page:ffffea0007198000 count:2 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000004004(referenced|head)
page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
------------[ cut here ]------------
kernel BUG at mm/filemap.c:817!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 6279 Comm: syz-executor0 Not tainted 4.4.148-gf057ff9 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d260e000 task.stack: ffff8801d2bb8000
RIP: 0010:[<ffffffff81420dd5>]  [<ffffffff81420dd5>] unlock_page+0x115/0x150 mm/filemap.c:817
RSP: 0018:ffff8801d2bbf828  EFLAGS: 00010216
RAX: ffffffff83a6f940 RBX: ffffea0007198000 RCX: ffffc90000e25000
RDX: 000000000001f685 RSI: ffffffff81517889 RDI: ffff8801d260e8dc
RBP: ffff8801d2bbf848 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffea0007198300 R14: ffffea0007198008 R15: ffff8801d2bbf910
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f57a2b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000020400000 CR3: 00000000b463d000 CR4: 00000000001606f0
Stack:
 ffffea0007198000 dffffc0000000000 ffffea0007198300 ffffea0007198008
 ffff8801d2bbf938 ffffffff812cec0d ffff8801d9bcb280 ffff8801d2bbfa80
 ffff8800b59d1e00 1ffff1003a577f16 0000000100000000 ffff8801d2bbfa70
Call Trace:
 [<ffffffff812cec0d>] get_futex_key+0x8ad/0xdc0 kernel/futex.c:598
 [<ffffffff812d08c7>] futex_requeue+0x1e7/0x1690 kernel/futex.c:1780
 [<ffffffff812d33d4>] do_futex+0x204/0x17f0 kernel/futex.c:3248
 [<ffffffff812d54c9>] C_SYSC_futex kernel/futex_compat.c:200 [inline]
 [<ffffffff812d54c9>] compat_SyS_futex+0x1d9/0x2f0 kernel/futex_compat.c:174
 [<ffffffff81006d94>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d94>] do_fast_syscall_32+0x324/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838cc003>] sysenter_flags_fixed+0xd/0x1a
Code: e8 48 8d 04 c0 49 8d 3c c6 e8 b8 bc df ff 5b 41 5c 41 5d 41 5e 5d c3 e8 7a 31 f3 ff 48 c7 c6 e0 bb a9 83 48 89 df e8 bb ee 06 00 <0f> 0b 48 89 df e8 31 c5 0d 00 e9 0a ff ff ff e8 27 c5 0d 00 e9 
RIP  [<ffffffff81420dd5>] unlock_page+0x115/0x150 mm/filemap.c:817
 RSP <ffff8801d2bbf828>
---[ end trace b490cb74b60a699f ]---