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: 1 PID: 11033 Comm: syz-executor2 Not tainted 4.4.153-g5e24b4e #90
device lo entered promiscuous mode
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b6f2e000 task.stack: ffff8800ba6d0000
RIP: 0010:[<ffffffff81421415>]  [<ffffffff81421415>] unlock_page+0x115/0x150 mm/filemap.c:817
RSP: 0018:ffff8800ba6d78a0  EFLAGS: 00010212
RAX: ffffffff83a6f940 RBX: ffffea0002db0000 RCX: ffffc90001872000
RDX: 00000000000206ed RSI: ffffffff815195a9 RDI: ffff8800b6f2e8dc
RBP: ffff8800ba6d78c0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffea0002db0300 R14: ffffea0002db0008 R15: ffff8800ba6d7988
FS:  00007f6cc9682700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f951b81f000 CR3: 00000001d19d5000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea0002db0000 dffffc0000000000 ffffea0002db0300 ffffea0002db0008
 ffff8800ba6d79b0 ffffffff812cf25d ffff8800ba6d7958 ffff8800ba6d7af8
 ffff8801d3400500 1ffff100174daf25 0000000100000000 ffff8800ba6d7ae8
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
 [<ffffffff812d5200>] SYSC_futex kernel/futex.c:3286 [inline]
 [<ffffffff812d5200>] SyS_futex+0x1f0/0x300 kernel/futex.c:3254
 [<ffffffff838cc865>] entry_SYSCALL_64_fastpath+0x22/0x9e
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 <ffff8800ba6d78a0>
---[ end trace c36c172ebab2ab67 ]---