From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933045AbXBLGqA (ORCPT ); Mon, 12 Feb 2007 01:46:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933048AbXBLGqA (ORCPT ); Mon, 12 Feb 2007 01:46:00 -0500 Received: from out5.smtp.messagingengine.com ([66.111.4.29]:53648 "EHLO out5.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933045AbXBLGp7 (ORCPT ); Mon, 12 Feb 2007 01:45:59 -0500 X-Sasl-enc: crj9XA/onexJFJmLVtHVe9l2bSt/iPYAtLNyWgdU7AaL 1171262756 Subject: Re: [PATCH 2/2] Re: [autofs] Bad race condition in the new autofs protocol somewhere From: Ian Kent To: Olivier Galibert Cc: "Hack inc." , autofs@linux.kernel.org In-Reply-To: <1171262594.18376.13.camel@raven.themaw.net> References: <20070207173414.GA64492@dspnet.fr.eu.org> <1170871661.3415.36.camel@raven.themaw.net> <20070207181817.GA75717@dspnet.fr.eu.org> <1170901990.3383.18.camel@raven.themaw.net> <1171262594.18376.13.camel@raven.themaw.net> Content-Type: text/plain Date: Mon, 12 Feb 2007 15:46:40 +0900 Message-Id: <1171262800.18376.16.camel@raven.themaw.net> Mime-Version: 1.0 X-Mailer: Evolution 2.8.0 (2.8.0-32.el5) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2007-02-12 at 15:43 +0900, Ian Kent wrote: > On Thu, 2007-02-08 at 11:33 +0900, Ian Kent wrote: > > On Wed, 2007-02-07 at 19:18 +0100, Olivier Galibert wrote: > > > On Thu, Feb 08, 2007 at 03:07:41AM +0900, Ian Kent wrote: > > > > It may be better to update to a later kernel so I don't have to port the > > > > patch to several different kernels. Is that possible? > > > > > > Sure, 2.6.20 or -git? > > > > 2.6.20 has all the patches I've proposed so far except for the one we're > > working on so that would be best for me. > > > > Seems there may still be a problem with the patch so I'll let you know > > what's happening as soon as I can. > > I think I'm just about done. > > Could you try using the two patches here against 2.6.20 please: > > Ian --- --- linux-2.6.20/fs/autofs4/root.c.lookup-check-unhased 2007-02-12 13:49:46.000000000 +0900 +++ linux-2.6.20/fs/autofs4/root.c 2007-02-12 13:54:58.000000000 +0900 @@ -655,14 +655,29 @@ static struct dentry *autofs4_lookup(str /* * If this dentry is unhashed, then we shouldn't honour this - * lookup even if the dentry is positive. Returning ENOENT here - * doesn't do the right thing for all system calls, but it should - * be OK for the operations we permit from an autofs. + * lookup. Returning ENOENT here doesn't do the right thing + * for all system calls, but it should be OK for the operations + * we permit from an autofs. */ if (dentry->d_inode && d_unhashed(dentry)) { + /* + * A user space application can (and has done in the past) + * remove and re-create this directory during the callback. + * This can leave us with an unhashed dentry, but a + * successful mount! So we need to perform another + * cached lookup in case the dentry now exists. + */ + struct dentry *parent = dentry->d_parent; + struct dentry *new = d_lookup(parent, &dentry->d_name); + if (new != NULL) + dentry = new; + else + dentry = ERR_PTR(-ENOENT); + if (unhashed) dput(unhashed); - return ERR_PTR(-ENOENT); + + return dentry; } if (unhashed)