netdev - Re: [PATCH bpf v2 1/3] xdp: check prog type before updating BPF link

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Message-ID: <CAADnVQLBDwUEcf63Jd2ohe0k5xKAcFaUmPL6tC-h937pSTzcCg@mail.gmail.com>
Date:   Sat, 8 Jan 2022 11:37:06 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        syzbot <syzbot+983941aa85af6ded1fd9@...kaller.appspotmail.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf v2 1/3] xdp: check prog type before updating BPF link

On Fri, Jan 7, 2022 at 2:11 PM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> The bpf_xdp_link_update() function didn't check the program type before
> updating the program, which made it possible to install any program type as
> an XDP program, which is obviously not good. Syzbot managed to trigger this
> by swapping in an LWT program on the XDP hook which would crash in a helper
> call.
>
> Fix this by adding a check and bailing out if the types don't match.
>
> Fixes: 026a4c28e1db ("bpf, xdp: Implement LINK_UPDATE for BPF XDP link")
> Reported-by: syzbot+983941aa85af6ded1fd9@...kaller.appspotmail.com
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>

Thanks a lot for the quick fix!
The merge window is about to begin.
We will land it as soon as possible when bpf tree will be ready
to accept fixes.