page:ffffea0002bf0000 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: 25580 Comm: syz-executor4 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801bc82b000 task.stack: ffff8801bb828000
RIP: 0010:[<ffffffff814213c5>]  [<ffffffff814213c5>] unlock_page+0x115/0x150 mm/filemap.c:817
RSP: 0018:ffff8801bb82f7c8  EFLAGS: 00010216
RAX: ffffffff83a6f940 RBX: ffffea0002bf0000 RCX: ffffc90006ec1000
RDX: 00000000000215ec RSI: ffffffff81519559 RDI: ffff8801bc82b8dc
RBP: ffff8801bb82f7e8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffea0002bf0300 R14: ffffea0002bf0008 R15: ffff8801bb82f8b0
FS:  00007faef041b700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020622c40 CR3: 00000000b7ac8000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea0002bf0000 dffffc0000000000 ffffea0002bf0300 ffffea0002bf0008
 ffff8801bb82f8d8 ffffffff812cf20d 0000000000000000 ffff8801bb82fab0
 ffff8801d4b3b700 1ffff10037705f0a 0000000100000000 ffff8801bb82faa0
Call Trace:
 [<ffffffff812cf20d>] get_futex_key+0x8ad/0xdc0 kernel/futex.c:598
 [<ffffffff812cfc59>] futex_wait_setup+0xd9/0x330 kernel/futex.c:2376
 [<ffffffff812d015f>] futex_wait+0x2af/0x600 kernel/futex.c:2439
 [<ffffffff812d3a74>] do_futex+0x2a4/0x17f0 kernel/futex.c:3226
 [<ffffffff812d51b0>] SYSC_futex kernel/futex.c:3286 [inline]
 [<ffffffff812d51b0>] SyS_futex+0x1f0/0x300 kernel/futex.c:3254
 [<ffffffff838cc565>] 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  [<ffffffff814213c5>] unlock_page+0x115/0x150 mm/filemap.c:817
 RSP <ffff8801bb82f7c8>
---[ end trace 30d993a0058dd646 ]---