Date:   Sat, 09 Dec 2017 02:43:00 -0800
From:   syzbot 
        <bot+48594378e9851eab70bcd6f99327c7db58c5a28a@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, syzkaller-bugs@...glegroups.com
Subject: INFO: task hung in __blkdev_get

Hello,

syzkaller hit the following crash on  
4131d5166185d0d75b5f1d4bf362a9e0bac05598
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


INFO: task blkid:3090 blocked for more than 120 seconds.
       Not tainted 4.15.0-rc1-mm1+ #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid           D23696  3090   3062 0x00000004
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_get+0x158/0x10e0 fs/block_dev.c:1439
  blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591
  blkdev_open+0x1e4/0x270 fs/block_dev.c:1749
  do_dentry_open+0x682/0xd70 fs/open.c:752
  vfs_open+0x107/0x230 fs/open.c:866
  do_last fs/namei.c:3379 [inline]
  path_openat+0x1157/0x3530 fs/namei.c:3519
  do_filp_open+0x25b/0x3b0 fs/namei.c:3554
  do_sys_open+0x502/0x6d0 fs/open.c:1059
  SYSC_open fs/open.c:1077 [inline]
  SyS_open+0x2d/0x40 fs/open.c:1072
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x7fe5c5bfc120
RSP: 002b:00007ffde0d34f08 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe5c5bfc120
RDX: 00007ffde0d35f34 RSI: 0000000000000000 RDI: 00007ffde0d35f34
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000211e030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Showing all locks held in the system:
2 locks held by khungtaskd/675:
  #0:  (rcu_read_lock){....}, at: [<000000007fb79bbe>]  
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
  #0:  (rcu_read_lock){....}, at: [<000000007fb79bbe>] watchdog+0x1c5/0xd60  
kernel/hung_task.c:249
  #1:  (tasklist_lock){.+.+}, at: [<0000000035358c26>]  
debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
1 lock held by rsyslogd/2973:
  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000001261d81>]  
__fdget_pos+0x131/0x1a0 fs/file.c:770
2 locks held by getty/3055:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3056:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3057:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3058:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3059:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3060:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
2 locks held by getty/3061:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005cc11435>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000008d2b0f7>]  
n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
1 lock held by syzkaller346228/3087:
  #0:  (&bdev->bd_mutex){+.+.}, at: [<0000000099fa8891>]  
__blkdev_put+0xa7/0x7c0 fs/block_dev.c:1757
1 lock held by blkid/3090:
  #0:  (&bdev->bd_mutex){+.+.}, at: [<00000000d4caea9e>]  
__blkdev_get+0x158/0x10e0 fs/block_dev.c:1439

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

NMI backtrace for cpu 0
CPU: 0 PID: 675 Comm: khungtaskd Not tainted 4.15.0-rc1-mm1+ #29
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:517
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc1-mm1+ #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
task: 0000000064c7084b task.stack: 00000000bb7e08d1
RIP: 0010:sched_ttwu_pending+0x0/0x270 kernel/sched/core.c:1584
RSP: 0018:ffff8801db507d68 EFLAGS: 00000046
RAX: 0000000000000003 RBX: 0000000000027900 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801da3894a0
RBP: ffff8801db507e90 R08: 0000000000000001 R09: ffff88021fff8048
R10: ffff88021fff8050 R11: ffff88021fff805d R12: ffff8801da388300
R13: 1ffff1003b6a0fb1 R14: ffff8801db507e68 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe5c5bfc110 CR3: 00000001d1b96000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  <IRQ>
  smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277
  reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:931
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffff8801da397da8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02
RAX: dffffc0000000000 RBX: 1ffff1003b472fb8 RCX: 0000000000000000
RDX: 1ffffffff0bd9744 RSI: 0000000000000001 RDI: ffffffff85ecba20
RBP: ffff8801da397da8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffff8801da397e60 R14: ffffffff865eca20 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
  start_secondary+0x2dd/0x3e0 arch/x86/kernel/smpboot.c:277
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237
Code: ff ff 4c 89 85 70 ff ff ff e8 ad 12 5a 00 48 8b 95 68 ff ff ff 4c 8b  
85 70 ff ff ff e9 19 fe ff ff 66 2e 0f 1f 84 00 00 00 00 00 <55> 48 89 e5  
41 57 41 56 41 55 4c 8d ad 78 ff ff ff 49 be 00 00


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

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