WARNING in untrack_pfn (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 62872f95 Merge 4.4.174 into android-4.4
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=130255bd200000
kernel config: https://syzkaller.appspot.com/x/.config?x=47bc4dd423780c4a
dashboard link: https://syzkaller.appspot.com/bug?extid=a3ec2d79ea91b53b171f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=165f6017200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=163578df200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3ec2d...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 2085 at arch/x86/mm/pat.c:1017 untrack_pfn+0x214/0x270
arch/x86/mm/pat.c:1017()
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 2085 Comm: syz-executor338 Not tainted 4.4.174+ #4
0000000000000000 2349228cc06b04e7 ffff8800b6a6f7b8 ffffffff81aad1a1
0000000000000000 ffffffff82835ee0 ffffffff82831440 00000000000003f9
ffffffff810b6b24 ffff8800b6a6f898 ffffffff813a48c2 0000000041b58ab3
Call Trace:
[<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
[<ffffffff813a48c2>] panic+0x1b9/0x37b kernel/panic.c:112
[<ffffffff813a4ab9>] warn_slowpath_common kernel/panic.c:455 [inline]
[<ffffffff813a4ab9>] warn_slowpath_common.cold+0x20/0x20 kernel/panic.c:435
[<ffffffff810d3aaa>] warn_slowpath_null+0x2a/0x30 kernel/panic.c:492
[<ffffffff810b6b24>] untrack_pfn+0x214/0x270 arch/x86/mm/pat.c:1017
[<ffffffff8143315e>] unmap_single_vma+0xe2e/0x1090 mm/memory.c:1322
[<ffffffff81434d28>] unmap_vmas+0x48/0xa0 mm/memory.c:1373
[<ffffffff81441689>] unmap_region+0x1a9/0x320 mm/mmap.c:2499
[<ffffffff814455ba>] do_munmap+0x4ca/0xcf0 mm/mmap.c:2696
[<ffffffff81450e2e>] move_vma+0x50e/0x920 mm/mremap.c:334
[<ffffffff81451c1d>] mremap_to mm/mremap.c:453 [inline]
[<ffffffff81451c1d>] SYSC_mremap mm/mremap.c:516 [inline]
[<ffffffff81451c1d>] SyS_mremap+0x9dd/0xd60 mm/mremap.c:483
[<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Kernel Offset: disabled
Rebooting in 86400 seconds..


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