syzbot


INFO: task hung in n_tty_read

Status: auto-closed as invalid on 2020/04/29 17:03
Reported-by: syzbot+916bff519eec470a8375@syzkaller.appspotmail.com
First crash: 972d, last: 961d
similar bugs (5):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 INFO: task hung in n_tty_read 6 904d 944d 0/1 auto-closed as invalid on 2020/06/25 03:18
android-44 INFO: task hung in n_tty_read 1 1055d 1055d 0/2 auto-closed as invalid on 2020/01/25 18:14
upstream INFO: task hung in n_tty_read (2) C error 1 499d 495d 0/23 upstream: reported C repro on 2021/04/09 23:49
upstream INFO: task hung in n_tty_read 3 921d 975d 0/23 auto-closed as invalid on 2020/05/09 10:39
linux-4.14 INFO: task hung in n_tty_read (2) 1 479d 479d 0/1 auto-closed as invalid on 2021/08/24 04:16

Sample crash report:
INFO: task login:7636 blocked for more than 140 seconds.
      Not tainted 4.19.92-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
login           D24416  7636      1 0x00000004
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: 0033:0x7fa13cc64310
Code: Bad RIP value.
RSP: 002b:00007fffdfcbaf88 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa13cc64310
RDX: 00000000000001ff RSI: 00007fffdfcbb1f0 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007fa13d547700 R09: 0000000000000000
R10: 00007fffdfcbaf40 R11: 0000000000000246 R12: 00007fffdfcbb1f0
R13: 0000000000000000 R14: 0000000000000001 R15: 000000000060b798
INFO: task kworker/u4:15:27613 blocked for more than 140 seconds.
      Not tainted 4.19.92-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:15   D25432 27613      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
 process_scheduled_works kernel/workqueue.c:2212 [inline]
 worker_thread+0x750/0xe40 kernel/workqueue.c:2301
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
INFO: task syz-executor.5:31892 blocked for more than 140 seconds.
      Not tainted 4.19.92-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D28480 31892  19642 0x00000004
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
 tty_buffer_lock_exclusive+0x30/0x40 drivers/tty/tty_buffer.c:61
 paste_selection+0x11d/0x443 drivers/tty/vt/selection.c:348
 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: 0033:0x45a9e9
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:00007f47e832ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a9e9
RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f47e832b6d4
R13: 00000000004c5db9 R14: 00000000004dc4d8 R15: 00000000ffffffff
INFO: task syz-executor.3:31896 blocked for more than 140 seconds.
      Not tainted 4.19.92-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D27536 31896  19645 0x00000004
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
 tty_buffer_lock_exclusive+0x30/0x40 drivers/tty/tty_buffer.c:61
 paste_selection+0x11d/0x443 drivers/tty/vt/selection.c:348
 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: 0033:0x45a9e9
Code: Bad RIP value.
RSP: 002b:00007fbbd42c8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a9e9
RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbbd42c96d4
R13: 00000000004c5db9 R14: 00000000004dc4d8 R15: 00000000ffffffff

Showing all locks held in the system:
1 lock held by khungtaskd/1068:
 #0: 00000000cc049aa7 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4438
1 lock held by rsyslogd/7511:
 #0: 0000000013591e1b (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:767
2 locks held by getty/7635:
 #0: 000000008f97365d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000debcf6a1 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by login/7636:
 #0: 00000000773a69f9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000e78c9bed (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7637:
 #0: 000000003d4f338c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000de3e0ce9 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7638:
 #0: 0000000016d0ea06 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000493f990b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7639:
 #0: 0000000092f18b36 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000b0df7e2f (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7640:
 #0: 000000003672360d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000bba5c0a2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
3 locks held by kworker/u4:15/27613:
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 00000000c69ced1f ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0x87e/0x1750 kernel/workqueue.c:2124
 #1: 000000002cfc03e6 ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128
 #2: 00000000f569a491 (&buf->lock){+.+.}, at: flush_to_ldisc+0x3d/0x390 drivers/tty/tty_buffer.c:500
2 locks held by getty/25533:
 #0: 000000009315d2c3 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 0000000096a85e3e (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
3 locks held by syz-executor.0/31679:
2 locks held by syz-executor.5/31892:
 #0: 00000000773a69f9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000f569a491 (&buf->lock){+.+.}, at: tty_buffer_lock_exclusive+0x30/0x40 drivers/tty/tty_buffer.c:61
2 locks held by syz-executor.3/31896:
 #0: 00000000773a69f9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000f569a491 (&buf->lock){+.+.}, at: tty_buffer_lock_exclusive+0x30/0x40 drivers/tty/tty_buffer.c:61

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

NMI backtrace for cpu 1
CPU: 1 PID: 1068 Comm: khungtaskd Not tainted 4.19.92-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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 31679 Comm: syz-executor.0 Not tainted 4.19.92-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__lock_is_held+0xb1/0x140 kernel/locking/lockdep.c:3723
Code: 84 c0 74 08 3c 03 0f 8e 92 00 00 00 44 39 b3 78 08 00 00 7e 6a 48 8b 4d d0 49 63 c6 4c 89 e6 48 8d 04 80 4c 8d 3c c1 4c 89 ff <e8> 1a f9 ff ff 85 c0 74 c4 83 7d c4 ff b8 01 00 00 00 74 43 49 8d
RSP: 0018:ffff88806f7ef630 EFLAGS: 00000006
RAX: 0000000000000000 RBX: ffff88809fb302c0 RCX: ffff88809fb30b40
RDX: 1ffff11013f66167 RSI: ffff8880ae82c258 RDI: ffff88809fb30b40
RBP: ffff88806f7ef670 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8a0b2010 R11: 0000000000000001 R12: ffff8880ae82c258
R13: ffffed1013f66167 R14: 0000000000000000 R15: ffff88809fb30b40
FS:  00007f5ae35bd700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c42be1f000 CR3: 000000006b913000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 lock_is_held_type+0x110/0x210 kernel/locking/lockdep.c:3941
 lock_is_held include/linux/lockdep.h:344 [inline]
 rq_clock_task kernel/sched/sched.h:1000 [inline]
 update_curr+0x296/0x8a0 kernel/sched/fair.c:804
 pick_next_task_fair+0x6bf/0x1580 kernel/sched/fair.c:6698
 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: 0033:0x45a9e9
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:00007f5ae35bcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a9e9
RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5ae35bd6d4
R13: 00000000004c5db9 R14: 00000000004dc4d8 R15: 00000000ffffffff

Crashes (2):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-19 2019/12/31 17:02 linux-4.19.y c7ecf3e3a71c 25a0186e .config log report
ci2-linux-4-19 2019/12/20 14:50 linux-4.19.y 7d120bf21c05 34011c05 .config log report