Message-ID: <CACT4Y+YLFp4OXRyroL8coE5Mw6yMdbajKPeu8kzkHunVGypx0Q@mail.gmail.com>
Date:   Thu, 1 Nov 2018 12:05:45 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+6339eda9cb4ebbc4c37b@...kaller.appspotmail.com>
Cc:     linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        syzkaller-bugs@...glegroups.com
Subject: Re: INFO: task hung in fuse_sb_destroy

On Thu, Nov 1, 2018 at 11:49 AM, syzbot
<syzbot+6339eda9cb4ebbc4c37b@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    59fc453b21f7 Merge branch 'akpm' (patches from Andrew)
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15fb2447400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ea045471e4c756e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=6339eda9cb4ebbc4c37b
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=178a105d400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16651133400000


I can easily reproduce this.

The repro gives me a task hanged at:

# cat /proc/7563/task/*/stack
[<0>] fuse_wait_aborted+0x20b/0x320
[<0>] fuse_sb_destroy+0xe2/0x1d0
[<0>] fuse_kill_sb_anon+0x15/0x20
[<0>] deactivate_locked_super+0x97/0x100
[<0>] deactivate_super+0x2bb/0x320
[<0>] cleanup_mnt+0xbf/0x160
[<0>] __cleanup_mnt+0x16/0x20
[<0>] task_work_run+0x1e8/0x2a0
[<0>] exit_to_usermode_loop+0x318/0x380
[<0>] do_syscall_64+0x6be/0x820
[<0>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[<0>] 0xffffffffffffffff

I double checked that writing to /sys/fs/fuse/connections/44/abort did
not help (the only entry in fuse/connections). Wrote multiple times,
and tried to kill the task, nothing helps.



> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6339eda9cb4ebbc4c37b@...kaller.appspotmail.com
>
> INFO: task syz-executor221:17414 blocked for more than 140 seconds.
>       Not tainted 4.19.0+ #313
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> syz-executor221 D23048 17414   5652 0x00000004
> Call Trace:
>  context_switch kernel/sched/core.c:2831 [inline]
>  __schedule+0x8cf/0x21d0 kernel/sched/core.c:3472
>  schedule+0xfe/0x460 kernel/sched/core.c:3516
>  fuse_wait_aborted+0x20b/0x320 fs/fuse/dev.c:2155
>  fuse_sb_destroy+0xe2/0x1d0 fs/fuse/inode.c:1224
>  fuse_kill_sb_anon+0x15/0x20 fs/fuse/inode.c:1234
>  deactivate_locked_super+0x97/0x100 fs/super.c:329
>  deactivate_super+0x2bb/0x320 fs/super.c:360
>  cleanup_mnt+0xbf/0x160 fs/namespace.c:1098
>  __cleanup_mnt+0x16/0x20 fs/namespace.c:1105
>  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>  exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>  do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446689
> Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f621e979da8 EFLAGS: 00000293 ORIG_RAX: 00000000000000a6
> RAX: 0000000000000000 RBX: 00000000006dbc28 RCX: 0000000000446689
> RDX: 0000000000446689 RSI: 000000000000000a RDI: 0000000020000180
> RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000293 R12: 00000000006dbc2c
> R13: 0030656c69662f2e R14: 65646f6d746f6f72 R15: 0000000000000000
>
> Showing all locks held in the system:
> 1 lock held by khungtaskd/1009:
>  #0: 0000000095618e4f (rcu_read_lock){....}, at:
> debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4379
> 5 locks held by rsyslogd/5530:
>  #0: 0000000028bad575 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1bb/0x200
> fs/file.c:766
>  #1: 00000000e31592cd (&rq->lock){-.-.}, at: rq_lock
> kernel/sched/sched.h:1126 [inline]
>  #1: 00000000e31592cd (&rq->lock){-.-.}, at: __schedule+0x236/0x21d0
> kernel/sched/core.c:3410
>  #2: 0000000095618e4f (rcu_read_lock){....}, at: trace_sched_stat_runtime
> include/trace/events/sched.h:418 [inline]
>  #2: 0000000095618e4f (rcu_read_lock){....}, at: update_curr+0x383/0xbd0
> kernel/sched/fair.c:830
>  #3: 00000000e31592cd (&rq->lock){-.-.}, at: rq_lock
> kernel/sched/sched.h:1126 [inline]
>  #3: 00000000e31592cd (&rq->lock){-.-.}, at: ttwu_queue
> kernel/sched/core.c:1845 [inline]
>  #3: 00000000e31592cd (&rq->lock){-.-.}, at: try_to_wake_up+0x9f6/0x1490
> kernel/sched/core.c:2057
>  #4: 0000000095618e4f (rcu_read_lock){....}, at: trace_sched_stat_runtime
> include/trace/events/sched.h:418 [inline]
>  #4: 0000000095618e4f (rcu_read_lock){....}, at: update_curr+0x383/0xbd0
> kernel/sched/fair.c:830
> 2 locks held by getty/5620:
>  #0: 00000000492d5ad8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 0000000088c4d769 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5621:
>  #0: 00000000ed56cf3c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000a8112d49 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5622:
>  #0: 00000000858703c2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000b20ff0f8 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5623:
>  #0: 00000000a0163126 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000cb4be99e (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5624:
>  #0: 000000006eab39a0 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000341e7ea5 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5625:
>  #0: 00000000e1bb9e75 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000e6c38e03 (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by getty/5626:
>  #0: 00000000437eab2d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40
> drivers/tty/tty_ldsem.c:353
>  #1: 00000000031acd5c (&ldata->atomic_read_lock){+.+.}, at:
> n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
> 2 locks held by kworker/1:0/5718:
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at: __write_once_size
> include/linux/compiler.h:206 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at: arch_atomic64_set
> arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at: atomic64_set
> include/asm-generic/atomic-instrumented.h:40 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at: atomic_long_set
> include/asm-generic/atomic-long.h:59 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at: set_work_data
> kernel/workqueue.c:617 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at:
> set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
>  #0: 0000000003693dce ((wq_completion)"rcu_gp"){+.+.}, at:
> process_one_work+0xb43/0x1c40 kernel/workqueue.c:2124
>  #1: 00000000fdcab2d3 ((work_completion)(&rew.rew_work)){+.+.}, at:
> process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128
> 1 lock held by syz-executor221/17414:
>  #0: 000000003df3056e (&type->s_umount_key#39){+.+.}, at:
> deactivate_super+0x2b3/0x320 fs/super.c:359
> 1 lock held by syz-executor221/18647:
>  #0: 00000000dd0c9ec5 (rcu_state.exp_mutex){+.+.}, at: exp_funnel_lock
> kernel/rcu/tree_exp.h:296 [inline]
>  #0: 00000000dd0c9ec5 (rcu_state.exp_mutex){+.+.}, at:
> _synchronize_rcu_expedited.constprop.58+0x7c7/0x9d0
> kernel/rcu/tree_exp.h:620
> 1 lock held by syz-executor221/18653:
>  #0: 00000000dd0c9ec5 (rcu_state.exp_mutex){+.+.}, at: exp_funnel_lock
> kernel/rcu/tree_exp.h:328 [inline]
>  #0: 00000000dd0c9ec5 (rcu_state.exp_mutex){+.+.}, at:
> _synchronize_rcu_expedited.constprop.58+0x7af/0x9d0
> kernel/rcu/tree_exp.h:620
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 1009 Comm: khungtaskd Not tainted 4.19.0+ #313
> 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+0x244/0x39d lib/dump_stack.c:113
>  nmi_cpu_backtrace.cold.2+0x5c/0xa1 lib/nmi_backtrace.c:101
>  nmi_trigger_cpumask_backtrace+0x1e8/0x22a 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:144 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
>  watchdog+0xb51/0x1060 kernel/hung_task.c:289
>  kthread+0x35a/0x440 kernel/kthread.c:246
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 18647 Comm: syz-executor221 Not tainted 4.19.0+ #313
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:outb arch/x86/include/asm/io.h:334 [inline]
> RIP: 0010:io_serial_out+0x73/0x90 drivers/tty/serial/8250/8250_port.c:455
> Code: 00 49 8d 7c 24 38 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03
> d3 e3 80 3c 02 00 75 19 41 03 5c 24 38 44 89 e8 89 da ee <5b> 41 5c 41 5d 5d
> c3 e8 e1 66 e0 fd eb c0 e8 3a 67 e0 fd eb e0 0f
> RSP: 0018:ffff8801cc666f90 EFLAGS: 00000006
> RAX: 0000000000000000 RBX: 00000000000003f9 RCX: 0000000000000000
> RDX: 00000000000003f9 RSI: ffffffff83e257a6 RDI: ffffffff8bae5158
> RBP: ffff8801cc666fa8 R08: ffff8801bf0b0600 R09: ffffed00398ccde3
> R10: ffffed00398ccde3 R11: 0000000000000003 R12: ffffffff8bae5120
> R13: 0000000000000000 R14: 0000000000000001 R15: ffffffff8bae5168
> FS:  00007f621e97a700(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f313a840000 CR3: 00000001c3654000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  serial_port_out include/linux/serial_core.h:276 [inline]
>  serial8250_console_write+0x34b/0xb10
> drivers/tty/serial/8250/8250_port.c:3276
>  univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:586
>  call_console_drivers kernel/printk/printk.c:1728 [inline]
>  console_unlock+0xb1f/0x1190 kernel/printk/printk.c:2414
>  vprintk_emit+0x391/0x990 kernel/printk/printk.c:1922
>  vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
>  vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
>  printk+0xa7/0xcf kernel/printk/printk.c:1997
>  kobject_cleanup lib/kobject.c:638 [inline]
>  kobject_release lib/kobject.c:691 [inline]
>  kref_put include/linux/kref.h:70 [inline]
>  kobject_put.cold.9+0x83/0x2e4 lib/kobject.c:708
>  put_device drivers/base/core.c:2024 [inline]
>  device_unregister+0x28/0x30 drivers/base/core.c:2114
>  bdi_unregister+0x5ed/0x880 mm/backing-dev.c:948
>  release_bdi mm/backing-dev.c:964 [inline]
>  kref_put include/linux/kref.h:70 [inline]
>  bdi_put+0x153/0x180 mm/backing-dev.c:973
>  generic_shutdown_super+0x3c8/0x530 fs/super.c:470
>  kill_anon_super+0x3e/0x60 fs/super.c:1032
>  fuse_kill_sb_anon+0x1d/0x20 fs/fuse/inode.c:1235
>  deactivate_locked_super+0x97/0x100 fs/super.c:329
>  deactivate_super+0x2bb/0x320 fs/super.c:360
>  cleanup_mnt+0xbf/0x160 fs/namespace.c:1098
>  __cleanup_mnt+0x16/0x20 fs/namespace.c:1105
>  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>  get_signal+0x1558/0x1980 kernel/signal.c:2347
>  do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
>  exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>  do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446689
> Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f621e979da8 EFLAGS: 00000293 ORIG_RAX: 00000000000000a6
> RAX: 0000000000000000 RBX: 00000000006dbc28 RCX: 0000000000446689
> RDX: 0000000000446689 RSI: 000000000000000a RDI: 0000000020000180
> RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000293 R12: 00000000006dbc2c
> R13: 0030656c69662f2e R14: 65646f6d746f6f72 R15: 0000000000000000
> INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.274
> msecs
> kobject: '0:31' (0000000050d00699): fill_kobj_path: path =
> '/devices/virtual/bdi/0:31'
> kobject: '0:32' (00000000d2d168d9): kobject_cleanup, parent           (null)
> kobject: '0:31' (0000000050d00699): kobject_cleanup, parent           (null)
> kobject: '0:32' (00000000d2d168d9): calling ktype release
> kobject: '0:33' (00000000d76406a3): kobject_cleanup, parent           (null)
> kobject: '0:28' (000000002da84317): calling ktype release
> kobject: '0:29' (00000000e2434e73): kobject_cleanup, parent           (null)
> kobject: '0:32': free name
> kobject: '0:33' (00000000d76406a3): calling ktype release
> kobject: '0:33': free name
> kobject: '0:29' (00000000e2434e73): calling ktype release
> kobject: '0:28': free name
> kobject: '0:29': free name
> kobject: '0:31' (0000000050d00699): calling ktype release
> kobject: '0:28' (0000000080474e07): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:29' (0000000051f8f0a5): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:28' (0000000080474e07): kobject_uevent_env
> kobject: '0:32' (0000000075558c25): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:33' (00000000c8dd3226): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:29' (0000000051f8f0a5): kobject_uevent_env
> kobject: '0:33' (00000000c8dd3226): kobject_uevent_env
> kobject: '0:31': free name
> kobject: '0:28' (0000000080474e07): fill_kobj_path: path =
> '/devices/virtual/bdi/0:28'
> kobject: '0:29' (0000000051f8f0a5): fill_kobj_path: path =
> '/devices/virtual/bdi/0:29'
> kobject: '0:34' (000000008aa55f96): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:33' (00000000c8dd3226): fill_kobj_path: path =
> '/devices/virtual/bdi/0:33'
> kobject: '0:31' (000000008e78fdc7): kobject_add_internal: parent: 'bdi',
> set: 'devices'
> kobject: '0:32' (0000000075558c25): kobject_uevent_env
> kobject: '0:34' (000000008aa55f96): kobject_uevent_env
> kobject: '0:32' (0000000075558c25): fill_kobj_path: path =
> '/devices/virtual/bdi/0:32'
> kobject: '0:34' (000000008aa55f96): fill_kobj_path: path =
> '/devices/virtual/bdi/0:34'
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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