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>

1 files changed, 50 insertions, 0 deletions

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index caed19d90d06..a583d67cab63 100644
--- a/net/sctp/sm_statefuns.c
+++ b/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.
  *