Subject: Re: [PATCH net v3] sctp: asconf's process should verify address parameter is in the beginning

From: Vlad Yasevich <[email-masked]>
Date: Wed, 26 Aug 2015 17:37:16 -0400

On 08/26/2015 05:09 PM, lucien xin wrote:
> On Thu, Aug 27, 2015 at 4:59 AM, Marcelo Ricardo Leitner
> <[email-masked]> wrote:
>> On Wed, Aug 26, 2015 at 04:42:21PM -0400, Vlad Yasevich wrote:
>>> On 08/26/2015 04:35 PM, Xin Long wrote:
>>>> in sctp_process_asconf(), we get address parameter from the beginning of
>>>> the addip params. but we never check if it's really there. if the addr
>>>> param is not there, it still can pass sctp_verify_asconf(), then to be
>>>> handled by sctp_process_asconf(), it will not be safe.
>>>>
>>>> so add a code in sctp_verify_asconf() to check the address parameter is in
>>>> the beginning, or return false to send abort.
>>>>
>>>> v2->v3:
>>>>  * put the check in the loop, add the check for multiple address parameters.
>>>
>>>
>>> Please split the multiple address detection from first address detection.
>>> They are 2 different bugs and each one deserves a separate commit and
>>> changelog.
>>
>> See below, thx.
>>
>>>
>>> Thanks
>>> -vlad
>>>
>>>> v1->v2:
>>>>  * put the check behind the params' length verify.
>>>>
>>>> Signed-off-by: Xin Long <[email-masked]>
>>>> Signed-off-by: Vlad Yasevich <[email-masked]>
>>>> ---
>>>>  net/sctp/sm_make_chunk.c | 14 ++++++++++++--
>>>>  1 file changed, 12 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
>>>> index 06320c8..4068fe1 100644
>>>> --- a/net/sctp/sm_make_chunk.c
>>>> +++ b/net/sctp/sm_make_chunk.c
>>>> @@ -3130,14 +3130,24 @@ bool sctp_verify_asconf(const struct sctp_association *asoc,
>>>>             case SCTP_PARAM_ERR_CAUSE:
>>>>                     break;
>>>>             case SCTP_PARAM_IPV4_ADDRESS:
>>>> +                   if (addr_param_seen) {
>>>> +                           /* peer placed multiple address parameters into
>>>> +                            * the same asconf. reject it.
>>>> +                            */
>>>> +                           return false;
>>>> +                   }
>>>>                     if (length != sizeof(sctp_ipv4addr_param_t))
>>>>                             return false;
>>>> -                   addr_param_seen = true;
>>>> +                   if (param.v == addip->addip_hdr.params)
>>>> +                           addr_param_seen = true;
>>>>                     break;
>>
>> I know I had suggested using addr_param_seen to check for multiple
>> occurrences, but now realized we can simplify this with something like:
>>
>> +                       if (param.v != addip->addip_hdr.params)
>> +                               return false;
>>                         addr_param_seen = true;
>>
>> Then the check against addr_param_seen is not needed and do both checks
>> at once.
>>
> looks nice, Vlad ?
> 

yes.  This is fine too.  I think this kills 2 bugs with 1 patch...

If you go this route, make sure to document this well in the change log.

-vlad