page:ffffea00071e8000 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: 3843 Comm: syz-executor947 Not tainted 4.4.128-gbd23e3a #19
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b6c4c800 task.stack: ffff8801d9938000
RIP: 0010:[<ffffffff8141df45>]  [<ffffffff8141df45>] unlock_page+0x115/0x150 mm/filemap.c:819
RSP: 0018:ffff8801d993f760  EFLAGS: 00010293
RAX: ffffffff83a6e7c0 RBX: ffffea00071e8000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815130e9 RDI: ffff8800b6c4d0dc
RBP: ffff8801d993f780 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffff8801d993fa30 R14: ffffea00071e9480 R15: ffffea00071e8008
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f7754b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000204a4ff0 CR3: 00000001d9438000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffea00071e8000 dffffc0000000000 ffff8801d993fa30 ffffea00071e9480
 ffff8801d993f868 ffffffff812cc19c 0000000000000001 ffff8801d993f818
 0000000000000046 ffff8801cf317700 00000000b6c4d0d8 ffff8801d993fa40
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
 [<ffffffff812d2769>] C_SYSC_futex kernel/futex_compat.c:200 [inline]
 [<ffffffff812d2769>] 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
 [<ffffffff838c00aa>] sysenter_flags_fixed+0xd/0x17
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 <ffff8801d993f760>
---[ end trace e0294567e29ddfd6 ]---