Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932188AbcLGHJB (ORCPT ); Wed, 7 Dec 2016 02:09:01 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58164 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932150AbcLGHI6 (ORCPT ); Wed, 7 Dec 2016 02:08:58 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Quentin Casasnovas , Miklos Szeredi Subject: [PATCH 4.8 11/35] ovl: fix d_real() for stacked fs Date: Wed, 7 Dec 2016 08:08:27 +0100 Message-Id: <20161207070723.167008314@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161207070722.410336250@linuxfoundation.org> References: <20161207070722.410336250@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1952 Lines: 63 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miklos Szeredi commit c4fcfc1619ea43a8a89ad2f83ff23905eee088bd upstream. Handling of recursion in d_real() is completely broken. Recursion is only done in the 'inode != NULL' case. But when opening the file we have 'inode == NULL' hence d_real() will return an overlay dentry. This won't work since overlayfs doesn't define its own file operations, so all file ops will fail. Fix by doing the recursion first and the check against the inode second. Bash script to reproduce the issue written by Quentin: - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - tmpdir=$(mktemp -d) pushd ${tmpdir} mkdir -p {upper,lower,work} echo -n 'rocks' > lower/ksplice mount -t overlay level_zero upper -o lowerdir=lower,upperdir=upper,workdir=work cat upper/ksplice tmpdir2=$(mktemp -d) pushd ${tmpdir2} mkdir -p {upper,work} mount -t overlay level_one upper -o lowerdir=${tmpdir}/upper,upperdir=upper,workdir=work ls -l upper/ksplice cat upper/ksplice - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - Reported-by: Quentin Casasnovas Signed-off-by: Miklos Szeredi Fixes: 2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()") Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/super.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -329,11 +329,11 @@ static struct dentry *ovl_d_real(struct if (!real) goto bug; + /* Handle recursion */ + real = d_real(real, inode, open_flags); + if (!inode || inode == d_inode(real)) return real; - - /* Handle recursion */ - return d_real(real, inode, open_flags); bug: WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry, inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);