Re: [PATCH v7 6/8] f2fs: Handle casefolding with Encryption

From: Eric Biggers <ebiggers@kernel.org>
To: Daniel Rosenberg <drosen@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
	linux-ext4@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
	Chao Yu <chao@kernel.org>,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-fscrypt@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Richard Weinberger <richard@nod.at>,
	linux-mtd@lists.infradead.org,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	kernel-team@android.com
Subject: Re: [PATCH v7 6/8] f2fs: Handle casefolding with Encryption
Date: Tue, 11 Feb 2020 21:47:20 -0800	[thread overview]
Message-ID: <20200212054720.GH870@sol.localdomain> (raw)
In-Reply-To: <20200208013552.241832-7-drosen@google.com>

On Fri, Feb 07, 2020 at 05:35:50PM -0800, Daniel Rosenberg wrote:
> @@ -173,24 +193,24 @@ static inline bool f2fs_match_name(struct f2fs_dentry_ptr *d,
>  {
>  #ifdef CONFIG_UNICODE
>  	struct inode *parent = d->inode;
> -	struct super_block *sb = parent->i_sb;
> -	struct qstr entry;
> +	unsigned char *name;
> +	int len;
>  #endif
>  
>  	if (de->hash_code != namehash)
>  		return false;
>  
>  #ifdef CONFIG_UNICODE
> -	entry.name = d->filename[bit_pos];
> -	entry.len = de->name_len;
> +	name = d->filename[bit_pos];
> +	len = de->name_len;

This is missing le16_to_cpu().

>  int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
>  				const struct qstr *orig_name,
> +				f2fs_hash_t dentry_hash,
>  				struct inode *inode, nid_t ino, umode_t mode)
>  {
>  	unsigned int bit_pos;
>  	unsigned int level;
>  	unsigned int current_depth;
>  	unsigned long bidx, block;
> -	f2fs_hash_t dentry_hash;
>  	unsigned int nbucket, nblock;
>  	struct page *dentry_page = NULL;
>  	struct f2fs_dentry_block *dentry_blk = NULL;
> @@ -632,7 +652,6 @@ int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
>  
>  	level = 0;
>  	slots = GET_DENTRY_SLOTS(new_name->len);
> -	dentry_hash = f2fs_dentry_hash(dir, new_name, NULL);

Why was the call to f2fs_dentry_hash() moved to the caller, but for
f2fs_add_inline_entry() a different approach was taken?

> @@ -718,17 +737,19 @@ int f2fs_add_dentry(struct inode *dir, struct fscrypt_name *fname,
>  				struct inode *inode, nid_t ino, umode_t mode)
>  {
>  	struct qstr new_name;
> +	f2fs_hash_t dentry_hash;
>  	int err = -EAGAIN;
>  
>  	new_name.name = fname_name(fname);
>  	new_name.len = fname_len(fname);
>  
>  	if (f2fs_has_inline_dentry(dir))
> -		err = f2fs_add_inline_entry(dir, &new_name, fname->usr_fname,
> +		err = f2fs_add_inline_entry(dir, &new_name, fname,
>  							inode, ino, mode);

I'm really confused.  Why are you passing around both new_name and fname?
We already have new_name == fname.disk_name.  So isn't just the
'struct fscrypt_name' sufficient?

> +static f2fs_hash_t __f2fs_dentry_hash(const struct inode *dir,
> +				const struct qstr *name_info,
> +				const struct fscrypt_name *fname)
>  {
>  	__u32 hash;
>  	f2fs_hash_t f2fs_hash;
> @@ -85,6 +86,11 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
>  	if (is_dot_dotdot(name_info))
>  		return 0;
>  
> +	if (IS_CASEFOLDED(dir) && IS_ENCRYPTED(dir)) {
> +		f2fs_hash = fscrypt_fname_siphash(dir, name_info);
> +		return f2fs_hash;
> +	}

This is missing cpu_to_le32().

Also, above we have:

        /* encrypted bigname case */
        if (fname && !fname->disk_name.name)
                return cpu_to_le32(fname->hash);

That won't work with encrypted+casefolded directories without the key, because
now sometimes the hash from the no-key name is needed even when the disk_name is
available.  This will cause a crash in fscrypt_fname_siphash() being called
without the key.  I think you want:

        if (fname && fname->is_ciphertext_name)
                return cpu_to_le32(fname->hash);

Can you please write xfstests for encrypt+casefold?

- Eric