SCTP : Add paramters validity check for ASCONF chunk

If ADDIP is enabled, when an ASCONF chunk is received with ASCONF
paramter length set to zero, this will cause infinite loop.
By the way, if an malformed ASCONF chunk is received, will cause
processing to access memory without verifying.

This is because of not check the validity of parameters in ASCONF chunk.
This patch fixed this.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

include/net/sctp/sm.h

@@ -246,6 +246,9 @@ struct sctp_chunk *sctp_make_asconf_update_ip(struct sctp_association *,
 					      int, __be16);
 struct sctp_chunk *sctp_make_asconf_set_prim(struct sctp_association *asoc,
 					     union sctp_addr *addr);
+int sctp_verify_asconf(const struct sctp_association *asoc,
+		       struct sctp_paramhdr *param_hdr, void *chunk_end,
+		       struct sctp_paramhdr **errp);
 struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
 				       struct sctp_chunk *asconf);
 int sctp_process_asconf_ack(struct sctp_association *asoc,

include/net/sctp/structs.h

@@ -421,6 +421,7 @@ struct sctp_signed_cookie {
  * internally.
  */
 union sctp_addr_param {
+	struct sctp_paramhdr p;
 	struct sctp_ipv4addr_param v4;
 	struct sctp_ipv6addr_param v6;
 };

net/sctp/sm_make_chunk.c

@@ -2499,6 +2499,52 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
 	return SCTP_ERROR_NO_ERROR;
 }
 
+/* Verify the ASCONF packet before we process it.  */
+int sctp_verify_asconf(const struct sctp_association *asoc,
+		       struct sctp_paramhdr *param_hdr, void *chunk_end,
+		       struct sctp_paramhdr **errp) {
+	sctp_addip_param_t *asconf_param;
+	union sctp_params param;
+	int length, plen;
+
+	param.v = (sctp_paramhdr_t *) param_hdr;
+	while (param.v <= chunk_end - sizeof(sctp_paramhdr_t)) {
+		length = ntohs(param.p->length);
+		*errp = param.p;
+
+		if (param.v > chunk_end - length ||
+		    length < sizeof(sctp_paramhdr_t))
+			return 0;
+
+		switch (param.p->type) {
+		case SCTP_PARAM_ADD_IP:
+		case SCTP_PARAM_DEL_IP:
+		case SCTP_PARAM_SET_PRIMARY:
+			asconf_param = (sctp_addip_param_t *)param.v;
+			plen = ntohs(asconf_param->param_hdr.length);
+			if (plen < sizeof(sctp_addip_param_t) +
+			    sizeof(sctp_paramhdr_t))
+				return 0;
+			break;
+		case SCTP_PARAM_SUCCESS_REPORT:
+		case SCTP_PARAM_ADAPTATION_LAYER_IND:
+			if (length != sizeof(sctp_addip_param_t))
+				return 0;
+
+			break;
+		default:
+			break;
+		}
+
+		param.v += WORD_ROUND(length);
+	}
+
+	if (param.v != chunk_end)
+		return 0;
+
+	return 1;
+}
+
 /* Process an incoming ASCONF chunk with the next expected serial no. and
  * return an ASCONF_ACK chunk to be sent in response.
  */

net/sctp/sm_statefuns.c

@@ -117,6 +117,13 @@ static sctp_disposition_t sctp_sf_violation_chunklen(
 				     void *arg,
 				     sctp_cmd_seq_t *commands);
 
+static sctp_disposition_t sctp_sf_violation_paramlen(
+				     const struct sctp_endpoint *ep,
+				     const struct sctp_association *asoc,
+				     const sctp_subtype_t type,
+				     void *arg,
+				     sctp_cmd_seq_t *commands);
+
 static sctp_disposition_t sctp_sf_violation_ctsn(
 				     const struct sctp_endpoint *ep,
 				     const struct sctp_association *asoc,
@@ -3296,8 +3303,11 @@ sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
 {
 	struct sctp_chunk	*chunk = arg;
 	struct sctp_chunk	*asconf_ack = NULL;
+	struct sctp_paramhdr	*err_param = NULL;
 	sctp_addiphdr_t		*hdr;
+	union sctp_addr_param	*addr_param;
 	__u32			serial;
+	int			length;
 
 	if (!sctp_vtag_verify(chunk, asoc)) {
 		sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
@@ -3313,6 +3323,20 @@ sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
 	hdr = (sctp_addiphdr_t *)chunk->skb->data;
 	serial = ntohl(hdr->serial);
 
+	addr_param = (union sctp_addr_param *)hdr->params;
+	length = ntohs(addr_param->p.length);
+	if (length < sizeof(sctp_paramhdr_t))
+		return sctp_sf_violation_paramlen(ep, asoc, type,
+			   (void *)addr_param, commands);
+
+	/* Verify the ASCONF chunk before processing it. */
+	if (!sctp_verify_asconf(asoc,
+	    (sctp_paramhdr_t *)((void *)addr_param + length),
+	    (void *)chunk->chunk_end,
+	    &err_param))
+		return sctp_sf_violation_paramlen(ep, asoc, type,
+			   (void *)&err_param, commands);
+
 	/* ADDIP 4.2 C1) Compare the value of the serial number to the value
 	 * the endpoint stored in a new association variable
 	 * 'Peer-Serial-Number'.
@@ -3367,6 +3391,7 @@ sctp_disposition_t sctp_sf_do_asconf_ack(const struct sctp_endpoint *ep,
 	struct sctp_chunk	*asconf_ack = arg;
 	struct sctp_chunk	*last_asconf = asoc->addip_last_asconf;
 	struct sctp_chunk	*abort;
+	struct sctp_paramhdr	*err_param = NULL;
 	sctp_addiphdr_t		*addip_hdr;
 	__u32			sent_serial, rcvd_serial;
 
@@ -3384,6 +3409,14 @@ sctp_disposition_t sctp_sf_do_asconf_ack(const struct sctp_endpoint *ep,
 	addip_hdr = (sctp_addiphdr_t *)asconf_ack->skb->data;
 	rcvd_serial = ntohl(addip_hdr->serial);
 
+	/* Verify the ASCONF-ACK chunk before processing it. */
+	if (!sctp_verify_asconf(asoc,
+	    (sctp_paramhdr_t *)addip_hdr->params,
+	    (void *)asconf_ack->chunk_end,
+	    &err_param))
+		return sctp_sf_violation_paramlen(ep, asoc, type,
+			   (void *)&err_param, commands);
+
 	if (last_asconf) {
 		addip_hdr = (sctp_addiphdr_t *)last_asconf->subh.addip_hdr;
 		sent_serial = ntohl(addip_hdr->serial);
@@ -3870,6 +3903,23 @@ static sctp_disposition_t sctp_sf_violation_chunklen(
 					sizeof(err_str));
 }
 
+/*
+ * Handle a protocol violation when the parameter length is invalid.
+ * "Invalid" length is identified as smaller then the minimal length a
+ * given parameter can be.
+ */
+static sctp_disposition_t sctp_sf_violation_paramlen(
+				     const struct sctp_endpoint *ep,
+				     const struct sctp_association *asoc,
+				     const sctp_subtype_t type,
+				     void *arg,
+				     sctp_cmd_seq_t *commands) {
+	char err_str[] = "The following parameter had invalid length:";
+
+	return sctp_sf_abort_violation(ep, asoc, arg, commands, err_str,
+					sizeof(err_str));
+}
+
 /* Handle a protocol violation when the peer trying to advance the
  * cumulative tsn ack to a point beyond the max tsn currently sent.
  *