syzbot has bisected this bug to:
commit 7ddd8faf4399ab4f4edad5604eab35f8a87caf02
Author: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Date: Fri Oct 13 22:57:54 2017 +0000
userfaultfd: selftest: exercise -EEXIST only in background transfer
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=175625c9e00000
start commit: 8f8972a3 Merge tag 'mtd/fixes-for-5.5-rc7' of git://git.ke..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=14d625c9e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=10d625c9e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=adf6c6c2be1c3a718121
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14ea2559e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15ffc8bee00000
Reported-by: syzbot+adf6c6c2be1c3a718121@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 7ddd8faf4399 ("userfaultfd: selftest: exercise -EEXIST only in background transfer")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
