_ldisc_hangup+0x24a/0x6b0 drivers/tty/tty_ldisc.c:745 __tty_hangup+0x4d4/0x770 drivers/tty/tty_io.c:625 tty_vhangup_session+0x1a/0x20 drivers/tty/tty_io.c:735 disassociate_ctty+0x25f/0x6d0 drivers/tty/tty_jobctrl.c:267 do_exit+0x5b2/0x2000 kernel/exit.c:799 do_group_exit+0x15c/0x2b0 kernel/exit.c:899 __do_sys_exit_group+0x17/0x20 kernel/exit.c:910 __se_sys_exit_group+0x14/0x20 kernel/exit.c:908 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:908 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fe61203d1e8 Code: Bad RIP value. RSP: 002b:00007fffc24a1f28 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fe61203d1e8 RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 RBP: 00007fe612312840 R08: 00000000000000e7 R09: ffffffffffffffa8 R10: 00007fe612318740 R11: 0000000000000246 R12: 00007fe612312840 R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 3 locks held by kworker/u4:4/247: #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: ffffc90001b57d78 ((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/1138: #0: ffffffff892d98c8 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 include/linux/rcupdate.h:207 1 lock held by rsyslogd/8684: #0: ffff88809d5270e0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x279/0x310 fs/file.c:821 2 locks held by getty/8774: #0: ffff88809e36b198 (&tty->legacy_mutex){+.+.}, at: tty_lock+0xa6/0x110 drivers/tty/tty_mutex.c:19 #1: ffff88809e36b090 (&tty->ldisc_sem){++++}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:315 [inline] #1: ffff88809e36b090 (&tty->ldisc_sem){++++}, at: tty_ldisc_lock+0x6e/0xb0 drivers/tty/tty_ldisc.c:339 2 locks held by getty/8775: #0: ffff8880a772a090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000185b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8776: #0: ffff8880934f9090 (&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/8777: #0: ffff88809d1c9090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000183b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8778: #0: ffff88808f8dd090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000184b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8779: #0: ffff88808d047090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc900017fb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 2 locks held by getty/8780: #0: ffff88809ea7f090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffffc9000179b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156 3 locks held by syz-executor.0/15815: ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1138 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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 15815 Comm: syz-executor.0 Not tainted 5.6.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:check_memory_region+0x6/0x2f0 mm/kasan/generic.c:191 Code: 0c 31 db 48 c7 c7 bb fe e6 88 4c 89 fe 31 c0 e8 b3 ad ab ff eb cf cc cc cc cc cc cc cc cc cc cc cc cc cc cc 55 48 89 e5 41 57 <41> 56 41 55 41 54 53 b0 01 48 85 f6 0f 84 09 02 00 00 48 89 fb 48 RSP: 0018:ffffc90014697840 EFLAGS: 00000046 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81640736 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8969b460 RBP: ffffc90014697848 R08: ffffffff83a4d187 R09: ffffed1015d47004 R10: ffffed1015d47004 R11: 0000000000000000 R12: dffffc0000000000 R13: ffff8880a9158200 R14: ffff8880aea37f55 R15: ffff8880aea37f40 FS: 00007fc4c4317700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c00c8a3810 CR3: 0000000092ad0000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __kasan_check_read+0x11/0x20 mm/kasan/common.c:95 test_bit include/asm-generic/bitops/instrumented-non-atomic.h:110 [inline] cpumask_test_cpu include/linux/cpumask.h:360 [inline] trace_rcu_utilization+0x126/0x1e0 include/trace/events/rcu.h:27 rcu_note_context_switch+0x1c7/0xdf0 kernel/rcu/tree_plugin.h:332 __schedule+0xd3/0xcd0 kernel/sched/core.c:4020 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:00007fc4c4316c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fc4c43176d4 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