1 files changed, 168 insertions, 42 deletions

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 179589be063a..7a8db78a91d2 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -185,7 +185,7 @@ static int create_dir(struct config_item * k, struct dentry * p,
 	error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
 	if (!error)
 		error = configfs_make_dirent(p->d_fsdata, d, k, mode,
-					     CONFIGFS_DIR);
+					     CONFIGFS_DIR | CONFIGFS_USET_CREATING);
 	if (!error) {
 		error = configfs_create(d, mode, init_dir);
 		if (!error) {
@@ -209,6 +209,9 @@ static int create_dir(struct config_item * k, struct dentry * p,
  *	configfs_create_dir - create a directory for an config_item.
  *	@item:		config_itemwe're creating directory for.
  *	@dentry:	config_item's dentry.
+ *
+ *	Note: user-created entries won't be allowed under this new directory
+ *	until it is validated by configfs_dir_set_ready()
  */
 
 static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
@@ -231,6 +234,44 @@ static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
 	return error;
 }
 
+/*
+ * Allow userspace to create new entries under a new directory created with
+ * configfs_create_dir(), and under all of its chidlren directories recursively.
+ * @sd		configfs_dirent of the new directory to validate
+ *
+ * Caller must hold configfs_dirent_lock.
+ */
+static void configfs_dir_set_ready(struct configfs_dirent *sd)
+{
+	struct configfs_dirent *child_sd;
+
+	sd->s_type &= ~CONFIGFS_USET_CREATING;
+	list_for_each_entry(child_sd, &sd->s_children, s_sibling)
+		if (child_sd->s_type & CONFIGFS_USET_CREATING)
+			configfs_dir_set_ready(child_sd);
+}
+
+/*
+ * Check that a directory does not belong to a directory hierarchy being
+ * attached and not validated yet.
+ * @sd		configfs_dirent of the directory to check
+ *
+ * @return	non-zero iff the directory was validated
+ *
+ * Note: takes configfs_dirent_lock, so the result may change from false to true
+ * in two consecutive calls, but never from true to false.
+ */
+int configfs_dirent_is_ready(struct configfs_dirent *sd)
+{
+	int ret;
+
+	spin_lock(&configfs_dirent_lock);
+	ret = !(sd->s_type & CONFIGFS_USET_CREATING);
+	spin_unlock(&configfs_dirent_lock);
+
+	return ret;
+}
+
 int configfs_create_link(struct configfs_symlink *sl,
 			 struct dentry *parent,
 			 struct dentry *dentry)
@@ -283,6 +324,8 @@ static void remove_dir(struct dentry * d)
  * The only thing special about this is that we remove any files in
  * the directory before we remove the directory, and we've inlined
  * what used to be configfs_rmdir() below, instead of calling separately.
+ *
+ * Caller holds the mutex of the item's inode
  */
 
 static void configfs_remove_dir(struct config_item * item)
@@ -330,7 +373,19 @@ static struct dentry * configfs_lookup(struct inode *dir,
 	struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 	struct configfs_dirent * sd;
 	int found = 0;
-	int err = 0;
+	int err;
+
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 *
+	 * This forbids userspace to read/write attributes of items which may
+	 * not complete their initialization, since the dentries of the
+	 * attributes won't be instantiated.
+	 */
+	err = -ENOENT;
+	if (!configfs_dirent_is_ready(parent_sd))
+		goto out;
 
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_type & CONFIGFS_NOT_PINNED) {
@@ -353,6 +408,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
 		return simple_lookup(dir, dentry, nd);
 	}
 
+out:
 	return ERR_PTR(err);
 }
 
@@ -370,13 +426,17 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex
 	struct configfs_dirent *sd;
 	int ret;
 
+	/* Mark that we're trying to drop the group */
+	parent_sd->s_type |= CONFIGFS_USET_DROPPING;
+
 	ret = -EBUSY;
 	if (!list_empty(&parent_sd->s_links))
 		goto out;
 
 	ret = 0;
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (sd->s_type & CONFIGFS_NOT_PINNED)
+		if (!sd->s_element ||
+		    (sd->s_type & CONFIGFS_NOT_PINNED))
 			continue;
 		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
 			/* Abort if racing with mkdir() */
@@ -385,8 +445,6 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex
 					*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
 				return -EAGAIN;
 			}
-			/* Mark that we're trying to drop the group */
-			sd->s_type |= CONFIGFS_USET_DROPPING;
 
 			/*
 			 * Yup, recursive.  If there's a problem, blame
@@ -414,12 +472,11 @@ static void configfs_detach_rollback(struct dentry *dentry)
 	struct configfs_dirent *parent_sd = dentry->d_fsdata;
 	struct configfs_dirent *sd;
 
-	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
+	parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
+
+	list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
+		if (sd->s_type & CONFIGFS_USET_DEFAULT)
 			configfs_detach_rollback(sd->s_dentry);
-			sd->s_type &= ~CONFIGFS_USET_DROPPING;
-		}
-	}
 }
 
 static void detach_attrs(struct config_item * item)
@@ -558,36 +615,21 @@ static int create_default_group(struct config_group *parent_group,
 static int populate_groups(struct config_group *group)
 {
 	struct config_group *new_group;
-	struct dentry *dentry = group->cg_item.ci_dentry;
 	int ret = 0;
 	int i;
 
 	if (group->default_groups) {
-		/*
-		 * FYI, we're faking mkdir here
-		 * I'm not sure we need this semaphore, as we're called
-		 * from our parent's mkdir.  That holds our parent's
-		 * i_mutex, so afaik lookup cannot continue through our
-		 * parent to find us, let alone mess with our tree.
-		 * That said, taking our i_mutex is closer to mkdir
-		 * emulation, and shouldn't hurt.
-		 */
-		mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
-
 		for (i = 0; group->default_groups[i]; i++) {
 			new_group = group->default_groups[i];
 
 			ret = create_default_group(group, new_group);
-			if (ret)
+			if (ret) {
+				detach_groups(group);
 				break;
+			}
 		}
-
-		mutex_unlock(&dentry->d_inode->i_mutex);
 	}
 
-	if (ret)
-		detach_groups(group);
-
 	return ret;
 }
 
@@ -702,7 +744,15 @@ static int configfs_attach_item(struct config_item *parent_item,
 	if (!ret) {
 		ret = populate_attrs(item);
 		if (ret) {
+			/*
+			 * We are going to remove an inode and its dentry but
+			 * the VFS may already have hit and used them. Thus,
+			 * we must lock them as rmdir() would.
+			 */
+			mutex_lock(&dentry->d_inode->i_mutex);
 			configfs_remove_dir(item);
+			dentry->d_inode->i_flags |= S_DEAD;
+			mutex_unlock(&dentry->d_inode->i_mutex);
 			d_delete(dentry);
 		}
 	}
@@ -710,6 +760,7 @@ static int configfs_attach_item(struct config_item *parent_item,
 	return ret;
 }
 
+/* Caller holds the mutex of the item's inode */
 static void configfs_detach_item(struct config_item *item)
 {
 	detach_attrs(item);
@@ -728,16 +779,30 @@ static int configfs_attach_group(struct config_item *parent_item,
 		sd = dentry->d_fsdata;
 		sd->s_type |= CONFIGFS_USET_DIR;
 
+		/*
+		 * FYI, we're faking mkdir in populate_groups()
+		 * We must lock the group's inode to avoid races with the VFS
+		 * which can already hit the inode and try to add/remove entries
+		 * under it.
+		 *
+		 * We must also lock the inode to remove it safely in case of
+		 * error, as rmdir() would.
+		 */
+		mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
 		ret = populate_groups(to_config_group(item));
 		if (ret) {
 			configfs_detach_item(item);
-			d_delete(dentry);
+			dentry->d_inode->i_flags |= S_DEAD;
 		}
+		mutex_unlock(&dentry->d_inode->i_mutex);
+		if (ret)
+			d_delete(dentry);
 	}
 
 	return ret;
 }
 
+/* Caller holds the mutex of the group's inode */
 static void configfs_detach_group(struct config_item *item)
 {
 	detach_groups(to_config_group(item));
@@ -1035,7 +1100,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	struct configfs_subsystem *subsys;
 	struct configfs_dirent *sd;
 	struct config_item_type *type;
-	struct module *owner = NULL;
+	struct module *subsys_owner = NULL, *new_item_owner = NULL;
 	char *name;
 
 	if (dentry->d_parent == configfs_sb->s_root) {
@@ -1044,6 +1109,16 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	}
 
 	sd = dentry->d_parent->d_fsdata;
+
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 */
+	if (!configfs_dirent_is_ready(sd)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
 	if (!(sd->s_type & CONFIGFS_USET_DIR)) {
 		ret = -EPERM;
 		goto out;
@@ -1062,10 +1137,25 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 		goto out_put;
 	}
 
+	/*
+	 * The subsystem may belong to a different module than the item
+	 * being created.  We don't want to safely pin the new item but
+	 * fail to pin the subsystem it sits under.
+	 */
+	if (!subsys->su_group.cg_item.ci_type) {
+		ret = -EINVAL;
+		goto out_put;
+	}
+	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+	if (!try_module_get(subsys_owner)) {
+		ret = -EINVAL;
+		goto out_put;
+	}
+
 	name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
 	if (!name) {
 		ret = -ENOMEM;
-		goto out_put;
+		goto out_subsys_put;
 	}
 
 	snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
@@ -1094,10 +1184,10 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	kfree(name);
 	if (ret) {
 		/*
-		 * If item == NULL, then link_obj() was never called.
+		 * If ret != 0, then link_obj() was never called.
 		 * There are no extra references to clean up.
 		 */
-		goto out_put;
+		goto out_subsys_put;
 	}
 
 	/*
@@ -1111,8 +1201,8 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 		goto out_unlink;
 	}
 
-	owner = type->ct_owner;
-	if (!try_module_get(owner)) {
+	new_item_owner = type->ct_owner;
+	if (!try_module_get(new_item_owner)) {
 		ret = -EINVAL;
 		goto out_unlink;
 	}
@@ -1142,6 +1232,8 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 
 	spin_lock(&configfs_dirent_lock);
 	sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
+	if (!ret)
+		configfs_dir_set_ready(dentry->d_fsdata);
 	spin_unlock(&configfs_dirent_lock);
 
 out_unlink:
@@ -1159,9 +1251,13 @@ out_unlink:
 		mutex_unlock(&subsys->su_mutex);
 
 		if (module_got)
-			module_put(owner);
+			module_put(new_item_owner);
 	}
 
+out_subsys_put:
+	if (ret)
+		module_put(subsys_owner);
+
 out_put:
 	/*
 	 * link_obj()/link_group() took a reference from child->parent,
@@ -1180,7 +1276,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	struct config_item *item;
 	struct configfs_subsystem *subsys;
 	struct configfs_dirent *sd;
-	struct module *owner = NULL;
+	struct module *subsys_owner = NULL, *dead_item_owner = NULL;
 	int ret;
 
 	if (dentry->d_parent == configfs_sb->s_root)
@@ -1207,6 +1303,15 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		return -EINVAL;
 	}
 
+	/* configfs_mkdir() shouldn't have allowed this */
+	BUG_ON(!subsys->su_group.cg_item.ci_type);
+	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+
+	/*
+	 * Ensure that no racing symlink() will make detach_prep() fail while
+	 * the new link is temporarily attached
+	 */
+	mutex_lock(&configfs_symlink_mutex);
 	spin_lock(&configfs_dirent_lock);
 	do {
 		struct mutex *wait_mutex;
@@ -1215,6 +1320,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		if (ret) {
 			configfs_detach_rollback(dentry);
 			spin_unlock(&configfs_dirent_lock);
+			mutex_unlock(&configfs_symlink_mutex);
 			if (ret != -EAGAIN) {
 				config_item_put(parent_item);
 				return ret;
@@ -1224,10 +1330,12 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 			mutex_lock(wait_mutex);
 			mutex_unlock(wait_mutex);
 
+			mutex_lock(&configfs_symlink_mutex);
 			spin_lock(&configfs_dirent_lock);
 		}
 	} while (ret == -EAGAIN);
 	spin_unlock(&configfs_dirent_lock);
+	mutex_unlock(&configfs_symlink_mutex);
 
 	/* Get a working ref for the duration of this function */
 	item = configfs_get_config_item(dentry);
@@ -1236,7 +1344,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	config_item_put(parent_item);
 
 	if (item->ci_type)
-		owner = item->ci_type->ct_owner;
+		dead_item_owner = item->ci_type->ct_owner;
 
 	if (sd->s_type & CONFIGFS_USET_DIR) {
 		configfs_detach_group(item);
@@ -1258,7 +1366,8 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	/* Drop our reference from above */
 	config_item_put(item);
 
-	module_put(owner);
+	module_put(dead_item_owner);
+	module_put(subsys_owner);
 
 	return 0;
 }
@@ -1314,13 +1423,24 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
 {
 	struct dentry * dentry = file->f_path.dentry;
 	struct configfs_dirent * parent_sd = dentry->d_fsdata;
+	int err;
 
 	mutex_lock(&dentry->d_inode->i_mutex);
-	file->private_data = configfs_new_dirent(parent_sd, NULL);
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 */
+	err = -ENOENT;
+	if (configfs_dirent_is_ready(parent_sd)) {
+		file->private_data = configfs_new_dirent(parent_sd, NULL);
+		if (IS_ERR(file->private_data))
+			err = PTR_ERR(file->private_data);
+		else
+			err = 0;
+	}
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
-	return IS_ERR(file->private_data) ? PTR_ERR(file->private_data) : 0;
-
+	return err;
 }
 
 static int configfs_dir_close(struct inode *inode, struct file *file)
@@ -1491,6 +1611,10 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 		if (err) {
 			d_delete(dentry);
 			dput(dentry);
+		} else {
+			spin_lock(&configfs_dirent_lock);
+			configfs_dir_set_ready(dentry->d_fsdata);
+			spin_unlock(&configfs_dirent_lock);
 		}
 	}
 
@@ -1517,11 +1641,13 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 	mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
 			  I_MUTEX_PARENT);
 	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+	mutex_lock(&configfs_symlink_mutex);
 	spin_lock(&configfs_dirent_lock);
 	if (configfs_detach_prep(dentry, NULL)) {
 		printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
 	}
 	spin_unlock(&configfs_dirent_lock);
+	mutex_unlock(&configfs_symlink_mutex);
 	configfs_detach_group(&group->cg_item);
 	dentry->d_inode->i_flags |= S_DEAD;
 	mutex_unlock(&dentry->d_inode->i_mutex);