page:ffffea0002c08000 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:819!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3735 Comm: syz-executor374 Not tainted 4.4.128-gbd23e3a #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801ce31c800 task.stack: ffff8801cc9f0000
RIP: 0010:[<ffffffff8141df45>]  [<ffffffff8141df45>] unlock_page+0x115/0x150 mm/filemap.c:819
RSP: 0018:ffff8801cc9f77d8  EFLAGS: 00010293
RAX: ffffffff83a6e7c0 RBX: ffffea0002c08000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815130e9 RDI: ffff8801ce31d0dc
RBP: ffff8801cc9f77f8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffff8801cc9f7aa8 R14: ffffea0002c09480 R15: ffffea0002c08008
FS:  00007f9f05431700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000204a4ff0 CR3: 00000001cdf5a000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea0002c08000 dffffc0000000000 ffff8801cc9f7aa8 ffffea0002c09480
 ffff8801cc9f78e0 ffffffff812cc19c 0000000000000001 ffff8801cc9f7890
 0000000000000046 ffff8801ce38d400 00000000ce31d0d8 ffff8801cc9f7ab8
Call Trace:
 [<ffffffff812cc19c>] get_futex_key+0xadc/0xd80 kernel/futex.c:598
 [<ffffffff812cc979>] futex_wait_setup+0xd9/0x330 kernel/futex.c:2336
 [<ffffffff812cce7f>] futex_wait+0x2af/0x600 kernel/futex.c:2399
 [<ffffffff812d0792>] do_futex+0x2a2/0x1770 kernel/futex.c:3186
 [<ffffffff812d1e50>] SYSC_futex kernel/futex.c:3246 [inline]
 [<ffffffff812d1e50>] SyS_futex+0x1f0/0x300 kernel/futex.c:3214
 [<ffffffff838be765>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: e8 48 8d 04 c0 49 8d 3c c6 e8 f8 be df ff 5b 41 5c 41 5d 41 5e 5d c3 e8 8a 32 f3 ff 48 c7 c6 60 aa a9 83 48 89 df e8 4b eb 06 00 <0f> 0b 48 89 df e8 61 af 0d 00 e9 0a ff ff ff e8 57 af 0d 00 e9 
RIP  [<ffffffff8141df45>] unlock_page+0x115/0x150 mm/filemap.c:819
 RSP <ffff8801cc9f77d8>
---[ end trace b285b0261934edaa ]---