netdev - Re: [RFC v2 bpf-next 2/5] bpf: return EOPNOTSUPP when map lookup isn't supported

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Date:   Thu, 4 Oct 2018 18:45:04 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "David S . Miller" <davem@...emloft.net>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        netdev@...r.kernel.org
Subject: Re: [RFC v2 bpf-next 2/5] bpf: return EOPNOTSUPP when map lookup
 isn't supported

On Fri, Oct 05, 2018 at 09:16:04AM +0900, Prashant Bhole wrote:
> 
> 
> On 10/5/2018 9:10 AM, Alexei Starovoitov wrote:
> > On Tue, Oct 02, 2018 at 02:35:16PM +0900, Prashant Bhole wrote:
> > > Return ERR_PTR(-EOPNOTSUPP) from map_lookup_elem() methods of below
> > > map types:
> > > - BPF_MAP_TYPE_PROG_ARRAY
> > > - BPF_MAP_TYPE_STACK_TRACE
> > > - BPF_MAP_TYPE_XSKMAP
> > > - BPF_MAP_TYPE_SOCKMAP/BPF_MAP_TYPE_SOCKHASH
> > > 
> > > Signed-off-by: Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
> > > ---
> > >   kernel/bpf/arraymap.c | 2 +-
> > >   kernel/bpf/sockmap.c  | 2 +-
> > >   kernel/bpf/stackmap.c | 2 +-
> > >   kernel/bpf/xskmap.c   | 2 +-
> > >   4 files changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> > > index dded84cbe814..24583da9ffd1 100644
> > > --- a/kernel/bpf/arraymap.c
> > > +++ b/kernel/bpf/arraymap.c
> > > @@ -449,7 +449,7 @@ static void fd_array_map_free(struct bpf_map *map)
> > >   static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
> > >   {
> > > -	return NULL;
> > > +	return ERR_PTR(-EOPNOTSUPP);
> > 
> > last time we discussed that the verifier should make sure that
> > lookup is not called from bpf program for these map types.
> > I'd like to see test cases in test_verifier.c for these map types
> > to make sure we don't introduce crashes.
> 
> Hi Alexei,
> Patch 05/05 adds such tests in test_verifier.c. Please review those changes.

ahh. missed it. sorry about that. looking...