From ec86bfec23e3e5d92ac5e6242f074c92f127d6ef Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Wed, 6 Apr 2016 07:05:41 +1000 Subject: [PATCH] xfs: disallow rw remount on fs with unknown ro-compat features 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(+) diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index 36bd8825bfb0..ef64a1e1a66a 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -1233,6 +1233,16 @@ 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; /* -- 2.34.1