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>

1 files changed, 53 insertions, 9 deletions

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 16dc57d247d0..a89f44d5e030 100644
--- a/security/integrity/ima/ima_main.c
+++ b/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);