page:ffffea0002dc8000 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: 7904 Comm: syz-executor1 Not tainted 4.4.150-g5541782 #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cb166000 task.stack: ffff8801bc3f0000
RIP: 0010:[<ffffffff81421375>]  [<ffffffff81421375>] unlock_page+0x115/0x150 mm/filemap.c:817
RSP: 0018:ffff8801bc3f77c8  EFLAGS: 00010206
RAX: ffffffff83a6f940 RBX: ffffea0002dc8000 RCX: ffffc9000243c000
RDX: 000000000001bdd0 RSI: ffffffff815184c9 RDI: ffff8801cb1668dc
RBP: ffff8801bc3f77e8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffea0002dc8300 R14: ffffea0002dc8008 R15: ffff8801bc3f78b0
FS:  00007f1272325700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000210009bf CR3: 00000000afad2000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea0002dc8000 dffffc0000000000 ffffea0002dc8300 ffffea0002dc8008
 ffff8801bc3f78d8 ffffffff812cf1ad 0000000000000000 ffff8801bc3f7ab0
 ffff8800baba8000 1ffff1003787ef0a 0000000100000000 ffff8801bc3f7aa0
Call Trace:
 [<ffffffff812cf1ad>] get_futex_key+0x8ad/0xdc0 kernel/futex.c:598
 [<ffffffff812cfbf9>] futex_wait_setup+0xd9/0x330 kernel/futex.c:2376
 [<ffffffff812d00ff>] futex_wait+0x2af/0x600 kernel/futex.c:2439
 [<ffffffff812d3a14>] do_futex+0x2a4/0x17f0 kernel/futex.c:3226
 [<ffffffff812d5150>] SYSC_futex kernel/futex.c:3286 [inline]
 [<ffffffff812d5150>] SyS_futex+0x1f0/0x300 kernel/futex.c:3254
 [<ffffffff838cb0a5>] entry_SYSCALL_64_fastpath+0x22/0x9e
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 11 c9 0d 00 e9 0a ff ff ff e8 07 c9 0d 00 e9 
RIP  [<ffffffff81421375>] unlock_page+0x115/0x150 mm/filemap.c:817
 RSP <ffff8801bc3f77c8>
---[ end trace b0981655f40bdf7b ]---