syzbot


INFO: task hung in n_tty_read

Status: auto-closed as invalid on 2020/05/09 10:39
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 976d, last: 922d
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 905d 945d 0/1 auto-closed as invalid on 2020/06/25 03:18
android-44 INFO: task hung in n_tty_read 1 1056d 1056d 0/2 auto-closed as invalid on 2020/01/25 18:14
upstream INFO: task hung in n_tty_read (2) C error 1 500d 496d 0/23 upstream: reported C repro on 2021/04/09 23:49
linux-4.14 INFO: task hung in n_tty_read (2) 1 480d 480d 0/1 auto-closed as invalid on 2021/08/24 04:16
linux-4.19 INFO: task hung in n_tty_read 2 961d 972d 0/1 auto-closed as invalid on 2020/04/29 17:03

Sample crash report:
INFO: task login:8797 blocked for more than 143 seconds.
      Not tainted 5.5.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
login           D23376  8797      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: 0033:0x7f314822e310
Code: Bad RIP value.
RSP: 002b:00007ffd9e404088 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f314822e310
RDX: 00000000000001ff RSI: 00007ffd9e4042f0 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007f3148b11700 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd9e4042f0
R13: 0000000000000000 R14: 0000000000000001 R15: 000000000060b798
INFO: task kworker/u4:6:9111 blocked for more than 143 seconds.
      Not tainted 5.5.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:6    D24616  9111      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
 process_scheduled_works kernel/workqueue.c:2326 [inline]
 worker_thread+0xe77/0x1630 kernel/workqueue.c:2415
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Showing all locks held in the system:
1 lock held by khungtaskd/1126:
 #0: ffffffff892d98c8 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 include/linux/rcupdate.h:207
1 lock held by rsyslogd/8707:
 #0: ffff88809a3723e0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x279/0x310 fs/file.c:821
2 locks held by login/8797:
 #0: ffff8880a3468090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffffc900017a72e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156
2 locks held by getty/8798:
 #0: ffff88809dd64090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffffc9000181b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156
2 locks held by getty/8799:
 #0: ffff88809e084090 (&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/8800:
 #0: ffff888091b15090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffffc900017db2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156
2 locks held by getty/8801:
 #0: ffff88809dd65090 (&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/8802:
 #0: ffff888091a2c090 (&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/8803:
 #0: ffff888092909090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffffc9000178b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x22f/0x1bc0 drivers/tty/n_tty.c:2156
3 locks held by kworker/u4:6/9111:
 #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: ffffc900047efd78 ((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
2 locks held by syz-executor.2/13521:
 #0: ffff8880a3468090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffff8880aa5be0a8 (&buf->lock){+.+.}, at: tty_buffer_lock_exclusive+0x33/0x40 drivers/tty/tty_buffer.c:61

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

NMI backtrace for cpu 1
CPU: 1 PID: 1126 Comm: khungtaskd Not tainted 5.5.0-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: 13521 Comm: syz-executor.2 Not tainted 5.5.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:match_held_lock+0x64/0x270 kernel/locking/lockdep.c:4016
Code: 4c 89 f2 41 be 01 00 00 00 4c 39 2b 0f 84 fe 00 00 00 49 8d 74 24 20 49 89 f7 49 c1 ef 03 41 8a 04 17 84 c0 0f 85 42 01 00 00 <81> 3e 00 00 10 00 0f 82 d7 00 00 00 49 8d 5d 08 48 89 d8 48 c1 e8
RSP: 0018:ffffc9000d3ff7b0 EFLAGS: 00000046
RAX: 1ffff1100c581900 RBX: ffff888062c0ce38 RCX: ffffffff8163e887
RDX: dffffc0000000000 RSI: ffff888062c0ce48 RDI: ffff888062c0ce28
RBP: ffffc9000d3ff7e0 R08: dffffc0000000000 R09: ffffed1015d47004
R10: ffffed1015d47004 R11: 0000000000000000 R12: ffff888062c0ce28
R13: ffffffff892e24e8 R14: 0000000000000001 R15: 1ffff1100c5819c9
FS:  00007fc9a4547700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30930000 CR3: 000000007aadb000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
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]
 task_css include/linux/cgroup.h:491 [inline]
 task_ca kernel/sched/cpuacct.c:43 [inline]
 cpuacct_charge+0x104/0x2b0 kernel/sched/cpuacct.c:349
 cgroup_account_cputime include/linux/cgroup.h:773 [inline]
 update_curr+0x515/0xd00 kernel/sched/fair.c:860
 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: 0033:0x45b399
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:00007fc9a4546c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc9a45476d4 RCX: 000000000045b399
RDX: 0000000020000000 RSI: 000000000000541c RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000056c R14: 00000000004c6b4d R15: 000000000075bf2c

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce-smack-root 2020/02/09 10:38 upstream fdfa3a6778b1 6ece2ea5 .config log report
ci-upstream-kasan-gce-selinux-root 2020/01/16 00:18 upstream 51d69817519f f9b69507 .config log report
ci-upstream-linux-next-kasan-gce-root 2019/12/17 04:51 linux-next fca4fe890ea0 d13d7958 .config log report