Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210716100452.113652-1-lmb@cloudflare.com> <CAEf4BzauzWhNag0z31krN_MTZTGLynAJvkh_7P3yLQCx5XLTAg@mail.gmail.com>
In-Reply-To: <CAEf4BzauzWhNag0z31krN_MTZTGLynAJvkh_7P3yLQCx5XLTAg@mail.gmail.com>
From:   Lorenz Bauer <lmb@cloudflare.com>
Date:   Mon, 19 Jul 2021 09:45:16 +0100
Message-ID: <CACAyw98RaF8SgA9nkduXo-wBdsRN86cP=seX9d83i0Qhi0gbeQ@mail.gmail.com>
Subject: Re: [PATCH bpf] bpf: fix OOB read when printing XDP link fdinfo
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        kernel-team <kernel-team@cloudflare.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, 16 Jul 2021 at 21:44, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> Well, oops. Thanks for the fix!
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
>
> It would be great to have a compilation error for something like this.
> I wonder if we can do something to detect this going forward?

I had a second patch that introduced MAX_BPF_LINK_TYPE, etc. and then
added explicit array initializers:

     [MAX_BPF_LINK_TYPE] = NULL,

That turns the OOB read into a NULL read. But it has to be done for
every inclusion of bpf_types.h so it's
a bit cumbersome. Maybe add MAX_BPF_LINK_TYPE and then add an entry in
bpf_types.h for it as well?

--
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

www.cloudflare.com