ecryptfs_rename(): verify that lower dentries are still OK after lock_rename()

We get lower layer dentries, find their parents, do lock_rename() and
proceed to vfs_rename().  However, we do not check that dentries still
have the same parents and are not unlinked.  Need to check that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ecryptfs/inode.c

@@ -593,11 +593,16 @@ ecryptfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	lower_new_dir_dentry = dget_parent(lower_new_dentry);
 	target_inode = d_inode(new_dentry);
 	trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
+	rc = -EINVAL;
+	if (lower_old_dentry->d_parent != lower_old_dir_dentry)
+		goto out_lock;
+	if (lower_new_dentry->d_parent != lower_new_dir_dentry)
+		goto out_lock;
+	if (d_unhashed(lower_old_dentry) || d_unhashed(lower_new_dentry))
+		goto out_lock;
 	/* source should not be ancestor of target */
-	if (trap == lower_old_dentry) {
-		rc = -EINVAL;
+	if (trap == lower_old_dentry)
 		goto out_lock;
-	}
 	/* target should not be ancestor of source */
 	if (trap == lower_new_dentry) {
 		rc = -ENOTEMPTY;