linux-kernel - [PATCH 3/7] audit: eliminate string copy for new tree rules

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Date:	Thu,  2 Oct 2014 22:05:20 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	linux-audit@...hat.com, linux-kernel@...r.kernel.org
Cc:	Richard Guy Briggs <rgb@...hat.com>, eparis@...hat.com,
	sgrubb@...hat.com, aviro@...hat.com, pmoore@...hat.com
Subject: [PATCH 3/7] audit: eliminate string copy for new tree rules

New tree rules copy the path twice and discard the intermediary copy.

This saves one pointer at the expense of one path string copy.

Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 kernel/audit_tree.c  |    9 +++++----
 kernel/auditfilter.c |    5 +++--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index bd418c4..ace72ed 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -17,7 +17,7 @@ struct audit_tree {
 	struct list_head list;
 	struct list_head same_root;
 	struct rcu_head head;
-	char pathname[];
+	char *pathname;
 };
 
 struct audit_chunk {
@@ -70,11 +70,11 @@ static LIST_HEAD(prune_list);
 
 static struct fsnotify_group *audit_tree_group;
 
-static struct audit_tree *alloc_tree(const char *s)
+static struct audit_tree *alloc_tree(char *s)
 {
 	struct audit_tree *tree;
 
-	tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL);
+	tree = kmalloc(sizeof(struct audit_tree), GFP_KERNEL);
 	if (tree) {
 		atomic_set(&tree->count, 1);
 		tree->goner = 0;
@@ -83,7 +83,7 @@ static struct audit_tree *alloc_tree(const char *s)
 		INIT_LIST_HEAD(&tree->list);
 		INIT_LIST_HEAD(&tree->same_root);
 		tree->root = NULL;
-		strcpy(tree->pathname, s);
+		tree->pathname = s;
 	}
 	return tree;
 }
@@ -96,6 +96,7 @@ static inline void get_tree(struct audit_tree *tree)
 static inline void put_tree(struct audit_tree *tree)
 {
 	if (atomic_dec_and_test(&tree->count))
+		kfree(tree->pathname);
 		kfree_rcu(tree, head);
 }
 
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index e3378a4..facd704 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -534,9 +534,10 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			entry->rule.buflen += f->val;
 
 			err = audit_make_tree(&entry->rule, str, f->op);
-			kfree(str);
-			if (err)
+			if (err) {
+				kfree(str);
 				goto exit_free;
+			}
 			break;
 		case AUDIT_INODE:
 			err = audit_to_inode(&entry->rule, f);
-- 
1.7.1

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