ima: limit imbalance msg

Limit the number of imbalance messages to once per filesystem type instead of
once per system boot.  (it's actually slightly racy and could give you a
couple per fs, but this isn't a real issue)
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

security/integrity/ima/ima_main.c

@@ -35,6 +35,55 @@ static int __init hash_setup(char *str)
 }
 __setup("ima_hash=", hash_setup);
 
+struct ima_imbalance {
+	struct hlist_node node;
+	unsigned long fsmagic;
+};
+
+/*
+ * ima_limit_imbalance - emit one imbalance message per filesystem type
+ *
+ * Maintain list of filesystem types that do not measure files properly.
+ * Return false if unknown, true if known.
+ */
+static bool ima_limit_imbalance(struct file *file)
+{
+	static DEFINE_SPINLOCK(ima_imbalance_lock);
+	static HLIST_HEAD(ima_imbalance_list);
+
+	struct super_block *sb = file->f_dentry->d_sb;
+	struct ima_imbalance *entry;
+	struct hlist_node *node;
+	bool found = false;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
+		if (entry->fsmagic == sb->s_magic) {
+			found = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	if (found)
+		goto out;
+
+	entry = kmalloc(sizeof(*entry), GFP_NOFS);
+	if (!entry)
+		goto out;
+	entry->fsmagic = sb->s_magic;
+	spin_lock(&ima_imbalance_lock);
+	/*
+	 * we could have raced and something else might have added this fs
+	 * to the list, but we don't really care
+	 */
+	hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
+	spin_unlock(&ima_imbalance_lock);
+	printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
+	       entry->fsmagic);
+out:
+	return found;
+}
+
 /*
  * Update the counts given an fmode_t
  */
@@ -69,15 +118,10 @@ static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
 		}
 	}
 
-	if ((iint->opencount < 0) ||
-	    (iint->readcount < 0) ||
-	    (iint->writecount < 0)) {
-		static int dumped;
-
-		if (dumped)
-			return;
-		dumped = 1;
-
+	if (((iint->opencount < 0) ||
+	     (iint->readcount < 0) ||
+	     (iint->writecount < 0)) &&
+	    !ima_limit_imbalance(file)) {
 		printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
 		       __FUNCTION__, iint->readcount, iint->writecount,
 		       iint->opencount);