From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750998AbVIVVJl (ORCPT ); Thu, 22 Sep 2005 17:09:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751204AbVIVVJl (ORCPT ); Thu, 22 Sep 2005 17:09:41 -0400 Received: from mx1.redhat.com ([66.187.233.31]:36840 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1750998AbVIVVJk (ORCPT ); Thu, 22 Sep 2005 17:09:40 -0400 From: Jeff Moyer MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17203.7543.949262.883138@segfault.boston.redhat.com> Date: Thu, 22 Sep 2005 17:09:11 -0400 To: Ian Kent Cc: autofs@linux.kernel.org, linux-kernel@vger.kernel.org Subject: Re: autofs4 looks up wrong path element when ghosting is enabled In-Reply-To: References: <17200.23724.686149.394150@segfault.boston.redhat.com> X-Mailer: VM 7.17 under 21.4 (patch 15) "Security Through Obscurity" XEmacs Lucid Reply-To: jmoyer@redhat.com X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org ==> Regarding Re: autofs4 looks up wrong path element when ghosting is enabled; Ian Kent adds: raven> On Tue, 20 Sep 2005, Jeff Moyer wrote: >> Hi, Ian, list, >> >> I have a bug filed against autofs when ghosting is enabled. The best way >> to describe the bug is to walk through the reproducer, I guess. >> >> Take the following maps, for example: >> >> auto.master >> /sbox auto.sbox >> >> auto.sbox: >> src segfault:/sbox/src/ >> >> Let's say that there is a file, id3_0.12.orig.tar.gz, in segfault:/sbox/src/. >> >> To reproduce the problem, stop the nfs service on the server. >> >> On the client, do an 'ls /sbox/src/id3_012.orig.tar.gz'. This will fail, >> as well it should. However, if we look in the logs, we find this: >> >> automount[1182]: handle_packet_missing: token 1, name src >> automount[1182]: attempting to mount entry /sbox/src >> ... >> automount[1481]: mount(nfs): calling mkdir_path /sbox/src >> automount[1481]: mount(nfs): calling mount -t nfs -s-o tcp,intr,timeo=600,rsize=8192,wsize=8192,retrans=5 segfault:/sbox/src /sbox/src >> automount[1481]: >> mount: RPC: Program not registered >> automount[1481]: mount(nfs): add_bad_host: segfault:/sbox/src >> automount[1481]: mount(nfs): nfs: mount failure segfault:/sbox/src on /sbox/src >> automount[1481]: failed to mount /sbox/src >> ... >> automount[1182]: send_fail: token=1 >> automount[1182]: handle_packet: type = 0 >> automount[1182]: handle_packet_missing: token 2, name src/id3_0.12.orig.tar.gz >> automount[1182]: attempting to mount entry /sbox/src/id3_0.12.orig.tar.gz >> >> Noteworthy are these last two lines! Even though the mount failed, we are >> continuing the lookup. The culprit is here, in cached_lookup: >> >> if (!dentry->d_op->d_revalidate(dentry, flags) && !d_invalidate(dentry)) { >> dput(dentry); >> dentry = NULL; >> } >> >> d_revalidate points to autofs4_revalidate, which calls try_to_fill_dentry, >> which will return a status of 0. Since ghosting is enabled, >> d_invalidate(dentry) will return -EBUSY, and so we return the dentry to raven> the >> caller, which then continues the lookup. >> >> Ian, I'm not really sure how we can address this issue without VFS >> changes. Any ideas? >> raven> I'm aware of this problem. raven> I'm not sure how to deal with it yet. raven> The case above is probably not that difficult to solve but if the last raven> component is a directory it's hard to work out it's a problem. Ugh. If you're thinking what I think you're thinking, that's an ugly hack. raven> There's more information here than I've gathhered so far. >> Oh, also note that, once the nfs service is started up again on the server, >> the lookup of a specific file name will still fail! In this case, the >> daemon won't even be called. raven> I'll have to check this out. raven> It could be helpful. Well, I've provided a reproducer. If you'd like log output from the kernel side, let me know. I can certainly provide that. -Jeff