On Tue, 2017-07-25 at 14:43 -0500, Serge E. Hallyn wrote:

...

quoted

+static void free_ns_status_cache(struct ima_namespace *ns)
+{
+	struct ns_status *status, *next;
+
+	write_lock(&ns->ns_status_lock);
+	rbtree_postorder_for_each_entry_safe(status, next,
+					     &ns->ns_status_tree, rb_node)
+		kmem_cache_free(ns->ns_status_cache, status);
+	ns->ns_status_tree = RB_ROOT;
+	write_unlock(&ns->ns_status_lock);
+	kmem_cache_destroy(ns->ns_status_cache);
+}
+
 static void destroy_ima_ns(struct ima_namespace *ns)
 {
 	put_user_ns(ns->user_ns);
 	ns_free_inum(&ns->ns);
+	free_ns_status_cache(ns);
 	kfree(ns);
 }
 

@@ -181,3 +198,106 @@ struct ima_namespace init_ima_ns = {
 	.parent = NULL,
 };
 EXPORT_SYMBOL(init_ima_ns);
+
+/*
+ * __ima_ns_status_find - return the ns_status associated with an inode
+ */
+static struct ns_status *__ima_ns_status_find(struct ima_namespace *ns,
+					      struct inode *inode)
+{
+	struct ns_status *status;
+	struct rb_node *n = ns->ns_status_tree.rb_node;
+
+	while (n) {
+		status = rb_entry(n, struct ns_status, rb_node);
+
+		if (inode < status->inode)
+			n = n->rb_left;
+		else if (inode->i_ino > status->i_ino)
+			n = n->rb_right;
+		else
+			break;
+	}
+	if (!n)
+		return NULL;
+
+	return status;
+}
+
+/*
+ * ima_ns_status_find - return the ns_status associated with an inode
+ */
+static struct ns_status *ima_ns_status_find(struct ima_namespace *ns,
+					    struct inode *inode)
+{
+	struct ns_status *status;
+
+	read_lock(&ns->ns_status_lock);
+	status = __ima_ns_status_find(ns, inode);
+	read_unlock(&ns->ns_status_lock);
+
+	return status;
+}

...

quoted

+
+struct ns_status *ima_get_ns_status(struct ima_namespace *ns,
+				    struct inode *inode)
+{
+	struct ns_status *status;
+	int skip_insert = 0;
+
+	status = ima_ns_status_find(ns, inode);
+	if (status) {
+		/*
+		 * Unlike integrity_iint_cache we are not free'ing the
+		 * ns_status data when the inode is free'd. So, in addition to
+		 * checking the inode pointer, we need to make sure the
+		 * (i_generation, i_ino) pair matches as well. In the future
+		 * we might want to add support for lazily walking the rbtree
+		 * to clean it up.
+		 */
+		if (inode->i_ino == status->i_ino &&
+		    inode->i_generation == status->i_generation)
+			return status;
+
+		/* Same inode number is reused, overwrite the ns_status */
+		skip_insert = 1;
+	} else {
+		status = kmem_cache_alloc(ns->ns_status_cache, GFP_NOFS);
+		if (!status)
+			return ERR_PTR(-ENOMEM);
+	}

What prevents the status from being freed between the read_lock
in ima_ns_status_find() and the write_lock in the following line?

IIUC it's that ns is always current's ima_ns, which will pin the ns
and cause no statuses to be freed.  But then the ns should probably
not be passed in here?  Or a comment should say that ns must be
pinned?

Just trying to make sure I understand the locking.

iint's are only freed after the last reference to the inode is deleted
in __fput(). ?Refer to ima_file_free(). ?ns_status is a bit different
in that they are freed on namespace cleanup.

Mimi

quoted

+	write_lock(&ns->ns_status_lock);
+
+	if (!skip_insert)
+		insert_ns_status(ns, inode, status);
+
+	status->inode = inode;
+	status->i_ino = inode->i_ino;
+	status->i_generation = inode->i_generation;
+	status->flags = 0UL;
+	write_unlock(&ns->ns_status_lock);
+
+	return status;
+}
-- 
2.9.

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