ima: allocating iint improvements

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>

3 files changed, 27 insertions, 38 deletions

diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index a0c41256cb92..66c5fe9550a5 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -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)
diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index e600986aa49f..c91a436e13ac 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -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;
 }
 
 /**
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 6eb28d47e74b..df6521296051 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -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;