syzbot

random: crng init done
INFO: task blkid:3373 blocked for more than 120 seconds.
      Not tainted 4.9.66-gb763480 #103
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid           D28208  3373   1866 0x00000004
 ffff8801cefb8000 0000000000000000 ffff8801cd990540 ffff8801da29b000
 ffff8801db321418 ffff8801ca087708 ffffffff838981cb 0000000000000000
 0000000000000007 00ff8801cefb8000 ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389976f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff8389a0f3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583
 [<ffffffff8389f702>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8389f702>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff8162a23c>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
 [<ffffffff8162c10b>] blkdev_get+0x33b/0x960 fs/block_dev.c:1416
 [<ffffffff8162c935>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1571
 [<ffffffff81563227>] do_dentry_open+0x607/0xc60 fs/open.c:766
 [<ffffffff81566cd5>] vfs_open+0x105/0x220 fs/open.c:879
 [<ffffffff8159d44c>] do_last fs/namei.c:3408 [inline]
 [<ffffffff8159d44c>] path_openat+0x5ac/0x2910 fs/namei.c:3531
 [<ffffffff815a2fa7>] do_filp_open+0x197/0x290 fs/namei.c:3566
 [<ffffffff815677b2>] do_sys_open+0x352/0x4c0 fs/open.c:1072
 [<ffffffff8156794d>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156794d>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe05>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe05>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355d0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3150:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815cf91f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3238:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a7b92>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82001d84>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syzkaller946102/3370:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81629a0c>] __blkdev_put+0xbc/0x7e0 fs/block_dev.c:1579
1 lock held by blkid/3373:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a23c>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.66-gb763480 #103
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d99dfd00 ffffffff81d90749 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba170 ffff8801d99dfd38
 ffffffff81d9b86d 0000000000000000 0000000000000000 ffff8801cefb8418
Call Trace:
 [<ffffffff81d90749>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90749>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b86d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9b9a7>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba264>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813703d0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703d0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703d0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703d0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a9c2a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:437
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838a8606