SCTP: Fix chunk acceptance when no authenticated chunks were listed.

In the case where no autheticated chunks were specified, we were still
trying to verify that a given chunk needs authentication and doing so
incorrectly.  Add a check for parameter length to make sure we don't
try to use an empty auth_chunks parameter to verify against.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/auth.c

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 6d5fa6b..6d89e35 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -631,7 +631,7 @@
 	int found = 0;
 	int i;
 
-	if (!param)
+	if (!param || param->param_hdr.length == 0)
 		return 0;
 
 	len = ntohs(param->param_hdr.length) - sizeof(sctp_paramhdr_t);