syzbot

INFO: task syz-executor235:3915 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor235 D29088  3915   3911 0x00000004
 ffff8801d7c8b000 0000000000000000 ffff8801bc071f80 ffff8801d9a6b000
 ffff8801db321c18 ffff8801d6e0fac8 ffffffff839e909d ffffffff81235647
 0000000000000000 ffff8801d7c8b8c0 0000000600000007 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839f5cd8>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839f5cd8>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee7587>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff8122c270>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff8122c270>] down_write_nested+0x60/0xa0 kernel/locking/rwsem.c:174
 [<ffffffff815aa01a>] inode_lock_nested include/linux/fs.h:801 [inline]
 [<ffffffff815aa01a>] filename_create+0x17a/0x490 fs/namei.c:3639
 [<ffffffff815ac49b>] user_path_create fs/namei.c:3697 [inline]
 [<ffffffff815ac49b>] SYSC_mkdirat fs/namei.c:3841 [inline]
 [<ffffffff815ac49b>] SyS_mkdirat+0xbb/0x260 fs/namei.c:3833
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/520:
 #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/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] 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
2 locks held by syz-executor235/3915:
 #0:  (sb_writers#8){.+.+.+}, at: [<ffffffff815e0a8f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#8){.+.+.+}, at: [<ffffffff815e0a8f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&type->i_mutex_dir_key#3/1){+.+.+.}, at: [<ffffffff815aa01a>] inode_lock_nested include/linux/fs.h:801 [inline]
 #1:  (&type->i_mutex_dir_key#3/1){+.+.+.}, at: [<ffffffff815aa01a>] filename_create+0x17a/0x490 fs/namei.c:3639

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

NMI backtrace for cpu 0
CPU: 0 PID: 520 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8437d08 ffffffff81eb32a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d8437d40
 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
 [<ffffffff839fa15c>] 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: 3914 Comm: syz-executor235 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8539800 task.stack: ffff8801d7128000
RIP: 0010:[<ffffffff8123562a>] 
c [<ffffffff8123562a>] mark_held_locks+0xaa/0x130 kernel/locking/lockdep.c:2652
RSP: 0018:ffff8801d712f7b0  EFLAGS: 00000093
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 1ffff1003b0a741d
RDX: 0000000000000002 RSI: ffff8801d853a0f0 RDI: ffff8801d853a112
RBP: ffff8801d712f7f0 R08: ffff8801d853a0e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d853a0c8
R13: ffffed003b0a7418 R14: ffff8801d8539800 R15: dffffc0000000000
FS:  00007fe2f5e78700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa2cf355000 CR3: 00000001b94e6000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000000
c ffff8801d853a0c0
c 0000000600000007
c ffff8801d8539800
c
 ffffffff839f969a
c ffff8801d712f948
c ffff8801ba8b6318
c 0000000000000001
c
 ffff8801d712f810
c ffffffff81235a3b
c 0000000000000296
c ffff8801ba8b6318
c
Call Trace:
 [<ffffffff81235a3b>] __trace_hardirqs_on_caller kernel/locking/lockdep.c:2689 [inline]
 [<ffffffff81235a3b>] trace_hardirqs_on_caller+0x38b/0x590 kernel/locking/lockdep.c:2736
 [<ffffffff81235c4d>] trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
 [<ffffffff839f969a>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 [<ffffffff839f969a>] _raw_spin_unlock_irqrestore+0x5a/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81221729>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff81221729>] prepare_to_wait_event+0x1d9/0x450 kernel/sched/wait.c:238
 [<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
 [<ffffffff8191adc3>] fuse_lookup_name+0x253/0x5d0 fs/fuse/dir.c:369
 [<ffffffff8191b22d>] fuse_lookup+0xed/0x3a0 fs/fuse/dir.c:406
 [<ffffffff81593e4c>] lookup_real fs/namei.c:1522 [inline]
 [<ffffffff81593e4c>] __lookup_hash+0x11c/0x190 fs/namei.c:1542
 [<ffffffff815aa046>] filename_create+0x1a6/0x490 fs/namei.c:3640
 [<ffffffff815ac49b>] user_path_create fs/namei.c:3697 [inline]
 [<ffffffff815ac49b>] SYSC_mkdirat fs/namei.c:3841 [inline]
 [<ffffffff815ac49b>] SyS_mkdirat+0xbb/0x260 fs/namei.c:3833
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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