linux-kernel - Re: [PATCH bpf] xdp: use trusted arguments in XDP hints kfuncs

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Message-ID: <CAADnVQ+Peos-Y08_h27EYf=cO8ewdNwf-T0mmHvcEREv9+C04Q@mail.gmail.com>
Date:   Tue, 11 Jul 2023 20:06:38 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        bpf <bpf@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        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>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Martin KaFai Lau <martin.lau@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] xdp: use trusted arguments in XDP hints kfuncs

On Tue, Jul 11, 2023 at 10:00 AM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> On Tue, Jul 11, 2023 at 7:21 AM Jesper Dangaard Brouer
> <jbrouer@...hat.com> wrote:
> >
> >
> > On 11/07/2023 12.59, Larysa Zaremba wrote:
> > > Currently, verifier does not reject XDP programs that pass NULL pointer to
> > > hints functions. At the same time, this case is not handled in any driver
> > > implementation (including veth). For example, changing
> > >
> > > bpf_xdp_metadata_rx_timestamp(ctx, &timestamp);
> > >
> > > to
> > >
> > > bpf_xdp_metadata_rx_timestamp(ctx, NULL);
> > >
> > > in xdp_metadata test successfully crashes the system.
> > >
> > > Add KF_TRUSTED_ARGS flag to hints kfunc definitions, so driver code
> > > does not have to worry about getting invalid pointers.
> > >
> >
> > Looks good to me, assuming this means verifier will reject BPF-prog's
> > supplying NULL.
> >
> > Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>
> >
> > > Fixes: 3d76a4d3d4e5 ("bpf: XDP metadata RX kfuncs")
> > > Reported-by: Stanislav Fomichev <sdf@...gle.com>
> > > Closes: https://lore.kernel.org/bpf/ZKWo0BbpLfkZHbyE@google.com/
> > > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
>
> Acked-by: Stanislav Fomichev <sdf@...gle.com>
>
> Thank you for the fix!

Applied. Thanks