ksmbd: move leading slash check to smb2_get_name()

If the directory name in the root of the share starts with
character like 镜(0x955c) or Ṝ(0x1e5c), it (and anything inside)
cannot be accessed. The leading slash check must be checked after
converting unicode to nls string.

Cc: [e-mail]
Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/server/smb2pdu.c

···
 		return name;
 	}
 
+	if (*name == '\\') {
+		pr_err("not allow directory name included leading slash\n");
+		kfree(name);
+		return ERR_PTR(-EINVAL);
+	}
+
 	ksmbd_conv_path_to_unix(name);
 	ksmbd_strip_last_slash(name);
 	return name;
···
 	}
 
 	if (req->NameLength) {
-		if ((req->CreateOptions & FILE_DIRECTORY_FILE_LE) &&
-		    *(char *)req->Buffer == '\\') {
-			pr_err("not allow directory name included leading slash\n");
-			rc = -EINVAL;
-			goto err_out2;
-		}
-
 		name = smb2_get_name((char *)req + le16_to_cpu(req->NameOffset),
 				     le16_to_cpu(req->NameLength),
 				     work->conn->local_nls);
 		if (IS_ERR(name)) {
 			rc = PTR_ERR(name);
-			if (rc != -ENOMEM)
-				rc = -ENOENT;
 			name = NULL;
 			goto err_out2;
 		}