syzbot has bisected this issue to:

commit 5a781ccbd19e4664babcbe4b4ead7aa2b9283d22
Author: Vinicius Costa Gomes [off-list ref]
Date:   Sat Sep 29 00:59:43 2018 +0000

    tc: Add support for configuring the taprio scheduler

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16d46e1b100000
start commit:   7cc2a8ea Merge tag 'block-5.8-2020-07-01' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d46e1b100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7be693511b29b338
dashboard link: https://syzkaller.appspot.com/bug?extid=0fb70e87d8e0ac278fe9
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1023588f100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1647a88f100000

Reported-by: syzbot+0fb70e87d8e0ac278fe9@syzkaller.appspotmail.com
Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio scheduler")

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