INFO: task hung in blkdev_put

[syzbot]

Hello,

syzkaller hit the following crash on
ad4dac17f9d563b9e34aab78a34293b10993e9b5
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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


Buffer I/O error on dev loop0, logical block 8, async page read
INFO: task blkid:16495 blocked for more than 120 seconds.
Not tainted 4.15.0-rc2-next-20171208+ #63
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D21344 16495 3125 0x80000006
Call Trace:
context_switch kernel/sched/core.c:2800 [inline]
__schedule+0x8eb/0x2060 kernel/sched/core.c:3376
schedule+0xf5/0x430 kernel/sched/core.c:3435
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3493
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_put+0x2a/0x4f0 fs/block_dev.c:1793
blkdev_close+0x91/0xc0 fs/block_dev.c:1842
__fput+0x333/0x7f0 fs/file_table.c:210
____fput+0x15/0x20 fs/file_table.c:244
task_work_run+0x199/0x270 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x9bb/0x1ae0 kernel/exit.c:869
do_group_exit+0x149/0x400 kernel/exit.c:972
get_signal+0x73f/0x16c0 kernel/signal.c:2337
do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:161
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
entry_SYSCALL_64_fastpath+0x94/0x96
RIP: 0033:0x7f2117ef9310
RSP: 002b:00007ffeedf28478 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffffb RBX: 0000000000002000 RCX: 00007f2117ef9310
RDX: 0000000000000561 RSI: 0000000000ea2a58 RDI: 0000000000000003
RBP: 0000000000ea2a30 R08: 0000000000000018 R09: 0000000000168000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000ea1030
R13: 0000000000000561 R14: 0000000000ea1080 R15: 0000000000ea2a48

Showing all locks held in the system:
2 locks held by khungtaskd/672:
#0: (rcu_read_lock){....}, at: [<00000000166545b0>]
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: (rcu_read_lock){....}, at: [<00000000166545b0>] watchdog+0x1c5/0xd60
kernel/hung_task.c:249
#1: (tasklist_lock){.+.+}, at: [<00000000327f4dad>]
debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
1 lock held by rsyslogd/2993:
#0: (&f->f_pos_lock){+.+.}, at: [<000000006eb70b1d>]
__fdget_pos+0x131/0x1a0 fs/file.c:765
2 locks held by getty/3115:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3116:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3117:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3118:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3119:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3120:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3121:
#0: (&tty->ldisc_sem){++++}, at: [<0000000059fa20b1>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007035e50d>]
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
3 locks held by kworker/u4:9/4216:
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
__write_once_size include/linux/compiler.h:212 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
set_work_data kernel/workqueue.c:619 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: ((wq_completion)"writeback"){+.+.}, at: [<0000000064bfb8f2>]
process_one_work+0xad4/0x1bc0 kernel/workqueue.c:2084
#1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at:
[<000000009ce31f83>] process_one_work+0xb2f/0x1bc0 kernel/workqueue.c:2088
#2: (&type->s_umount_key#25){++++}, at: [<000000008ac62721>]
trylock_super+0x20/0x100 fs/super.c:395
1 lock held by blkid/16495:
#0: (&bdev->bd_mutex){+.+.}, at: [<000000007747ddd3>]
blkdev_put+0x2a/0x4f0 fs/block_dev.c:1793
1 lock held by syz-executor3/16557:
#0: (&bdev->bd_mutex){+.+.}, at: [<000000007747ddd3>]
blkdev_put+0x2a/0x4f0 fs/block_dev.c:1793
1 lock held by syz-executor7/16620:
#0: (&bdev->bd_mutex){+.+.}, at: [<00000000f5d98222>]
iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145
1 lock held by syz-executor7/16640:
#0: (&bdev->bd_mutex){+.+.}, at: [<00000000f5d98222>]
iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145

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

NMI backtrace for cpu 1
CPU: 1 PID: 672 Comm: khungtaskd Not tainted 4.15.0-rc2-next-20171208+ #63
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+0x194/0x257 lib/dump_stack.c:53
nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x122/0x180 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:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0x90c/0xd60 kernel/hung_task.c:249
kthread+0x37a/0x440 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc2-next-20171208+ #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:183 [inline]
RIP: 0010:atomic_read arch/x86/include/asm/atomic.h:27 [inline]
RIP: 0010:nr_iowait_cpu+0xbc/0x120 kernel/sched/core.c:2902
RSP: 0018:ffff8801db207c58 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8801db22c900 RCX: ffffffff8163cfdd
RDX: dffffc0000000000 RSI: ffff8801db223540 RDI: ffff8801db207c80
RBP: ffff8801db207cd8 R08: ffff88021fff801c R09: ffff88021fff8008
R10: ffff88021fff8010 R11: ffff88021fff801d R12: 1ffff1003b640f8c
R13: 0000000000000000 R14: ffff8801db2235c8 R15: ffff8801db223540
FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000147b000 CR3: 00000001cc504000 CR4: 00000000001406f0
DR0: 0000000020001000 DR1: 0000000020001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
update_ts_time_stats+0xee/0x1c0 kernel/time/tick-sched.c:504
tick_nohz_stop_idle kernel/time/tick-sched.c:518 [inline]
tick_nohz_irq_enter kernel/time/tick-sched.c:1104 [inline]
tick_irq_enter+0x262/0x390 kernel/time/tick-sched.c:1123
irq_enter+0xbd/0xe0 kernel/softirq.c:346
scheduler_ipi+0x246/0x830 kernel/sched/core.c:1794
smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277
reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:944
</IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffffffff86207d08 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02
RAX: dffffc0000000000 RBX: 1ffffffff0c40fa4 RCX: 0000000000000000
RDX: 1ffffffff0c5975c RSI: 0000000000000001 RDI: ffffffff862cbae0
RBP: ffffffff86207d08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff86207dc0 R14: ffffffff869efaa0 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
default_idle+0xbf/0x430 arch/x86/kernel/process.c:355
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
default_idle_call+0x36/0x90 kernel/sched/idle.c:98
cpuidle_idle_call kernel/sched/idle.c:156 [inline]
do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351
rest_init+0xed/0xf0 init/main.c:436
start_kernel+0x729/0x74f init/main.c:717
x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237
Code: 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 5d 48
8d 7d a8 48 ba 00 00 00 00 00 fc ff df 48 63 83 28 0a 00 00 <48> 89 f9 48
c1 e9 03 0f b6 14 11 84 d2 74 05 80 fa 03 7e 26 48


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.
Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>

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[Dmitry Vyukov]

On Sun, Dec 10, 2017 at 2:38 PM, syzbot
<bot+a444b4083d33277c6e...@syzkaller.appspotmail.com>
wrote:

+loop maintainers

#syz dup: INFO: task hung in lo_ioctl

> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzk...@googlegroups.com.
> Please credit me with: Reported-by: syzbot <syzk...@googlegroups.com>
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is merged into any tree, reply to this email with:
> #syz fix: exact-commit-title
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line in the email body.
>

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[Tetsuo Handa]

On 2017/12/13 1:45, Dmitry Vyukov wrote:
> +loop maintainers
>
> #syz dup: INFO: task hung in lo_ioctl

https://syzkaller.appspot.com/text?tag=CrashLog&x=14a09f95400000 has
"getblk(): executed=9 bh_count=0 bh_state=0" line.

#syz undup

[Tetsuo Handa]

Merging into not-yet-fixed this one.

#syz dup: INFO: task hung in generic_file_write_iter