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

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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>
This commit is contained in:
Eric Sandeen 2016-04-06 07:05:41 +10:00 committed by Dave Chinner
parent f55532a0c0
commit d0a58e8339
1 changed files with 10 additions and 0 deletions
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10
fs/xfs/xfs_super.c
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@ -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;
/*