ima: allocating iint improvements
Dmitry Kasatkin [Wed, 19 Oct 2011 09:04:40 +0000 (12:04 +0300)]
With IMA-appraisal's removal of the iint mutex and taking the i_mutex
instead, allocating the iint becomes a lot simplier, as we don't need
to be concerned with two processes racing to allocate the iint. This
patch cleans up and improves performance for allocating the iint.

- removed redundant double i_mutex locking
- combined iint allocation with tree search

Changelog v2:
- removed the rwlock/read_lock changes from this patch

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>

include/linux/integrity.h
security/integrity/iint.c
security/integrity/ima/ima_main.c

index a0c4125..66c5fe9 100644 (file)
@@ -22,13 +22,14 @@ enum integrity_status {
 
 /* List of EVM protected security xattrs */
 #ifdef CONFIG_INTEGRITY
-extern int integrity_inode_alloc(struct inode *inode);
+extern struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
 extern void integrity_inode_free(struct inode *inode);
 
 #else
-static inline int integrity_inode_alloc(struct inode *inode)
+static inline struct integrity_iint_cache *
+                               integrity_inode_get(struct inode *inode)
 {
-       return 0;
+       return NULL;
 }
 
 static inline void integrity_inode_free(struct inode *inode)
index e600986..c91a436 100644 (file)
@@ -80,24 +80,26 @@ static void iint_free(struct integrity_iint_cache *iint)
 }
 
 /**
- * integrity_inode_alloc - allocate an iint associated with an inode
+ * integrity_inode_get - find or allocate an iint associated with an inode
  * @inode: pointer to the inode
+ * @return: allocated iint
+ *
+ * Caller must lock i_mutex
  */
-int integrity_inode_alloc(struct inode *inode)
+struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
 {
        struct rb_node **p;
-       struct rb_node *new_node, *parent = NULL;
-       struct integrity_iint_cache *new_iint, *test_iint;
-       int rc;
+       struct rb_node *node, *parent = NULL;
+       struct integrity_iint_cache *iint, *test_iint;
 
-       new_iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
-       if (!new_iint)
-               return -ENOMEM;
+       iint = integrity_iint_find(inode);
+       if (iint)
+               return iint;
 
-       new_iint->inode = inode;
-       new_node = &new_iint->rb_node;
+       iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
+       if (!iint)
+               return NULL;
 
-       mutex_lock(&inode->i_mutex);    /* i_flags */
        spin_lock(&integrity_iint_lock);
 
        p = &integrity_iint_tree.rb_node;
@@ -105,29 +107,20 @@ int integrity_inode_alloc(struct inode *inode)
                parent = *p;
                test_iint = rb_entry(parent, struct integrity_iint_cache,
                                     rb_node);
-               rc = -EEXIST;
                if (inode < test_iint->inode)
                        p = &(*p)->rb_left;
-               else if (inode > test_iint->inode)
-                       p = &(*p)->rb_right;
                else
-                       goto out_err;
+                       p = &(*p)->rb_right;
        }
 
+       iint->inode = inode;
+       node = &iint->rb_node;
        inode->i_flags |= S_IMA;
-       rb_link_node(new_node, parent, p);
-       rb_insert_color(new_node, &integrity_iint_tree);
+       rb_link_node(node, parent, p);
+       rb_insert_color(node, &integrity_iint_tree);
 
        spin_unlock(&integrity_iint_lock);
-       mutex_unlock(&inode->i_mutex);  /* i_flags */
-
-       return 0;
-out_err:
-       spin_unlock(&integrity_iint_lock);
-       mutex_unlock(&inode->i_mutex);  /* i_flags */
-       iint_free(new_iint);
-
-       return rc;
+       return iint;
 }
 
 /**
index 6eb28d4..df65212 100644 (file)
@@ -162,19 +162,14 @@ static int process_measurement(struct file *file, const unsigned char *filename,
        if (!action)
                return 0;
 
-retry:
-       iint = integrity_iint_find(inode);
-       if (!iint) {
-               rc = integrity_inode_alloc(inode);
-               if (!rc || rc == -EEXIST)
-                       goto retry;
-               return rc;
-       }
-
        must_appraise = action & IMA_APPRAISE;
 
        mutex_lock(&inode->i_mutex);
 
+       iint = integrity_inode_get(inode);
+       if (!iint)
+               goto out;
+
        /* Determine if already appraised/measured based on bitmask
         * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED) */
        iint->flags |= action;