page:ffffea0002db0000 count:2 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000004004(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: 0 PID: 8464 Comm: syz-executor7 Not tainted 4.4.153-g5e24b4e #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800a4dbb000 task.stack: ffff8800b9240000
RIP: 0010:[<ffffffff81421415>]  [<ffffffff81421415>] unlock_page+0x115/0x150 mm/filemap.c:817
RSP: 0018:ffff8800b9247828  EFLAGS: 00010212
RAX: ffffffff83a6f940 RBX: ffffea0002db0000 RCX: ffffc900070f2000
RDX: 00000000000237f2 RSI: ffffffff815195a9 RDI: ffff8800a4dbb8dc
RBP: ffff8800b9247848 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffea0002db0300 R14: ffffea0002db0008 R15: ffff8800b9247910
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f577bb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f5782c30 CR3: 00000001d7d91000 CR4: 00000000001606f0
Stack:
 ffffea0002db0000 dffffc0000000000 ffffea0002db0300 ffffea0002db0008
 ffff8800b9247938 ffffffff812cf25d 0000000000000000 ffff8800b9247a80
 ffff8800b6ac4f00 1ffff10017248f16 00000001b0efceb0 ffff8800b9247a70
Call Trace:
 [<ffffffff812cf25d>] get_futex_key+0x8ad/0xdc0 kernel/futex.c:598
 [<ffffffff812d0f17>] futex_requeue+0x1e7/0x1690 kernel/futex.c:1780
 [<ffffffff812d3a24>] do_futex+0x204/0x17f0 kernel/futex.c:3248
 [<ffffffff812d5b19>] C_SYSC_futex kernel/futex_compat.c:200 [inline]
 [<ffffffff812d5b19>] 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
 [<ffffffff838ce1c3>] sysenter_flags_fixed+0xd/0x1a
Code: e8 48 8d 04 c0 49 8d 3c c6 e8 88 bd df ff 5b 41 5c 41 5d 41 5e 5d c3 e8 8a 31 f3 ff 48 c7 c6 e0 bb a9 83 48 89 df e8 bb ee 06 00 <0f> 0b 48 89 df e8 51 d3 0d 00 e9 0a ff ff ff e8 47 d3 0d 00 e9 
RIP  [<ffffffff81421415>] unlock_page+0x115/0x150 mm/filemap.c:817
 RSP <ffff8800b9247828>
---[ end trace 0291d345ba426fec ]---