On Fri, Oct 21, 2016 at 02:48:41PM +0200, Richard Weinberger wrote:
> Starting with version 5 the following properties change:
>  - UBIFS_FLG_DOUBLE_HASH is mandatory
>  - UBIFS_FLG_ENCRYPTION is optional but depdens on UBIFS_FLG_DOUBLE_HASH
>  - Filesystems with unknown super block flags will be rejected, this
>    allows us in future to add new features without raising the UBIFS
>    write version.
> 
> Signed-off-by: Richard Weinberger <rich...@nod.at>
> ---
>  fs/ubifs/sb.c          | 17 +++++++++++++++++
>  fs/ubifs/ubifs-media.h |  4 +++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
> index 54cef70ea16f..7f1ead29e727 100644
> --- a/fs/ubifs/sb.c
> +++ b/fs/ubifs/sb.c
> @@ -466,6 +466,16 @@ static int validate_sb(struct ubifs_info *c, struct 
> ubifs_sb_node *sup)
>               goto failed;
>       }
>  
> +     if (!c->double_hash && c->fmt_version >= 5) {
> +             err = 16;
> +             goto failed;
> +     }
> +
> +     if (c->encrypted && c->fmt_version < 5) {
> +             err = 17;
> +             goto failed;
> +     }
> +
>       return 0;
>  
>  failed:
> @@ -624,6 +634,13 @@ int ubifs_read_superblock(struct ubifs_info *c)
>       c->double_hash = !!(sup_flags & UBIFS_FLG_DOUBLE_HASH);
>       c->encrypted = !!(sup_flags & UBIFS_FLG_ENCRYPTION);
>  
> +     if ((sup_flags & ~UBIFS_FLG_MASK) != 0) {
> +             ubifs_err(c, "Unknown feature flags found: %#x",
> +                       sup_flags & ~UBIFS_FLG_MASK);
> +             err = -EINVAL;
> +             goto out;
> +     }
> +
>  #ifndef CONFIG_UBIFS_FS_ENCRYPTION
>       if (c->encrypted) {
>               ubifs_err(c, "file system contains encrypted files but UBIFS"
> diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
> index bdc7935a5e41..e8c23c9d4f4a 100644
> --- a/fs/ubifs/ubifs-media.h
> +++ b/fs/ubifs/ubifs-media.h
> @@ -46,7 +46,7 @@
>   * UBIFS went into mainline kernel with format version 4. The older formats
>   * were development formats.
>   */
> -#define UBIFS_FORMAT_VERSION 4
> +#define UBIFS_FORMAT_VERSION 5

Alex Cope is working on a fix for file name encryption in ext4 so that
common plaintext prefixes don't result in common ciphertext prefixes.
Older kernels will not be able to read the new file names.

>  
>  /*
>   * Read-only compatibility version. If the UBIFS format is changed, older 
> UBIFS
> @@ -429,6 +429,8 @@ enum {
>       UBIFS_FLG_ENCRYPTION = 0x10,
>  };
>  
> +#define UBIFS_FLG_MASK 
> (UBIFS_FLG_BIGLPT|UBIFS_FLG_SPACE_FIXUP|UBIFS_FLG_DOUBLE_HASH|UBIFS_FLG_ENCRYPTION)
> +
>  /**
>   * struct ubifs_ch - common header node.
>   * @magic: UBIFS node magic number (%UBIFS_NODE_MAGIC)
> -- 
> 2.7.3
> 
> --
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