Commit d0a58e83 authored Apr 06, 2016 by Eric Sandeen Committed by Dave Chinner Apr 06, 2016

xfs: disallow rw remount on fs with unknown ro-compat features



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.

Cc: <stable@vger.kernel.org> # 3.10.x-
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

parent f55532a0

fs/xfs/xfs_super.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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;

		/*

Admin message