security: call security_sctp_assoc_request in sctp_sf_do_5_1D_ce

The asoc created when receives the INIT chunk is a temporary one, it
will be deleted after INIT_ACK chunk is replied. So for the real asoc
created in sctp_sf_do_5_1D_ce() when the COOKIE_ECHO chunk is received,
security_sctp_assoc_request() should also be called.

v1->v2:
  - fix some typo and grammar errors, noticed by Ondrej.

Fixes: 72e89f50 ("security: Add support for SCTP security hooks")
Reported-by: Prashanth Prahlad <pprahlad@redhat.com>
Reviewed-by: Richard Haines <richard_c_haines@btinternet.com>
Tested-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/security/SCTP.rst

@@ -151,9 +151,9 @@ establishing an association.
          INIT --------------------------------------------->
                                                    sctp_sf_do_5_1B_init()
                                                  Respond to an INIT chunk.
-                                             SCTP peer endpoint "A" is
-                                             asking for an association. Call
-                                             security_sctp_assoc_request()
+                                             SCTP peer endpoint "A" is asking
+                                             for a temporary association.
+                                             Call security_sctp_assoc_request()
                                              to set the peer label if first
                                              association.
                                              If not first association, check
@@ -163,9 +163,12 @@ establishing an association.
           |                                       discard the packet.
           |
     COOKIE ECHO ------------------------------------------>
-                                                          |
-                                                          |
-                                                          |
+                                                  sctp_sf_do_5_1D_ce()
+                                             Respond to an COOKIE ECHO chunk.
+                                             Confirm the cookie and create a
+                                             permanent association.
+                                             Call security_sctp_assoc_request() to
+                                             do the same as for INIT chunk Response.
           <------------------------------------------- COOKIE ACK
           |                                               |
     sctp_sf_do_5_1E_ca                                    |

net/sctp/sm_statefuns.c

@@ -781,6 +781,11 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
 		}
 	}
 
+	if (security_sctp_assoc_request(new_asoc, chunk->skb)) {
+		sctp_association_free(new_asoc);
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+	}
+
 	/* Delay state machine commands until later.
 	 *
 	 * Re-build the bind address for the association is done in