1 files changed, 26 insertions, 0 deletions

diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index 0004d18c40ac..bf74973b0492 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -31,6 +31,9 @@
 #include <linux/configfs.h>
 #include "configfs_internal.h"
 
+/* Protects attachments of new symlinks */
+DEFINE_MUTEX(configfs_symlink_mutex);
+
 static int item_depth(struct config_item * item)
 {
         struct config_item * p = item;
@@ -73,11 +76,20 @@ static int create_link(struct config_item *parent_item,
         struct configfs_symlink *sl;
         int ret;
 
+        ret = -ENOENT;
+        if (!configfs_dirent_is_ready(target_sd))
+                goto out;
         ret = -ENOMEM;
         sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
         if (sl) {
                 sl->sl_target = config_item_get(item);
                 spin_lock(&configfs_dirent_lock);
+                if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
+                        spin_unlock(&configfs_dirent_lock);
+                        config_item_put(item);
+                        kfree(sl);
+                        return -ENOENT;
+                }
                 list_add(&sl->sl_list, &target_sd->s_links);
                 spin_unlock(&configfs_dirent_lock);
                 ret = configfs_create_link(sl, parent_item->ci_dentry,
@@ -91,6 +103,7 @@ static int create_link(struct config_item *parent_item,
                 }
         }
 
+out:
         return ret;
 }
 
@@ -120,6 +133,7 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
 {
         int ret;
         struct nameidata nd;
+        struct configfs_dirent *sd;
         struct config_item *parent_item;
         struct config_item *target_item;
         struct config_item_type *type;
@@ -128,9 +142,19 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
         if (dentry->d_parent == configfs_sb->s_root)
                 goto out;
 
+        sd = dentry->d_parent->d_fsdata;
+        /*
+         * Fake invisibility if dir belongs to a group/default groups hierarchy
+         * being attached
+         */
+        ret = -ENOENT;
+        if (!configfs_dirent_is_ready(sd))
+                goto out;
+
         parent_item = configfs_get_config_item(dentry->d_parent);
         type = parent_item->ci_type;
 
+        ret = -EPERM;
         if (!type || !type->ct_item_ops ||
             !type->ct_item_ops->allow_link)
                 goto out_put;
@@ -141,7 +165,9 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
 
         ret = type->ct_item_ops->allow_link(parent_item, target_item);
         if (!ret) {
+                mutex_lock(&configfs_symlink_mutex);
                 ret = create_link(parent_item, target_item, dentry);
+                mutex_unlock(&configfs_symlink_mutex);
                 if (ret && type->ct_item_ops->drop_link)
                         type->ct_item_ops->drop_link(parent_item,
                                                      target_item);