ovl: detect overlapping layers

[linux-2.6-microblaze.git] / fs / overlayfs / inode.c

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b48273e..f7eba21 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -777,6 +777,54 @@ struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
        return inode;
 }
 
+bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+       struct inode *key = d_inode(dir);
+       struct inode *trap;
+       bool res;
+
+       trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
+       if (!trap)
+               return false;
+
+       res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
+                                 !ovl_inode_lower(trap);
+
+       iput(trap);
+       return res;
+}
+
+/*
+ * Create an inode cache entry for layer root dir, that will intentionally
+ * fail ovl_verify_inode(), so any lookup that will find some layer root
+ * will fail.
+ */
+struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+       struct inode *key = d_inode(dir);
+       struct inode *trap;
+
+       if (!d_is_dir(dir))
+               return ERR_PTR(-ENOTDIR);
+
+       trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
+                           ovl_inode_set, key);
+       if (!trap)
+               return ERR_PTR(-ENOMEM);
+
+       if (!(trap->i_state & I_NEW)) {
+               /* Conflicting layer roots? */
+               iput(trap);
+               return ERR_PTR(-ELOOP);
+       }
+
+       trap->i_mode = S_IFDIR;
+       trap->i_flags = S_DEAD;
+       unlock_new_inode(trap);
+
+       return trap;
+}
+
 /*
  * Does overlay inode need to be hashed by lower inode?
  */