From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43732 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753493AbcFEWDC (ORCPT ); Sun, 5 Jun 2016 18:03:02 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Sandeen , Bill ODonnell , Dave Chinner , Dave Chinner Subject: [PATCH 4.6 114/121] xfs: disallow rw remount on fs with unknown ro-compat features Date: Sun, 5 Jun 2016 14:44:26 -0700 Message-Id: <20160605214421.257319530@linuxfoundation.org> In-Reply-To: <20160605214417.708509043@linuxfoundation.org> References: <20160605214417.708509043@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Sandeen commit d0a58e833931234c44e515b5b8bede32bd4e6eed upstream. Today, a kernel which refuses to mount a filesystem read-write due to unknown ro-compat features can still transition to read-write via the remount path. The old kernel is most likely none the wiser, because it's unaware of the new feature, and isn't using it. However, writing to the filesystem may well corrupt metadata related to that new feature, and moving to a newer kernel which understand the feature will have problems. Right now the only ro-compat feature we have is the free inode btree, which showed up in v3.16. It would be good to push this back to all the active stable kernels, I think, so that if anyone is using newer mkfs (which enables the finobt feature) with older kernel releases, they'll be protected. Signed-off-by: Eric Sandeen Reviewed-by: Bill O'Donnell Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner Signed-off-by: Greg Kroah-Hartman --- fs/xfs/xfs_super.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -1276,6 +1276,16 @@ xfs_fs_remount( return -EINVAL; } + if (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5 && + xfs_sb_has_ro_compat_feature(sbp, + XFS_SB_FEAT_RO_COMPAT_UNKNOWN)) { + xfs_warn(mp, +"ro->rw transition prohibited on unknown (0x%x) ro-compat filesystem", + (sbp->sb_features_ro_compat & + XFS_SB_FEAT_RO_COMPAT_UNKNOWN)); + return -EINVAL; + } + mp->m_flags &= ~XFS_MOUNT_RDONLY; /*