ima: differentiate appraise status only for hook specific rules

Different hooks can require different methods for appraising a
file's integrity. As a result, an integrity appraisal status is
cached on a per hook basis.

Only a hook specific rule, requires the inode to be re-appraised.
This patch eliminates unnecessary appraisals.

Signed-off-by: Mimi Zohar <[e-mail]>
Signed-off-by: Dmitry Kasatkin <[e-mail]>

security/integrity/ima/ima_main.c

···
 	struct integrity_iint_cache *iint;
 	char *pathbuf = NULL;
 	const char *pathname = NULL;
-	int rc = -ENOMEM, action, must_appraise;
+	int rc = -ENOMEM, action, must_appraise, _func;
 
 	if (!ima_initialized || !S_ISREG(inode->i_mode))
 		return 0;
···
 		return 0;
 
 	must_appraise = action & IMA_APPRAISE;
+
+	/*  Is the appraise rule hook specific?  */
+	_func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
 
 	mutex_lock(&inode->i_mutex);
 
···
 	/* Nothing to do, just return existing appraised status */
 	if (!action) {
 		if (must_appraise)
-			rc = ima_get_cache_status(iint, function);
+			rc = ima_get_cache_status(iint, _func);
 		goto out_digsig;
 	}
 
···
 	if (action & IMA_MEASURE)
 		ima_store_measurement(iint, file, pathname);
 	if (action & IMA_APPRAISE_SUBMASK)
-		rc = ima_appraise_measurement(function, iint, file, pathname);
+		rc = ima_appraise_measurement(_func, iint, file, pathname);
 	if (action & IMA_AUDIT)
 		ima_audit_measurement(iint, pathname);
 	kfree(pathbuf);

security/integrity/ima/ima_policy.c

···
 
 /*
  * In addition to knowing that we need to appraise the file in general,
- * we need to differentiate between calling hooks.
+ * we need to differentiate between calling hooks, for hook specific rules.
  */
-static int get_subaction(int func)
+static int get_subaction(struct ima_rule_entry *rule, int func)
 {
+	if (!(rule->flags & IMA_FUNC))
+		return IMA_FILE_APPRAISE;
+
 	switch(func) {
 	case MMAP_CHECK:
 		return IMA_MMAP_APPRAISE;
···
 
 		action |= entry->action & IMA_DO_MASK;
 		if (entry->action & IMA_APPRAISE)
-			action |= get_subaction(func);
+			action |= get_subaction(entry, func);
 
 		if (entry->action & IMA_DO_MASK)
 			actmask &= ~(entry->action | entry->action << 1);