syzbot has bisected this bug to:

commit 77cd0d7b3f257fd0e3096b4fdcff1a7d38e99e10
Author: Magnus Karlsson [off-list ref]
Date:   Wed Aug 14 07:27:17 2019 +0000

     xsk: add support for need_wakeup flag in AF_XDP rings

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17848acd600000
start commit:   a3c0e7b1 Merge tag 'libnvdimm-fixes-5.4-rc1' of git://git...
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=14448acd600000
console output: https://syzkaller.appspot.com/x/log.txt?x=10448acd600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ffbfa7e4a36190f
dashboard link: https://syzkaller.appspot.com/bug?extid=a5765ed8cdb1cca4d249
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1096d835600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=129f15f3600000

Reported-by: syzbot+a5765ed8cdb1cca4d249@syzkaller.appspotmail.com
Fixes: 77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP  
rings")

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