selinux: conditional expression type validation was off-by-one

expr_isvalid() in conditional.c was off-by-one and allowed
invalid expression type COND_LAST. However, it is this header file
that needs to be fixed. That way the if-statement's disjunction's
second component reads more naturally, "if expr type is greater than
the last allowed value" ( rather than using ">=" in conditional.c):

  if (expr->expr_type <= 0 || expr->expr_type > COND_LAST)
Signed-off-by: NVesa-Matti Kari <vmkari@cc.helsinki.fi>
Signed-off-by: NJames Morris <jmorris@namei.org>

security/selinux/ss/conditional.h

@@ -28,7 +28,7 @@ struct cond_expr {
 #define COND_XOR	5 /* bool ^ bool */
 #define COND_EQ		6 /* bool == bool */
 #define COND_NEQ	7 /* bool != bool */
-#define COND_LAST	8
+#define COND_LAST	COND_NEQ
 	__u32 expr_type;
 	__u32 bool;
 	struct cond_expr *next;