ima: limit imbalance msg
Mimi Zohar [Fri, 4 Dec 2009 20:48:40 +0000 (15:48 -0500)]
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

index 16dc57d..a89f44d 100644 (file)
@@ -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);