linux-kernel - Re: [PATCH v4 01/10] libfs: Create the helper function generic_ci_validate_strict

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Message-ID: <87a5gck7i1.fsf@mailhost.krisman.be>
Date: Thu, 12 Sep 2024 15:16:22 -0400
From: Gabriel Krisman Bertazi <gabriel@...sman.be>
To: André Almeida <andrealmeid@...lia.com>
Cc: Hugh Dickins <hughd@...gle.com>,  Andrew Morton
 <akpm@...ux-foundation.org>,  Alexander Viro <viro@...iv.linux.org.uk>,
  Christian Brauner <brauner@...nel.org>,  Jan Kara <jack@...e.cz>,
  linux-mm@...ck.org,  linux-kernel@...r.kernel.org,
  linux-fsdevel@...r.kernel.org,  kernel-dev@...lia.com,  Daniel Rosenberg
 <drosen@...gle.com>,  smcv@...labora.com,  Christoph Hellwig <hch@....de>,
  Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v4 01/10] libfs: Create the helper function
 generic_ci_validate_strict_name()

André Almeida <andrealmeid@...lia.com> writes:

> Create a helper function for filesystems do the checks required for
> casefold directories and strict encoding.
>
> Suggested-by: Gabriel Krisman Bertazi <gabriel@...sman.be>
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
> Changes from v2:
> - Moved function to libfs and adpated its name
> - Wrapped at 72 chars column
> - Decomposed the big if (...) to be more clear
> ---
>  fs/libfs.c         | 38 ++++++++++++++++++++++++++++++++++++++
>  include/linux/fs.h |  1 +
>  2 files changed, 39 insertions(+)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 8aa34870449f..99fb36b48708 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -1928,6 +1928,44 @@ int generic_ci_match(const struct inode *parent,
>  	return !res;
>  }
>  EXPORT_SYMBOL(generic_ci_match);
> +
> +/**
> + * generic_ci_validate_strict_name - Check if a given name is suitable
> + * for a directory
> + *
> + * This functions checks if the proposed filename is valid for the
> + * parent directory. That means that only valid UTF-8 filenames will be
> + * accepted for casefold directories from filesystems created with the
> + * strict encoding flag.  That also means that any name will be
> + * accepted for directories that doesn't have casefold enabled, or
> + * aren't being strict with the encoding.
> + *
> + * @dir: inode of the directory where the new file will be created
> + * @name: name of the new file
> + *
> + * Return:
> + * * True if the filename is suitable for this directory. It can be
> + * true if a given name is not suitable for a strict encoding
> + * directory, but the directory being used isn't strict
> + * * False if the filename isn't suitable for this directory. This only
> + * happens when a directory is casefolded and the filesystem is strict
> + * about its encoding.
> + */
> +bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name)
> +{
> +	if (!IS_CASEFOLDED(dir) || !sb_has_strict_encoding(dir->i_sb))
> +		return true;
> +
> +	/*
> +	 * A casefold dir must have a encoding set, unless the filesystem
> +	 * is corrupted
> +	 */
> +	if (WARN_ON_ONCE(!dir->i_sb->s_encoding))
> +		return true;
> +
> +	return utf8_validate(dir->i_sb->s_encoding, name);
> +}
> +EXPORT_SYMBOL(generic_ci_validate_strict_name);
>  #endif
>  
>  #ifdef CONFIG_FS_ENCRYPTION
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index fd34b5755c0b..937142950dfe 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3385,6 +3385,7 @@ extern int generic_ci_match(const struct inode *parent,
>  			    const struct qstr *name,
>  			    const struct qstr *folded_name,
>  			    const u8 *de_name, u32 de_name_len);
> +bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name);

As mentioned in the other patch, please make this an inline helper.  But
also, the declaration needs to be guarded by CONFIG_UNICODE.

>  
>  static inline bool sb_has_encoding(const struct super_block *sb)
>  {

-- 
Gabriel Krisman Bertazi