Re: unregister_netdevice: waiting for DEV to become free (4)

[syzbot]

syzbot has bisected this issue to:

commit 449325b52b7a6208f65ed67d3484fd7b7184477b
Author: Alexei Starovoitov <ast@xxxxxxxxxx>
Date:   Tue May 22 02:22:29 2018 +0000

    umh: introduce fork_usermode_blob() helper

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11f86186900000
start commit:   18445bf4 Merge tag 'spi-fix-v5.9-rc1' of git://git.kernel...
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=13f86186900000
console output: https://syzkaller.appspot.com/x/log.txt?x=15f86186900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bb68b9e8a8cc842f
dashboard link: https://syzkaller.appspot.com/bug?extid=df400f2f24a1677cd7e0
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15859986900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1228fea1900000

Reported-by: syzbot+df400f2f24a1677cd7e0@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 449325b52b7a ("umh: introduce fork_usermode_blob() helper")

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