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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 8316DC10DCE for ; Fri, 6 Mar 2020 21:28:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 566CD206D7 for ; Fri, 6 Mar 2020 21:28:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726397AbgCFV2f (ORCPT ); Fri, 6 Mar 2020 16:28:35 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:39692 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726162AbgCFV2e (ORCPT ); Fri, 6 Mar 2020 16:28:34 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jAKW7-006Vf9-Km; Fri, 06 Mar 2020 21:28:23 +0000 Date: Fri, 6 Mar 2020 21:28:23 +0000 From: Al Viro To: Miklos Szeredi Cc: Ian Kent , David Howells , Christian Brauner , James Bottomley , Steven Whitehouse , Miklos Szeredi , Christian Brauner , Jann Horn , "Darrick J. Wong" , Linux API , linux-fsdevel , lkml , Greg Kroah-Hartman Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17] Message-ID: <20200306212823.GG23230@ZenIV.linux.org.uk> References: <20200306162549.GA28467@miu.piliscsaba.redhat.com> <20200306194322.GY23230@ZenIV.linux.org.uk> <20200306195823.GZ23230@ZenIV.linux.org.uk> <20200306200522.GA23230@ZenIV.linux.org.uk> <20200306203705.GB23230@ZenIV.linux.org.uk> <20200306203844.GC23230@ZenIV.linux.org.uk> <20200306204523.GD23230@ZenIV.linux.org.uk> <20200306204926.GE23230@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Mar 06, 2020 at 09:51:50PM +0100, Miklos Szeredi wrote: > On Fri, Mar 6, 2020 at 9:49 PM Al Viro wrote: > > > > On Fri, Mar 06, 2020 at 08:45:23PM +0000, Al Viro wrote: > > > On Fri, Mar 06, 2020 at 08:38:44PM +0000, Al Viro wrote: > > > > On Fri, Mar 06, 2020 at 08:37:05PM +0000, Al Viro wrote: > > > > > > > > > You are misreading mntput_no_expire(), BTW - your get_mount() can > > > > > bloody well race with umount(2), hitting the moment when we are done > > > > > figuring out whether it's busy but hadn't cleaned ->mnt_ns (let alone > > > > > set MNT_DOOMED) yet. If somebody calls umount(2) on a filesystem that > > > > > is not mounted anywhere else, they are not supposed to see the sucker > > > > > return 0 until the filesystem is shut down. You break that. > > > > > > > > While we are at it, d_alloc_parallel() requires i_rwsem on parent held > > > > at least shared. > > > > > > Egads... Let me see if I got it right - you are providing procfs symlinks > > > to objects on the internal mount of that thing. And those objects happen > > > to be directories, so one can get to their parent that way. Or am I misreading > > > that thing? > > > > IDGI. You have (in your lookup) kstrtoul, followed by snprintf, followed > > by strcmp and WARN_ON() in case of mismatch? Is there any point in having > > stat(2) on "00" spew into syslog? Confused... > > The WARN_ON() is for the buffer overrun, not for the strcmp mismatch. That makes even less sense - buffer overrun on snprintf of an int into 32-character array? That's what, future-proofing it for the time we manage to issue 10^31 syscalls since the (much closer) moment when we get 128bit int?