Always initialize scontext and scontext_len

Always initialize *scontext and *scontext_len in security_sid_to_context.

(via http://lkml.org/lkml/2007/2/23/135)

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/ss/services.c

@@ -609,6 +609,9 @@ int security_sid_to_context(u32 sid, char **scontext, u32 *scontext_len)
 	struct context *context;
 	int rc = 0;
 
+	*scontext = NULL;
+	*scontext_len  = 0;
+
 	if (!ss_initialized) {
 		if (sid <= SECINITSID_NUM) {
 			char *scontextp;