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

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Date: Mon, 03 Jun 2024 10:50:51 -0400
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: <lkp@...el.com>,  <coreteam@...filter.org>,  <davem@...emloft.net>,
  <ebiggers@...nel.org>,  <fw@...len.de>,  <jaegeuk@...nel.org>,
  <kadlec@...filter.org>,  <kuba@...nel.org>,
  <linux-fscrypt@...r.kernel.org>,  <linux-kernel@...r.kernel.org>,
  <llvm@...ts.linux.dev>,  <netdev@...r.kernel.org>,
  <netfilter-devel@...r.kernel.org>,  <oe-kbuild-all@...ts.linux.dev>,
  <pablo@...filter.org>,
  <syzbot+340581ba9dceb7e06fb3@...kaller.appspotmail.com>,
  <syzkaller-bugs@...glegroups.com>,  <tytso@....edu>,
  <adilger.kernel@...ger.ca>,  <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH V5] ext4: check hash version and filesystem casefolded
 consistent

Lizhi Xu <lizhi.xu@...driver.com> writes:

> When mounting the ext4 filesystem, if the hash version and casefolded are not
> consistent, exit the mounting.
>
> Reported-by: syzbot+340581ba9dceb7e06fb3@...kaller.appspotmail.com
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> ---
>  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