page:ffffea0007340000 count:2 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000004004(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: 3674 Comm: syz-executor163 Not tainted 4.4.131-g3702e76 #37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cfec8000 task.stack: ffff8801ce428000
RIP: 0010:[<ffffffff8141de15>]  [<ffffffff8141de15>] unlock_page+0x115/0x150 mm/filemap.c:819
RSP: 0018:ffff8801ce42f760  EFLAGS: 00010293
RAX: ffffffff83a6e7c0 RBX: ffffea0007340000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81513249 RDI: ffff8801cfec88dc
RBP: ffff8801ce42f780 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffff8801ce42fa30 R14: ffffea0007341480 R15: ffffea0007340008
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f77e5b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000204a4ff0 CR3: 00000001cfe93000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea0007340000 dffffc0000000000 ffff8801ce42fa30 ffffea0007341480
 ffff8801ce42f868 ffffffff812cc1bc 0000000000000001 ffff8801ce42f818
 0000000000000046 ffff8801cf69b700 00000000cfec88d8 ffff8801ce42fa40
Call Trace:
 [<ffffffff812cc1bc>] get_futex_key+0xadc/0xd80 kernel/futex.c:598
 [<ffffffff812cc999>] futex_wait_setup+0xd9/0x330 kernel/futex.c:2336
 [<ffffffff812cce9f>] futex_wait+0x2af/0x600 kernel/futex.c:2399
 [<ffffffff812d07b2>] do_futex+0x2a2/0x1770 kernel/futex.c:3186
 [<ffffffff812d2789>] C_SYSC_futex kernel/futex_compat.c:200 [inline]
 [<ffffffff812d2789>] compat_SyS_futex+0x1d9/0x2f0 kernel/futex_compat.c:174
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c16aa>] sysenter_flags_fixed+0xd/0x17
Code: e8 48 8d 04 c0 49 8d 3c c6 e8 48 c0 df ff 5b 41 5c 41 5d 41 5e 5d c3 e8 da 33 f3 ff 48 c7 c6 60 aa a9 83 48 89 df e8 4b eb 06 00 <0f> 0b 48 89 df e8 f1 b1 0d 00 e9 0a ff ff ff e8 e7 b1 0d 00 e9 
RIP  [<ffffffff8141de15>] unlock_page+0x115/0x150 mm/filemap.c:819
 RSP <ffff8801ce42f760>
---[ end trace 8a8303cc76faada5 ]---