On Thu, Sep 10, 2020 at 11:27:06AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> The V4 filesystem format contains known weaknesses in the on-disk format
> that make metadata verification diffiult. In addition, the format will
> does not support dates past 2038 and will not be upgraded to do so.
> Therefore, we should start the process of retiring the old format to
> close off attack surfaces and to encourage users to migrate onto V5.
>
> Therefore, make XFS V4 support a configurable option. For the first
> period it will be default Y in case some distributors want to withdraw
> support early; for the second period it will be default N so that anyone
> who wishes to continue support can do so; and after that, support will
> be removed from the kernel.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/Kconfig | 18 ++++++++++++++++++
> fs/xfs/xfs_mount.c | 11 +++++++++++
> 2 files changed, 29 insertions(+)
>
> diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
> index e685299eb3d2..db54ca9914c7 100644
> --- a/fs/xfs/Kconfig
> +++ b/fs/xfs/Kconfig
> @@ -22,6 +22,24 @@ config XFS_FS
> system of your root partition is compiled as a module, you'll need
> to use an initial ramdisk (initrd) to boot.
>
> +config XFS_SUPPORT_V4
> + bool "Support deprecated V4 format"
> + default y
> + help
> + The V4 filesystem format lacks certain features that are supported
> + by the V5 format, such as metadata checksumming, strengthened
> + metadata verification, and the ability to store timestamps past the
> + year 2038. Because of this, the V4 format is deprecated. All users
> + should upgrade by backing up their files, reformatting, and restoring
> + from the backup.
> +
> + This option will become default N in September 2025. Support for the
> + V4 format will be removed entirely in September 2030. Distributors
> + can say N here to withdraw support earlier.
> +
> + To continue supporting the old V4 format, say Y.
> + To close off an attack surface, say N.
> +
> config XFS_QUOTA
> bool "XFS Quota support"
> depends on XFS_FS
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index ed69c4bfda71..48c0175b9457 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -315,6 +315,17 @@ xfs_readsb(
> goto release_buf;
> }
>
> +#ifndef CONFIG_XFS_SUPPORT_V4
> + /* V4 support is undergoing deprecation. */
> + if (!xfs_sb_version_hascrc(sbp)) {
> + if (loud)
> + xfs_warn(mp,
> + "Deprecated V4 format not supported by kernel.");
> + error = -EINVAL;
> + goto release_buf;
> + }
> +#endif
Fine by me.
You forgot to add the V4 format to the deprecation schedule in
Documentation/filesystems/.....
<nggggh>
(where TF has this bit of XFS documentation been moved to???)
in Documentation/admin-guide/xfs.rst.
-Dave.
[ Why did that file get moved rather than just linked from it's
original spot in all the -filesystem- documentation? Can we move it
back, please, like all the other <filesystem>.rst files in
Documentation/filesystems/ ? ]
--
Dave Chinner
david@xxxxxxxxxxxxx
