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References: <20210524185054.65642-1-george.mccollister@gmail.com> <20210524212938.jaepbj5qdl3esd4i@skbuf>
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From:   George McCollister <george.mccollister@gmail.com>
Date:   Tue, 25 May 2021 16:46:21 -0500
Message-ID: <CAFSKS=Mdvsqo0KUqTMdRgJMQ1SSa45wYJ_YM=rqnFEFJBoxZHw@mail.gmail.com>
Subject: Re: [PATCH net] net: hsr: fix mac_len checks
To:     Vladimir Oltean <olteanv@gmail.com>
Cc:     netdev <netdev@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Murali Karicheri <m-karicheri2@ti.com>,
        Taehee Yoo <ap420073@gmail.com>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Wang Hai <wanghai38@huawei.com>,
        Phillip Potter <phil@philpotter.co.uk>,
        Andreas Oetken <andreas.oetken@siemens.com>,
        Marco Wenzel <marco.wenzel@a-eberle.de>,
        open list <linux-kernel@vger.kernel.org>
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On Mon, May 24, 2021 at 4:29 PM Vladimir Oltean <olteanv@gmail.com> wrote:
[snip]
> > +     ret = hsr->proto_ops->fill_frame_info(proto, skb, frame);
>
> Nitpick: hsr uses "res", not "ret".
>

Oops. I'll try to pay more attention to what is used in the existing
code next time.

[snip]
>
> I admit that I went through both patches and I still don't understand
> what is the code path that the original commit 2e9f60932a2c ("net: hsr:
> check skb can contain struct hsr_ethhdr in fill_frame_info") is
> protecting against. I ran the C reproducer linked by syzbot too and I
> did not reproduce it (I did not compile with the linked clang though).

I think it's complaining if you access more than mac_len bytes from
the pointer returned by skb_mac_header() but I'm not familiar with
this bot.

Thanks for testing the patch.

-George