syzbot suspects this issue was fixed by commit:

commit 15a8d68e9dc23dc9def4bd7e9563db60f4f86580
Author: Wei Yang [off-list ref]
Date:   Tue Oct 13 23:56:33 2020 +0000

    mm/hugetlb: a page from buddy is not on any list

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13612350d00000
start commit:   1590a2e1 Merge tag 'acpi-5.8-rc3' of git://git.kernel.org/..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=18a1619cceea30ed45af
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10c79dbb100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=169bba3d100000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: mm/hugetlb: a page from buddy is not on any list

For information about bisection process see: https://goo.gl/tpsmEJ#bisection