syzbot

IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
INFO: task syz-executor0:4386 blocked for more than 140 seconds.
      Not tainted 4.9.113-g9905591 #14
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D29144  4386   3910 0x00000004
 ffff8801cf481800 0000000000000000 ffff8801ce2e8000 ffffffff84629800
 ffff8801db221c18 ffff8801ba13f680 ffffffff839e929d ffffffff81235647
 0000000000000000 ffff8801cf4820c0 0000000600000007 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea89f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839f4cc4>] rwsem_down_read_failed+0x1e4/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81ee7558>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff839f3bf2>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff839f3bf2>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff81594cb1>] inode_lock_shared include/linux/fs.h:776 [inline]
 [<ffffffff81594cb1>] lookup_slow+0x141/0x470 fs/namei.c:1645
 [<ffffffff815a1336>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a3c96>] lookup_last fs/namei.c:2266 [inline]
 [<ffffffff815a3c96>] path_lookupat.isra.41+0x186/0x410 fs/namei.c:2283
 [<ffffffff815a9747>] filename_lookup.part.55+0x177/0x370 fs/namei.c:2317
 [<ffffffff815a9b03>] filename_lookup fs/namei.c:2310 [inline]
 [<ffffffff815a9b03>] user_path_at_empty+0x53/0x70 fs/namei.c:2578
 [<ffffffff81580ae6>] user_path_at include/linux/namei.h:55 [inline]
 [<ffffffff81580ae6>] vfs_fstatat+0xc6/0x170 fs/stat.c:106
 [<ffffffff81581d89>] vfs_lstat fs/stat.c:129 [inline]
 [<ffffffff81581d89>] SYSC_newlstat+0x89/0x100 fs/stat.c:283
 [<ffffffff815820cd>] SyS_newlstat+0x1d/0x30 fs/stat.c:277
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fa193>] 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: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3761:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8342>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/4386:
 #0:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81594cb1>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81594cb1>] lookup_slow+0x141/0x470 fs/namei.c:1645
1 lock held by syz-executor0/4388:
 #0:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81594cb1>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81594cb1>] lookup_slow+0x141/0x470 fs/namei.c:1645
2 locks held by syz-executor0/4389:
 #0:  (sb_writers#10){.+.+.+}, at: [<ffffffff815e0a8f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#10){.+.+.+}, at: [<ffffffff815e0a8f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81568e21>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&type->i_mutex_dir_key#4){++++++}, at: [<ffffffff81568e21>] chmod_common+0x171/0x450 fs/open.c:543

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g9905591 #14
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8587d08 ffffffff81eb32a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d8587d40
 ffffffff81ebe5a7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] 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
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa35c>] 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: 4385 Comm: syz-executor0 Not tainted 4.9.113-g9905591 #14
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cf97b000 task.stack: ffff8801ba130000
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] constant_test_bit arch/x86/include/asm/bitops.h:311 [inline]
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] test_ti_thread_flag include/linux/thread_info.h:63 [inline]
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] test_tsk_thread_flag include/linux/sched.h:3439 [inline]
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] signal_pending include/linux/sched.h:3465 [inline]
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] signal_pending_state include/linux/sched.h:3482 [inline]
RIP: 0010:[<ffffffff812215e9>] 
c [<ffffffff812215e9>] prepare_to_wait_event+0x99/0x450 kernel/sched/wait.c:214
RSP: 0018:ffff8801ba1377b8  EFLAGS: 00000046
RAX: 0000000000000001 RBX: 1ffff10037426efa RCX: dffffc0000000000
RDX: ffff8801cf97b000 RSI: 1ffff10039f2f600 RDI: ffff8801cec6a564
RBP: ffff8801ba137858 R08: 0000000000000286 R09: 0000000000000001
R10: ffff8801cf97b000 R11: 1ffff10039f2f722 R12: ffff8801ba137830
R13: ffff8801ba1378b0 R14: ffff8801cec6a560 R15: 0000000000000001
FS:  00007f7956f7e700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc5e01d9280 CR3: 00000001ceee2000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801ba1377e0
c 0000000000000246
c ffff8801cf97b000
c 0000000041b58ab3
c
 ffffffff843bbae3
c ffffffff81221550
c 0000000000000246
c ffff8801cf97b000
c
 ffffffff83db4480
c 00000000000001cc
c 0000000000000000
c ffff8801cec6a4c0
c
Call Trace:
 [<ffffffff81907bbe>] request_wait_answer+0x22e/0x6e0 fs/fuse/dev.c:459
 [<ffffffff819086c9>] __fuse_request_send+0x109/0x1b0 fs/fuse/dev.c:480
 [<ffffffff819087cd>] fuse_request_send+0x5d/0x70 fs/fuse/dev.c:493
 [<ffffffff81912a24>] fuse_simple_request+0x2f4/0x660 fs/fuse/dev.c:551
 [<ffffffff8191cffb>] fuse_do_setattr+0x68b/0x11e0 fs/fuse/dir.c:1722
 [<ffffffff8191dd42>] fuse_setattr+0x1f2/0x510 fs/fuse/dir.c:1822
 [<ffffffff815d3f90>] notify_change2+0xac0/0xdf0 fs/attr.c:313
 [<ffffffff81568ec7>] chmod_common+0x217/0x450 fs/open.c:549
 [<ffffffff8156ccfd>] SYSC_fchmodat fs/open.c:582 [inline]
 [<ffffffff8156ccfd>] SyS_fchmodat fs/open.c:574 [inline]
 [<ffffffff8156ccfd>] SYSC_chmod fs/open.c:594 [inline]
 [<ffffffff8156ccfd>] SyS_chmod+0xad/0x130 fs/open.c:592
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fa193>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c