Re: [syzbot] UBSAN: shift-out-of-bounds in tcf_pedit_init

[syzbot]

syzbot has bisected this issue to:

commit 8b796475fd7882663a870456466a4fb315cc1bd6
Author: Paolo Abeni <pabeni@xxxxxxxxxx>
Date:   Tue May 10 14:57:34 2022 +0000

    net/sched: act_pedit: really ensure the skb is writable

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=158d3969f00000
start commit:   810c2f0a3f86 mlxsw: Avoid warning during ip6gre device rem..
git tree:       net
final oops:     https://syzkaller.appspot.com/x/report.txt?x=178d3969f00000
console output: https://syzkaller.appspot.com/x/log.txt?x=138d3969f00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=331feb185f8828e0
dashboard link: https://syzkaller.appspot.com/bug?extid=8ed8fc4c57e9dcf23ca6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104e9749f00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15f913b9f00000

Reported-by: syzbot+8ed8fc4c57e9dcf23ca6@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 8b796475fd78 ("net/sched: act_pedit: really ensure the skb is writable")

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