IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
INFO: task syz-executor0:3878 blocked for more than 120 seconds.
      Not tainted 4.9.101-gaef17a5 #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D27672  3878      1 0x00000004
 ffff880197690000 ffff8801d7ccc540 ffff8801d94e5a40 ffff88018d408000
 ffff8801db221b98 ffff88019769fb40 ffffffff839e39bd 0000000000000002
 0000000041b58ab3 ffffffff843b8b43 00ffffff8121f220 ffff8801db222468
Call Trace:
 [<ffffffff839e4fbf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81600249>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff816004b7>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff81600607>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81600607>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff816181c3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff816181c3>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff81576e75>] generic_shutdown_super+0x75/0x300 fs/super.c:423
 [<ffffffff815777af>] kill_block_super+0x9f/0x120 fs/super.c:1127
 [<ffffffff81577b25>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff81578531>] deactivate_super+0x91/0xd0 fs/super.c:341
 [<ffffffff815da652>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815da786>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119607c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f4893>] 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: [<ffffffff8136477c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136477c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423c90>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3771:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f2a62>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cd32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3878:
 #0:  (&type->s_umount_key#37){+.+...}, at: [<ffffffff81578529>] deactivate_super+0x89/0xd0 fs/super.c:340

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.101-gaef17a5 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d86bfd08 ffffffff81eb1009 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7da0 ffff8801d86bfd40
 ffffffff81ebc307 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb1009>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb1009>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc307>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc29a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7ea4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364d14>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364d14>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364d14>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364d14>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad9d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f4a5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5217 Comm: kworker/u4:7 Not tainted 4.9.101-gaef17a5 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:0)
c
task: ffff8801b98e4800 task.stack: ffff8801d9238000
RIP: 0010:[<ffffffff812325ba>] 
c [<ffffffff812325ba>] mark_lock+0xaa/0x1280 kernel/locking/lockdep.c:3039
RSP: 0018:ffff8801d923f520  EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffff8801b98e50f0 RCX: 1ffff1003731ca22
RDX: 1ffffffff0abda06 RSI: ffff8801b98e50f0 RDI: ffffffff855ed030
RBP: ffff8801d923f568 R08: ffff8801b98e5110 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff855ed000
R13: 0000000000000004 R14: 0000000000000002 R15: ffff8801b98e4800
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b5d9e6d7a8 CR3: 000000000461e000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801b98e4800
c ffffffff846deea0
c 00000000000001c4
c ffff8801d9c12bc8
c
 0000000000000001
c ffff8801b98e50c8
c ffffed003731ca18
c ffff8801b98e4800
c
 dffffc0000000000
c ffff8801d923f5b8
c ffffffff81233857
c ffff8801b98e4800
c
Call Trace:
 [<ffffffff81233857>] mark_held_locks+0xc7/0x130 kernel/locking/lockdep.c:2660
 [<ffffffff81233b26>] __trace_hardirqs_on_caller kernel/locking/lockdep.c:2681 [inline]
 [<ffffffff81233b26>] trace_hardirqs_on_caller+0x266/0x590 kernel/locking/lockdep.c:2736
 [<ffffffff81233e5d>] trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
 [<ffffffff81621a93>] lookup_bh_lru fs/buffer.c:1344 [inline]
 [<ffffffff81621a93>] __find_get_block+0x183/0x4c0 fs/buffer.c:1356
 [<ffffffff81622959>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81622959>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff816262fd>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818c8dab>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818c8dab>] __fat_write_inode+0x2ab/0x980 fs/fat/inode.c:844
 [<ffffffff818ccfb9>] fat_write_inode+0x79/0x170 fs/fat/inode.c:893
 [<ffffffff815ff94d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff815ff94d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff81600c4c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff81601c4f>] wb_writeback+0x2cf/0xbd0 fs/fs-writeback.c:1760
 [<ffffffff8160b17e>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff8160b17e>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118ae71>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bc66>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad9d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f4a5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
c01 
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c<0f> 
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cbd 
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c