b_state=0x00000029, b_size=512
device loop5 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop5 blocksize: 4096
INFO: task syz-executor5:16958 blocked for more than 140 seconds.
      Not tainted 4.9.116-g52be322 #17
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D28360 16958   3897 0x00000004
 ffff8801c9cde000 ffff8801d40a6f40 ffff8801d40a6f40 ffff880197efc800
 ffff8801db221c18 ffff88019bebf4a8 ffffffff839ead0d dffffc0000000000
 ffff8801cbc71190 ffff88019bebf468 00ff8801c9cde8c0 ffff8801db2224e8
Call Trace:
 [<ffffffff839ec30f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff815c7ec2>] d_wait_lookup fs/dcache.c:2455 [inline]
 [<ffffffff815c7ec2>] d_alloc_parallel+0xeb2/0x17c0 fs/dcache.c:2537
 [<ffffffff81594e7c>] lookup_slow+0x19c/0x470 fs/namei.c:1650
 [<ffffffff815a14a6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a31c9>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a423d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815ab8e7>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e0bd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e3e0>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff8156e3e0>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fbc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136677c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136677c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425e07>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3686:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d835c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3782:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f9db2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82120212>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor5/16958:
 #0:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff81594e21>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff81594e21>] lookup_slow+0x141/0x470 fs/namei.c:1645

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.116-g52be322 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d96d7d08 ffffffff81eb46a9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d96d7d40
 ffffffff81ebf9a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb46a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb46a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf9a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf93a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d14>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d14>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d14>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d14>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fbddc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 16960 Comm: syz-executor3 Not tainted 4.9.116-g52be322 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801a676c800 task.stack: ffff88019ffe8000
RIP: 0010:[<ffffffff82150f5b>] 
c [<ffffffff82150f5b>] inb arch/x86/include/asm/io.h:316 [inline]
RIP: 0010:[<ffffffff82150f5b>] 
c [<ffffffff82150f5b>] io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:414
RSP: 0018:ffff88019ffef698  EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: ffffffff82150f01 RDI: ffffffff864aaeb8
RBP: ffff88019ffef6a8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff864aae80
R13: 0000000000000020 R14: fffffbfff0c95617 R15: fffffbfff0c955d9
FS:  00007fa40d34b700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7318324ec0 CR3: 00000001c820d000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff864aae80
c 000000000000270b
c ffff88019ffef6f8
c ffffffff82152b24
c
 ffffffff81edf998
c ffffffff864aaec8
c ffffffff864ab0ba
c ffffffff864aae80
c
 0000000000000074
c ffffffff82152c70
c dffffc0000000000
c 0000000000000074
c
Call Trace:
 [<ffffffff82152b24>] serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 [<ffffffff82152b24>] wait_for_xmitr+0x94/0x1e0 drivers/tty/serial/8250/8250_port.c:1998
 [<ffffffff82152c8f>] serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3104
 [<ffffffff8213b4b9>] uart_console_write+0x59/0xf0 drivers/tty/serial/serial_core.c:1859
 [<ffffffff8215eea8>] serial8250_console_write+0x528/0x820 drivers/tty/serial/8250/8250_port.c:3170
 [<ffffffff8214ba0f>] univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:594
 [<ffffffff8125bccd>] call_console_drivers.isra.18.constprop.28+0x1ad/0x360 kernel/printk/printk.c:1589
 [<ffffffff8125eacf>] console_unlock+0x42f/0xb40 kernel/printk/printk.c:2449
 [<ffffffff8125f628>] vprintk_emit+0x448/0x790 kernel/printk/printk.c:1903
 [<ffffffff8125f998>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
 [<ffffffff8125f9bd>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
 [<ffffffff8142cbdc>] vprintk_func kernel/printk/internal.h:36 [inline]
 [<ffffffff8142cbdc>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
 [<ffffffff816d6b32>] proc_parse_options+0x302/0x310 fs/proc/root.c:68
 [<ffffffff816d6b8c>] proc_remount+0x4c/0x70 fs/proc/root.c:82
 [<ffffffff8157d731>] do_remount_sb2+0x351/0x7d0 fs/super.c:825
 [<ffffffff815e6133>] do_remount fs/namespace.c:2328 [inline]
 [<ffffffff815e6133>] do_mount+0xf93/0x2740 fs/namespace.c:2826
 [<ffffffff815e82be>] SYSC_mount fs/namespace.c:3051 [inline]
 [<ffffffff815e82be>] SyS_mount+0xfe/0x110 fs/namespace.c:3028
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fbc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
c24 
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c