[PATCH v2 4/4] ima: differentiate appraise status only for hook specific rules

[Mimi Zohar]

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 <zohar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
---
 security/integrity/ima/ima_main.c   | 9 ++++++---
 security/integrity/ima/ima_policy.c | 9 ++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 66b7f40..3e751a9 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -146,7 +146,7 @@ static int process_measurement(struct file *file, const char *filename,
 	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;
@@ -161,6 +161,9 @@ static int process_measurement(struct file *file, const char *filename,
 
 	must_appraise = action & IMA_APPRAISE;
 
+	/*  Is the appraise rule hook specific?  */
+	_func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
+
 	mutex_lock(&inode->i_mutex);
 
 	iint = integrity_inode_get(inode);
@@ -178,7 +181,7 @@ static int process_measurement(struct file *file, const char *filename,
 	/* 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;
 	}
 
@@ -195,7 +198,7 @@ static int process_measurement(struct file *file, const char *filename,
 	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);
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 4d7c0ae..4adcd0f 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -220,10 +220,13 @@ retry:
 
 /*
  * 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;
@@ -268,7 +271,7 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
 
 		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);
-- 
1.8.1.rc3

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