syzbot


INFO: task hung in flush_to_ldisc (3)

Status: auto-closed as invalid on 2021/07/07 16:40
Reported-by: syzbot+9fd69af2d10798b20f19@syzkaller.appspotmail.com
First crash: 476d, last: 476d
similar bugs (8):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 INFO: task hung in flush_to_ldisc (2) 1 714d 714d 0/1 auto-closed as invalid on 2020/11/11 17:44
upstream INFO: task hung in flush_to_ldisc (2) 1 445d 445d 0/22 auto-closed as invalid on 2021/06/09 11:04
linux-4.19 INFO: task hung in flush_to_ldisc 10 864d 926d 0/1 auto-closed as invalid on 2020/06/15 14:09
upstream INFO: task hung in flush_to_ldisc C inconclusive done 15 866d 936d 17/22 fixed on 2020/11/16 12:12
upstream INFO: task hung in flush_to_ldisc (3) C inconclusive 3 145d 334d 0/22 closed as invalid on 2022/02/08 10:26
linux-4.14 INFO: task hung in flush_to_ldisc (2) 1 668d 668d 0/1 auto-closed as invalid on 2020/12/28 13:53
linux-4.19 INFO: task hung in flush_to_ldisc (3) 1 428d 428d 0/1 auto-closed as invalid on 2021/08/25 00:39
linux-4.14 INFO: task hung in flush_to_ldisc 8 856d 926d 0/1 auto-closed as invalid on 2020/06/23 11:01

Sample crash report:
bond0 (unregistering): Releasing backup interface bond_slave_0
bond0 (unregistering): Released all slaves
device hsr_slave_1 left promiscuous mode
device hsr_slave_0 left promiscuous mode
bond0 (unregistering): Released all slaves
INFO: task kworker/u4:4:2873 blocked for more than 140 seconds.
      Not tainted 4.14.224-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:4    D25784  2873      2 0x80000000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3486
 __mutex_lock_common kernel/locking/mutex.c:833 [inline]
 __mutex_lock+0x669/0x1310 kernel/locking/mutex.c:893
 flush_to_ldisc+0x35/0x3f0 drivers/tty/tty_buffer.c:499
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
INFO: task agetty:4232 blocked for more than 140 seconds.
      Not tainted 4.14.224-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
agetty          D27864  4232      1 0x80000002
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x80a/0xe90 kernel/time/timer.c:1724
 down_write_failed drivers/tty/tty_ldsem.c:298 [inline]
 __ldsem_down_write_nested+0x2b9/0x700 drivers/tty/tty_ldsem.c:360
 __tty_ldisc_lock drivers/tty/tty_ldisc.c:332 [inline]
 tty_ldisc_lock+0x4d/0x80 drivers/tty/tty_ldisc.c:356
 tty_ldisc_hangup+0x1d3/0x6c0 drivers/tty/tty_ldisc.c:758
 __tty_hangup.part.0+0x31a/0x730 drivers/tty/tty_io.c:622
 __tty_hangup drivers/tty/tty_io.c:572 [inline]
 tty_vhangup_session+0x20/0x30 drivers/tty/tty_io.c:732
 disassociate_ctty.part.0+0x98/0x750 drivers/tty/tty_jobctrl.c:266
 disassociate_ctty+0x71/0x90 drivers/tty/tty_jobctrl.c:260
 do_exit+0x162a/0x2850 kernel/exit.c:866
 do_group_exit+0x100/0x2e0 kernel/exit.c:965
 SYSC_exit_group kernel/exit.c:976 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:974
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f024fd16618
RSP: 002b:00007ffc831ff8d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f024fd16618
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 00007f024fff38e0 R08: 00000000000000e7 R09: ffffffffffffff98
R10: 00007ffc831ff858 R11: 0000000000000246 R12: 00007f024fff38e0
R13: 00007f024fff8c20 R14: 0000000000000001 R15: 000000000000000a
INFO: task syz-executor.0:6100 blocked for more than 140 seconds.
      Not tainted 4.14.224-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D28880  6100  31887 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3486
 __mutex_lock_common kernel/locking/mutex.c:833 [inline]
 __mutex_lock+0x669/0x1310 kernel/locking/mutex.c:893
 paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373
 tioclinux+0xfd/0x490 drivers/tty/vt/vt.c:2714
 vt_ioctl+0x11bd/0x1d50 drivers/tty/vt/vt_ioctl.c:372
 tty_ioctl+0x50f/0x13c0 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x465f69
RSP: 002b:00007f4d0e77d188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465f69
RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000004
RBP: 00000000004bfa3f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffe3b348a7f R14: 00007f4d0e77d300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1531:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff86ff2967>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
3 locks held by kworker/u4:4/2873:
 #0:  ("events_unbound"){+.+.}, at: [<ffffffff81363810>] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087
 #1:  ((&buf->work)){+.+.}, at: [<ffffffff81363846>] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091
 #2:  (&buf->lock){+.+.}, at: [<ffffffff83539815>] flush_to_ldisc+0x35/0x3f0 drivers/tty/tty_buffer.c:499
2 locks held by agetty/7698:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff83536f82>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8352c303>] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156
2 locks held by agetty/4232:
 #0:  (&tty->legacy_mutex){+.+.}, at: [<ffffffff8353d3ff>] tty_lock+0x5f/0x70 drivers/tty/tty_mutex.c:19
 #1:  (&tty->ldisc_sem){++++}, at: [<ffffffff83537aad>] __tty_ldisc_lock drivers/tty/tty_ldisc.c:332 [inline]
 #1:  (&tty->ldisc_sem){++++}, at: [<ffffffff83537aad>] tty_ldisc_lock+0x4d/0x80 drivers/tty/tty_ldisc.c:356
2 locks held by syz-executor.1/6001:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff83536f82>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&buf->lock){+.+.}, at: [<ffffffff8355c2ae>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373
2 locks held by syz-executor.0/6100:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff83536f82>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&buf->lock){+.+.}, at: [<ffffffff8355c2ae>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1531 Comm: khungtaskd Not tainted 4.14.224-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x13a/0x180 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
 watchdog+0x5b9/0xb40 kernel/hung_task.c:274
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 8 Comm: rcu_preempt Not tainted 4.14.224-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880b5414200 task.stack: ffff8880b5418000
RIP: 0010:debug_object_free lib/debugobjects.c:604 [inline]
RIP: 0010:debug_object_free+0x112/0x320 lib/debugobjects.c:586
RSP: 0018:ffff8880b541fc60 EFLAGS: 00000097
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 000000000000141d
RDX: 1ffff1101442e144 RSI: 0000000000000001 RDI: ffff8880a2170a28
RBP: ffff8880a2170a10 R08: 0000000000000286 R09: 00000000000c0001
R10: ffff8880b5414a88 R11: ffff8880b5414200 R12: ffff8880a2170a20
R13: ffffffff88f7fec0 R14: ffff8880b541fd18 R15: ffffffff8bfb1a08
FS:  0000000000000000(0000) GS:ffff8880ba500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7b04a45000 CR3: 00000000a3647000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 destroy_timer_on_stack kernel/time/timer.c:724 [inline]
 schedule_timeout+0x4c6/0xe90 kernel/time/timer.c:1751
 rcu_gp_kthread+0xc0a/0x1e60 kernel/rcu/tree.c:2255
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: 08 04 4c 8d 65 10 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e f9 01 00 00 83 7d 10 03 <0f> 84 c2 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 ea 48 c1 

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2021/03/09 16:40 linux-4.14.y 1d177c0872ab 26967e35 .config log report info INFO: task hung in flush_to_ldisc