INFO: task syz-executor0:25880 blocked for more than 140 seconds.
      Not tainted 4.9.123-g8dd3fc2 #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D29608 25880   9939 0x00000004
 ffff8801cf890000 ffff8801ba09c000 ffff8801aaa50540 ffff8801d8491800
 ffff8801db321c18 ffff8801d55bf8e0 ffffffff839f0dbd ffffffff81237907
 0000000000000000 ffff8801cf8908c0 0000000600000007 ffff8801db3224e8
Call Trace:
 [<ffffffff839f23bf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fc7e4>] rwsem_down_read_failed+0x1e4/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81eed978>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff839fb712>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff839fb712>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff815a9f2c>] inode_lock_shared include/linux/fs.h:776 [inline]
 [<ffffffff815a9f2c>] do_last fs/namei.c:3314 [inline]
 [<ffffffff815a9f2c>] path_openat+0x17dc/0x3590 fs/namei.c:3534
 [<ffffffff815affa7>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff81572345>] file_open_name+0x1f5/0x2b0 fs/open.c:999
 [<ffffffff812f5e0c>] acct_on kernel/acct.c:204 [inline]
 [<ffffffff812f5e0c>] SYSC_acct kernel/acct.c:283 [inline]
 [<ffffffff812f5e0c>] SyS_acct+0xec/0x840 kernel/acct.c:270
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] 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: [<ffffffff81368a9c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81368a9c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81428308>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3664:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815dc88c>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff815774fe>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff815774fe>] vfs_write+0x3ae/0x530 fs/read_write.c:556
1 lock held by rsyslogd/3666:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815dc88c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3762:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffe62>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821253c2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
3 locks held by syz-executor0/25880:
 #0:  (acct_on_mutex){+.+.+.}, at: [<ffffffff812f5da3>] SYSC_acct kernel/acct.c:282 [inline]
 #0:  (acct_on_mutex){+.+.+.}, at: [<ffffffff812f5da3>] SyS_acct+0x83/0x840 kernel/acct.c:270
 #1:  (sb_writers#12){.+.+.+}, at: [<ffffffff815e516f>] sb_start_write include/linux/fs.h:1573 [inline]
 #1:  (sb_writers#12){.+.+.+}, at: [<ffffffff815e516f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #2:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9f2c>] inode_lock_shared include/linux/fs.h:776 [inline]
 #2:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9f2c>] do_last fs/namei.c:3314 [inline]
 #2:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9f2c>] path_openat+0x17dc/0x3590 fs/namei.c:3534
2 locks held by syz-executor0/25883:
 #0:  (sb_writers#12){.+.+.+}, at: [<ffffffff815e516f>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#12){.+.+.+}, at: [<ffffffff815e516f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9625>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9625>] do_last fs/namei.c:3312 [inline]
 #1:  (&sb->s_type->i_mutex_key#19){++++++}, at: [<ffffffff815a9625>] path_openat+0xed5/0x3590 fs/namei.c:3534

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.123-g8dd3fc2 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84d7d08 ffffffff81eb9689 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d84d7d40
 ffffffff81ec49c7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec49c7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec495a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81369034>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81369034>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81369034>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81369034>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01e5c>] 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: 25870 Comm: syz-executor0 Not tainted 4.9.123-g8dd3fc2 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88019cef8000 task.stack: ffff8801cd990000
RIP: 0010:[<ffffffff8127e5c7>] 
c [<ffffffff8127e5c7>] __rcu_read_unlock+0x87/0x1a0 kernel/rcu/update.c:233
RSP: 0018:ffff8801cd997808  EFLAGS: 00000217
RAX: 0000000000000000 RBX: ffff88019cef8000 RCX: ffffc90001e89000
RDX: 0000000000000000 RSI: ffffffff8143b280 RDI: ffff88019cef83e4
RBP: ffff8801cd997818 R08: ffff88019cef8910 R09: 0000000000000001
R10: ffff88019cef8000 R11: 1ffff100339df11d R12: ffff88019cef83e0
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8801d9c16548
FS:  00007f494c8ac700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001459000 CR3: 00000001bafd7000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801d9c16548
c 0000000000000000
c ffff8801cd997880
c ffffffff8143b285
c
 ffffffff8143b160
c ffffed00339df118
c ffff88019cef88c8
c 0000000000000041
c
 ffff8801d9c16550
c 0000000000000000
c ffff8801d9c16548
c 0000000000000001
c
Call Trace:
 [<ffffffff8143b285>] rcu_read_unlock include/linux/rcupdate.h:930 [inline]
 [<ffffffff8143b285>] find_get_entry+0x125/0x540 mm/filemap.c:1130
 [<ffffffff8143c5db>] pagecache_get_page+0x4b/0x720 mm/filemap.c:1201
 [<ffffffff816287d2>] find_get_page_flags include/linux/pagemap.h:264 [inline]
 [<ffffffff816287d2>] __find_get_block_slow+0xc2/0x330 fs/buffer.c:212
 [<ffffffff81628d7e>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81629b89>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81629b89>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff8162d52d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818c987b>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818c987b>] fat12_ent_bread+0x13b/0x400 fs/fat/fatent.c:75
 [<ffffffff818cca4c>] fat_ent_read_block fs/fat/fatent.c:441 [inline]
 [<ffffffff818cca4c>] fat_count_free_clusters+0x44c/0xa50 fs/fat/fatent.c:676
 [<ffffffff818d2f24>] fat_statfs+0x394/0x4a0 fs/fat/inode.c:815
 [<ffffffff816225f3>] statfs_by_dentry+0x133/0x200 fs/statfs.c:60
 [<ffffffff81622703>] vfs_statfs+0x43/0x220 fs/statfs.c:70
 [<ffffffff8162298b>] user_statfs+0xab/0x120 fs/statfs.c:85
 [<ffffffff81622a7f>] SYSC_statfs+0x7f/0xf0 fs/statfs.c:175
 [<ffffffff81622e9d>] SyS_statfs+0x1d/0x30 fs/statfs.c:172
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c