sctp: Fix memory leak in sctp_sf_do_5_2_4_dupcook

In the implementation of sctp_sf_do_5_2_4_dupcook() the allocated
new_asoc is leaked if security_sctp_assoc_request() fails. Release it
via sctp_association_free().

Fixes: 2277c7c ("sctp: Add LSM hooks")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

net/sctp/sm_statefuns.c

@@ -2160,8 +2160,10 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
 
 	/* Update socket peer label if first association. */
 	if (security_sctp_assoc_request((struct sctp_endpoint *)ep,
-					chunk->skb))
+					chunk->skb)) {
+		sctp_association_free(new_asoc);
 		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+	}
 
 	/* Set temp so that it won't be added into hashtable */
 	new_asoc->temp = 1;