INFO: task hung in tty_ldisc_hangup (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c7150cd2 Linux 4.14.225
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1759ff76d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=112b229d8a53892f
dashboard link: https://syzkaller.appspot.com/bug?extid=190d63efd4dca5610c33

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+190d63...@syzkaller.appspotmail.com

tmpfs: No value for mount option '00000000000000060928'
tmpfs: No value for mount option '00000000000000060928'
tmpfs: No value for mount option '00000000000000060928'
Bluetooth: hci4 command 0x0406 tx timeout
INFO: task login:3342 blocked for more than 140 seconds.
Not tainted 4.14.225-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
login D28072 3342 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: 0033:0x7fea5ffc6618
RSP: 002b:00007ffc90a1d728 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007fea5ffc6618
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 0000000000000000 R08: 00000000000000e7 R09: ffffffffffffff98
R10: 000000000000037b R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000001 R14: 00007ffc90a1e2f8 R15: 00005604cbb2bb18
INFO: task syz-executor.3:6554 blocked for more than 140 seconds.
Not tainted 4.14.225-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D29288 6554 2211 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:00007f85a77b6188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056c0b0 RCX: 0000000000465f69
RDX: 0000000020000100 RSI: 000000000000541c RDI: 0000000000000004
RBP: 00000000004bfa8f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0b0
R13: 00007ffc42820e0f R14: 00007f85a77b6300 R15: 0000000000022000
INFO: task syz-executor.1:6555 blocked for more than 140 seconds.
Not tainted 4.14.225-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D28584 6555 8000 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:00007fd8c8ab8188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000465f69
RDX: 0000000020000100 RSI: 000000000000541c RDI: 0000000000000004
RBP: 00000000004bfa8f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008
R13: 00007fffd99354cf R14: 00007fd8c8ab8300 R15: 0000000000022000
INFO: task syz-executor.2:6561 blocked for more than 140 seconds.
Not tainted 4.14.225-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D28200 6561 7998 0x00000000
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:00007f5036a61188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465f69
RDX: 0000000020000100 RSI: 000000000000541c RDI: 0000000000000004
RBP: 00000000004bfa8f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007fff4e8de99f R14: 00007f5036a61300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1527:
#0: (tasklist_lock){.+.+}, at: [<ffffffff86ff2967>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
2 locks held by login/3342:
#0: (&tty->legacy_mutex){+.+.}, at: [<ffffffff8353d37f>] tty_lock+0x5f/0x70 drivers/tty/tty_mutex.c:19
#1: (&tty->ldisc_sem){++++}, at: [<ffffffff83537a2d>] __tty_ldisc_lock drivers/tty/tty_ldisc.c:332 [inline]
#1: (&tty->ldisc_sem){++++}, at: [<ffffffff83537a2d>] tty_ldisc_lock+0x4d/0x80 drivers/tty/tty_ldisc.c:356
2 locks held by syz-executor.2/6525:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff83536f02>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&buf->lock){+.+.}, at: [<ffffffff8355c22e>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373
2 locks held by syz-executor.3/6554:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff83536f02>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&buf->lock){+.+.}, at: [<ffffffff8355c22e>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373
2 locks held by syz-executor.1/6555:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff83536f02>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&buf->lock){+.+.}, at: [<ffffffff8355c22e>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373
2 locks held by syz-executor.2/6561:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff83536f02>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&buf->lock){+.+.}, at: [<ffffffff8355c22e>] paste_selection+0x10e/0x420 drivers/tty/vt/selection.c:373

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

NMI backtrace for cpu 1
CPU: 1 PID: 1527 Comm: khungtaskd Not tainted 4.14.225-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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4626 Comm: systemd-journal Not tainted 4.14.225-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880a0e5a1c0 task.stack: ffff8880a0e60000
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:60
RSP: 0018:ffff8880a0e678c8 EFLAGS: 00000297
RAX: ffff8880a0e5a1c0 RBX: ffff8880a0e5a1c0 RCX: 1ffffffff127a03c
RDX: 0000000000000000 RSI: ffffffff87ccd680 RDI: ffffffff87ccd6c0
RBP: ffffffff87ccd6c0 R08: ffffffff8b9c2788 R09: 0000000000000000
R10: ffff88804860b73f R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff87ccd680 R14: ffff8880b580d5c0 R15: ffff88808e78be30
FS: 00007f1f7b2ee8c0(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1f78b65000 CR3: 00000000a0f6a000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
check_preemption_disabled+0x35/0x240 lib/smp_processor_id.c:52
rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:360 [inline]
rcu_is_watching+0x11/0xb0 kernel/rcu/tree.c:1130
rcu_read_lock_held+0xba/0x110 kernel/rcu/update.c:328
hlist_bl_first_rcu include/linux/rculist_bl.h:24 [inline]
__d_lookup_rcu+0x35d/0x640 fs/dcache.c:2203
lookup_fast+0xf0/0xe30 fs/namei.c:1595
walk_component+0xc0/0xbc0 fs/namei.c:1821
link_path_walk+0x823/0x10a0 fs/namei.c:2154
path_parentat+0x41/0x120 fs/namei.c:2398
filename_parentat+0x176/0x520 fs/namei.c:2420
filename_create+0x8a/0x3f0 fs/namei.c:3657
user_path_create fs/namei.c:3732 [inline]
SYSC_mkdirat fs/namei.c:3864 [inline]
SyS_mkdirat+0x95/0x270 fs/namei.c:3856
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f1f7a5aa687
RSP: 002b:00007ffc41946318 EFLAGS: 00000293 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007ffc41949230 RCX: 00007f1f7a5aa687
RDX: 00007f1f7b01ba00 RSI: 00000000000001ed RDI: 000056229f6c98a0
RBP: 00007ffc41946350 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffc41949230 R15: 00007ffc41946840
Code: ff ff 48 89 df e8 61 88 29 00 e9 9f fe ff ff 4c 89 e7 e8 54 88 29 00 e9 2c fe ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <65> 48 8b 04 25 80 df 01 00 48 85 c0 74 1a 65 8b 15 cb bd ac 7e


---
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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.