From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7307DC433ED for ; Tue, 6 Apr 2021 13:13:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B421613C6 for ; Tue, 6 Apr 2021 13:13:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242418AbhDFNN2 (ORCPT ); Tue, 6 Apr 2021 09:13:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230527AbhDFNNZ (ORCPT ); Tue, 6 Apr 2021 09:13:25 -0400 Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E80E6C06175F; Tue, 6 Apr 2021 06:13:17 -0700 (PDT) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1lTlW5-00373l-QV; Tue, 06 Apr 2021 13:13:13 +0000 Date: Tue, 6 Apr 2021 13:13:13 +0000 From: Al Viro To: Christian Brauner Cc: Jens Axboe , syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, io-uring@vger.kernel.org Subject: Re: [syzbot] WARNING in mntput_no_expire (2) Message-ID: References: <20210405114437.hjcojekyp5zt6huu@wittgenstein> <20210405170801.zrdhnon6g4ggb6c7@wittgenstein> <20210405200737.qurhkqitoxweousx@wittgenstein> <20210406123505.auxqtquoys6xg6yf@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210406123505.auxqtquoys6xg6yf@wittgenstein> Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Tue, Apr 06, 2021 at 02:35:05PM +0200, Christian Brauner wrote: > And while we're at it might I bring up the possibility of an additional > cleanup of how we currently call path_init(). > Right now we pass the return value from path_init() directly into e.g. > link_path_walk() which as a first thing checks for error. Which feels > rather wrong and has always confused me when looking at these codepaths. Why? > I get that it might make sense for reasons unrelated to path_init() that > link_path_walk() checks its first argument for error but path_init() > should be checked for error right away especially now that we return > early when LOOKUP_CACHED is set without LOOKUP_RCU. But you are making the _callers_ of path_init() do that, for no good reason. > thing especially in longer functions such as path_lookupat() where it > gets convoluted pretty quickly. I think it would be cleaner to have > something like [1]. The early exists make the code easier to reason > about imho. But I get that that's a style discussion. Your variant is a lot more brittle, actually. > @@ -2424,33 +2424,49 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path > int err; > > s = path_init(nd, flags); > - if (IS_ERR(s)) > - return PTR_ERR(s); Where has that come from, BTW? Currently path_lookupat() does no such thing.