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Date:   Thu, 12 May 2022 15:51:36 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Eric Dumazet <edumazet@google.com>
Cc:     syzbot <syzbot+8ed8fc4c57e9dcf23ca6@syzkaller.appspotmail.com>,
        David Miller <davem@davemloft.net>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Jiri Pirko <jiri@resnulli.us>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: [syzbot] UBSAN: shift-out-of-bounds in tcf_pedit_init
Message-ID: <20220512155136.70554388@kernel.org>
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On Thu, 12 May 2022 14:19:51 -0700 Eric Dumazet wrote:
> On Thu, May 12, 2022 at 2:18 PM syzbot
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > syzbot can test patches for this issue, for details see:
> > https://goo.gl/tpsmEJ#testing-patches  
> 
> As mentioned earlier, this came with
> 
> commit 8b796475fd7882663a870456466a4fb315cc1bd6
> Author: Paolo Abeni <pabeni@redhat.com>
> Date:   Tue May 10 16:57:34 2022 +0200
> 
>     net/sched: act_pedit: really ensure the skb is writable

Came in as in new stack trace for an old/existing bug, right?
Nothing checks the shift so it'd have already tripped UBSAN 
later on in tcf_pedit_act(), anyway.