Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Gabriel Krisman Bertazi]

Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx> writes:

> When mounting the ext4 filesystem, if the hash version and casefolded are not
> consistent, exit the mounting.
>
> Reported-by: syzbot+340581ba9dceb7e06fb3@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
> ---
>  fs/ext4/super.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index c682fb927b64..0ad326504c50 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>  		goto failed_mount;
>  
>  	ext4_hash_info_init(sb);
> +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
> +	    !ext4_has_feature_casefold(sb)) {

Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
it was used solely for directories where ext4_hash_in_dirent(inode) is
true.

If this is only for the case of a superblock corruption, perhaps we
should always reject the mount, whether casefold is enabled or not?

-- 
Gabriel Krisman Bertazi