audit: validate comparison operations, store them in sane form

Don't store the field->op in the messy (and very inconvenient for e.g.
audit_comparator()) form; translate to dense set of values and do full
validation of userland-submitted value while we are at it.

->audit_init_rule() and ->audit_match_rule() get new values now; in-tree
instances updated.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 1b5551d..848212f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2492,7 +2492,7 @@
 	if (field != AUDIT_SUBJ_USER && field != AUDIT_OBJ_USER)
 		return -EINVAL;
 
-	if (op != AUDIT_EQUAL && op != AUDIT_NOT_EQUAL)
+	if (op != Audit_equal && op != Audit_not_equal)
 		return -EINVAL;
 
 	*rule = smk_import(rulestr, 0);
@@ -2556,9 +2556,9 @@
 	 * both pointers will point to the same smack_known
 	 * label.
 	 */
-	if (op == AUDIT_EQUAL)
+	if (op == Audit_equal)
 		return (rule == smack);
-	if (op == AUDIT_NOT_EQUAL)
+	if (op == Audit_not_equal)
 		return (rule != smack);
 
 	return 0;