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

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Wed, 26 Aug 2015 17:59:25 -0300

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.

Thanks,
Marcelo

> >  		case SCTP_PARAM_IPV6_ADDRESS:
> > +			if (addr_param_seen)
> > +				return false;
> >  			if (length != sizeof(sctp_ipv6addr_param_t))
> >  				return false;
> > -			addr_param_seen = true;
> > +			if (param.v == addip->addip_hdr.params)
> > +				addr_param_seen = true;
> >  			break;
> >  		case SCTP_PARAM_ADD_IP:
> >  		case SCTP_PARAM_DEL_IP:
> > 
>