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

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Date:   Fri, 5 Oct 2018 09:16:04 +0900
From:   Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
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 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. Thank you.

-Prashant