syzbot


INFO: task hung in flush_to_ldisc (2)

Status: auto-closed as invalid on 2020/12/28 13:53
Reported-by: syzbot+9b0666485cd08d649aa8@syzkaller.appspotmail.com
First crash: 829d, last: 829d
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 876d 876d 0/1 auto-closed as invalid on 2020/11/11 17:44
upstream INFO: task hung in flush_to_ldisc (2) 1 607d 607d 0/24 auto-closed as invalid on 2021/06/09 11:04
linux-4.19 INFO: task hung in flush_to_ldisc 10 1025d 1088d 0/1 auto-closed as invalid on 2020/06/15 14:09
upstream INFO: task hung in flush_to_ldisc C inconclusive done 15 1028d 1098d 17/24 fixed on 2020/11/16 12:12
linux-4.14 INFO: task hung in flush_to_ldisc (3) 1 638d 638d 0/1 auto-closed as invalid on 2021/07/07 16:40
upstream INFO: task hung in flush_to_ldisc (3) C inconclusive 3 307d 496d 0/24 closed as invalid on 2022/02/08 10:26
linux-4.19 INFO: task hung in flush_to_ldisc (3) 1 590d 590d 0/1 auto-closed as invalid on 2021/08/25 00:39
linux-4.14 INFO: task hung in flush_to_ldisc 8 1018d 1088d 0/1 auto-closed as invalid on 2020/06/23 11:01

Sample crash report:
Bluetooth: hci3 command 0x0406 tx timeout
Bluetooth: hci0 command 0x0406 tx timeout
INFO: task kworker/u4:6:7800 blocked for more than 140 seconds.
      Not tainted 4.14.195-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:6    D26344  7800      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:20811 blocked for more than 140 seconds.
      Not tainted 4.14.195-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
agetty          D27464 20811      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:1731
 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+0x98/0x6f0 drivers/tty/tty_jobctrl.c:266
 disassociate_ctty+0x71/0x90 drivers/tty/tty_jobctrl.c:260
 do_exit+0x1613/0x27f0 kernel/exit.c:863
 do_group_exit+0x100/0x2e0 kernel/exit.c:962
 SYSC_exit_group kernel/exit.c:973 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:971
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7fd9de101618
RSP: 002b:00007fffed507aa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fd9de101618
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 00007fd9de3de8e0 R08: 00000000000000e7 R09: ffffffffffffff98
R10: 00007fffed507a28 R11: 0000000000000246 R12: 00007fd9de3de8e0
R13: 00007fd9de3e3c20 R14: 0000000000000001 R15: 000000000000000a
INFO: task syz-executor.1:21311 blocked for more than 140 seconds.
      Not tainted 4.14.195-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D28360 21311   6366 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/0x414 drivers/tty/vt/selection.c:373
 tioclinux+0xfd/0x490 drivers/tty/vt/vt.c:2713
 vt_ioctl+0x12fb/0x1ea0 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: 0033:0x45d5b9
RSP: 002b:00007f4fb462ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000019380 RCX: 000000000045d5b9
RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000009
RBP: 000000000118d160 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118d12c
R13: 00007ffdb8276fcf R14: 00007f4fb462b9c0 R15: 000000000118d12c

Showing all locks held in the system:
1 lock held by khungtaskd/1067:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff814777f4>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/6019:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8193b49b>] __fdget_pos+0x1fb/0x2b0 fs/file.c:769
3 locks held by kworker/u4:6/7800:
 #0:  ("events_unbound"){+.+.}, at: [<ffffffff813ba640>] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2087
 #1:  ((&buf->work)){+.+.}, at: [<ffffffff813ba676>] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2091
 #2:  (&buf->lock){+.+.}, at: [<ffffffff83440a25>] flush_to_ldisc+0x35/0x3f0 drivers/tty/tty_buffer.c:499
1 lock held by syz-executor.1/17617:
 #0:  (&tty->legacy_mutex){+.+.}, at: [<ffffffff8344460f>] tty_lock+0x5f/0x70 drivers/tty/tty_mutex.c:19
2 locks held by agetty/20811:
 #0:  (&tty->legacy_mutex){+.+.}, at: [<ffffffff8344460f>] tty_lock+0x5f/0x70 drivers/tty/tty_mutex.c:19
 #1:  (&tty->ldisc_sem){++++}, at: [<ffffffff8343ecad>] __tty_ldisc_lock drivers/tty/tty_ldisc.c:332 [inline]
 #1:  (&tty->ldisc_sem){++++}, at: [<ffffffff8343ecad>] tty_ldisc_lock+0x4d/0x80 drivers/tty/tty_ldisc.c:356
2 locks held by syz-executor.0/21252:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff8343e182>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&buf->lock){+.+.}, at: [<ffffffff83463f9e>] paste_selection+0x10e/0x414 drivers/tty/vt/selection.c:373
2 locks held by syz-executor.1/21311:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff8343e182>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&buf->lock){+.+.}, at: [<ffffffff83463f9e>] paste_selection+0x10e/0x414 drivers/tty/vt/selection.c:373

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

NMI backtrace for cpu 0
CPU: 0 PID: 1067 Comm: khungtaskd Not tainted 4.14.195-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+0x1b2/0x283 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x13a/0x17f 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 skipped: idling at pc 0xffffffff86547e8e

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/08/30 13:53 linux-4.14.y d7e78d08fa77 d5a3ae1f .config log report
* Struck through repros no longer work on HEAD.