sctp: fix the processing for INIT chunk

This patch fixes the problems below:

1. In non-shutdown_ack_sent states: in sctp_sf_do_5_1B_init() and
   sctp_sf_do_5_2_2_dupinit():

  chunk length check should be done before any checks that may cause
  to send abort, as making packet for abort will access the init_tag
  from init_hdr in sctp_ootb_pkt_new().

2. In shutdown_ack_sent state: in sctp_sf_do_9_2_reshutack():

  The same checks as does in sctp_sf_do_5_2_2_dupinit() is needed
  for sctp_sf_do_9_2_reshutack().

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/sctp/sm_statefuns.c

@@ -156,6 +156,12 @@ static enum sctp_disposition __sctp_sf_do_9_1_abort(
 					void *arg,
 					struct sctp_cmd_seq *commands);
 
+static enum sctp_disposition
+__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
+			   const struct sctp_association *asoc,
+			   const union sctp_subtype type, void *arg,
+			   struct sctp_cmd_seq *commands);
+
 /* Small helper function that checks if the chunk length
  * is of the appropriate length.  The 'required_length' argument
  * is set to be the size of a specific chunk we are testing.
@@ -337,6 +343,14 @@ enum sctp_disposition sctp_sf_do_5_1B_init(struct net *net,
 	if (!chunk->singleton)
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
 
+	/* Make sure that the INIT chunk has a valid length.
+	 * Normally, this would cause an ABORT with a Protocol Violation
+	 * error, but since we don't have an association, we'll
+	 * just discard the packet.
+	 */
+	if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
 	/* If the packet is an OOTB packet which is temporarily on the
 	 * control endpoint, respond with an ABORT.
 	 */
@@ -351,14 +365,6 @@ enum sctp_disposition sctp_sf_do_5_1B_init(struct net *net,
 	if (chunk->sctp_hdr->vtag != 0)
 		return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
 
-	/* Make sure that the INIT chunk has a valid length.
-	 * Normally, this would cause an ABORT with a Protocol Violation
-	 * error, but since we don't have an association, we'll
-	 * just discard the packet.
-	 */
-	if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
-		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
-
 	/* If the INIT is coming toward a closing socket, we'll send back
 	 * and ABORT.  Essentially, this catches the race of INIT being
 	 * backloged to the socket at the same time as the user issues close().
@@ -1524,20 +1530,16 @@ static enum sctp_disposition sctp_sf_do_unexpected_init(
 	if (!chunk->singleton)
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
 
+	/* Make sure that the INIT chunk has a valid length. */
+	if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
 	/* 3.1 A packet containing an INIT chunk MUST have a zero Verification
 	 * Tag.
 	 */
 	if (chunk->sctp_hdr->vtag != 0)
 		return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
 
-	/* Make sure that the INIT chunk has a valid length.
-	 * In this case, we generate a protocol violation since we have
-	 * an association established.
-	 */
-	if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
-		return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,
-						  commands);
-
 	if (SCTP_INPUT_CB(chunk->skb)->encap_port != chunk->transport->encap_port)
 		return sctp_sf_new_encap_port(net, ep, asoc, type, arg, commands);
 
@@ -1882,9 +1884,9 @@ static enum sctp_disposition sctp_sf_do_dupcook_a(
 	 * its peer.
 	*/
 	if (sctp_state(asoc, SHUTDOWN_ACK_SENT)) {
-		disposition = sctp_sf_do_9_2_reshutack(net, ep, asoc,
-				SCTP_ST_CHUNK(chunk->chunk_hdr->type),
-				chunk, commands);
+		disposition = __sctp_sf_do_9_2_reshutack(net, ep, asoc,
+							 SCTP_ST_CHUNK(chunk->chunk_hdr->type),
+							 chunk, commands);
 		if (SCTP_DISPOSITION_NOMEM == disposition)
 			goto nomem;
 
@@ -2970,13 +2972,11 @@ enum sctp_disposition sctp_sf_do_9_2_shut_ctsn(
  * that belong to this association, it should discard the INIT chunk and
  * retransmit the SHUTDOWN ACK chunk.
  */
-enum sctp_disposition sctp_sf_do_9_2_reshutack(
-					struct net *net,
-					const struct sctp_endpoint *ep,
-					const struct sctp_association *asoc,
-					const union sctp_subtype type,
-					void *arg,
-					struct sctp_cmd_seq *commands)
+static enum sctp_disposition
+__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
+			   const struct sctp_association *asoc,
+			   const union sctp_subtype type, void *arg,
+			   struct sctp_cmd_seq *commands)
 {
 	struct sctp_chunk *chunk = arg;
 	struct sctp_chunk *reply;
@@ -3010,6 +3010,26 @@ nomem:
 	return SCTP_DISPOSITION_NOMEM;
 }
 
+enum sctp_disposition
+sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep,
+			 const struct sctp_association *asoc,
+			 const union sctp_subtype type, void *arg,
+			 struct sctp_cmd_seq *commands)
+{
+	struct sctp_chunk *chunk = arg;
+
+	if (!chunk->singleton)
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
+	if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk)))
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
+	if (chunk->sctp_hdr->vtag != 0)
+		return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
+
+	return __sctp_sf_do_9_2_reshutack(net, ep, asoc, type, arg, commands);
+}
+
 /*
  * sctp_sf_do_ecn_cwr
  *