netdev - Re: [Potential Spoof] [PATCH bpf-next] selftest/bpf: fix compilation warning in sockmap_parse

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Message-ID: <CAEf4BzZ5htm+SV9aJpa8fkzQ2LSgoWZLFTK-AOSMj6r-70mXEg@mail.gmail.com>
Date:   Fri, 13 Mar 2020 16:58:50 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [Potential Spoof] [PATCH bpf-next] selftest/bpf: fix compilation
 warning in sockmap_parse_prog.c

On Fri, Mar 13, 2020 at 4:53 PM Martin KaFai Lau <kafai@...com> wrote:
>
> On Fri, Mar 13, 2020 at 04:07:15PM -0700, Andrii Nakryiko wrote:
> > Cast void * to long before casting to 32-bit __u32 to avoid compilation
> > warning.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> >  tools/testing/selftests/bpf/progs/sockmap_parse_prog.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c b/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c
> > index a5c6d5903b22..a9c2bdbd841e 100644
> > --- a/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c
> > +++ b/tools/testing/selftests/bpf/progs/sockmap_parse_prog.c
> > @@ -12,7 +12,7 @@ int bpf_prog1(struct __sk_buff *skb)
> >       __u32 lport = skb->local_port;
> >       __u32 rport = skb->remote_port;
> >       __u8 *d = data;
> > -     __u32 len = (__u32) data_end - (__u32) data;
> I think this line can be removed.  "len" is not used.

hm... never checked that, I assumed compiler will emit warning about
unused variable... v2 without this line is coming...

>
> > +     __u32 len = (__u32)(long)data_end - (__u32)(long)data;
>
> >       int err;
> >
> >       if (data + 10 > data_end) {
> > --
> > 2.17.1
> >