From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from imap1.codethink.co.uk ([176.9.8.82]:53132 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751616AbeFHNRx (ORCPT ); Fri, 8 Jun 2018 09:17:53 -0400 Message-ID: <1528463869.2289.92.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 017/268] do d_instantiate/unlock_new_inode combinations safely From: Ben Hutchings To: Al Viro Cc: stable@vger.kernel.org, Mike Marshall , Andreas Dilger , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Date: Fri, 08 Jun 2018 14:17:49 +0100 In-Reply-To: <20180528100203.994843437@linuxfoundation.org> References: <20180528100202.045206534@linuxfoundation.org> <20180528100203.994843437@linuxfoundation.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: On Mon, 2018-05-28 at 11:59 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch.  If anyone has any objections, please let me know. > > ------------------ > > From: Al Viro > > commit 1e2e547a93a00ebc21582c06ca3c6cfea2a309ee upstream. > > For anything NFS-exported we do _not_ want to unlock new inode > before it has grown an alias; original set of fixes got the > ordering right, but missed the nasty complication in case of > lockdep being enabled - unlock_new_inode() does > lockdep_annotate_inode_mutex_key(inode) > which can only be done before anyone gets a chance to touch > ->i_mutex.  Unfortunately, flipping the order and doing > unlock_new_inode() before d_instantiate() opens a window when > mkdir can race with open-by-fhandle on a guessed fhandle, leading > to multiple aliases for a directory inode and all the breakage > that follows from that. > > Correct solution: a new primitive (d_instantiate_new()) > combining these two in the right order - lockdep annotate, then > d_instantiate(), then the rest of unlock_new_inode().  All > combinations of d_instantiate() with unlock_new_inode() should > be converted to that. [...] I think you missed xfs, which has a wrapper around unlock_new_inode() called xfs_finish_inode_setup(). It looks like xfs_generic_create() and xfs_vn_symlink() still need this conversion. Ben. -- Ben Hutchings, Software Developer   Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom