Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx> writes:
> From: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>
> generic_ci_match can be used by case-insensitive filesystems to compare
> strings under lookup with dirents in a case-insensitive way. This
> function is currently reimplemented by each filesystem supporting
> casefolding, so this reduces code duplication in filesystem-specific
> code.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> [eugen.hristev@xxxxxxxxxxxxx: rework to first test the exact match, cleanup
> and add error message]
> Signed-off-by: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx>
Other than the origin of the length in memcmp mentioned by Eric, this patch
looks good to me now.
Thanks again for picking up this work!
> ---
> fs/libfs.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 4 +++
> 2 files changed, 78 insertions(+)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index b635ee5adbcc..6a6cfa2d7d93 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -1854,6 +1854,80 @@ static const struct dentry_operations generic_ci_dentry_ops = {
> .d_revalidate = fscrypt_d_revalidate,
> #endif
> };
> +
> +/**
> + * generic_ci_match() - Match a name (case-insensitively) with a dirent.
> + * This is a filesystem helper for comparison with directory entries.
> + * generic_ci_d_compare should be used in VFS' ->d_compare instead.
> + *
> + * @parent: Inode of the parent of the dirent under comparison
> + * @name: name under lookup.
> + * @folded_name: Optional pre-folded name under lookup
> + * @de_name: Dirent name.
> + * @de_name_len: dirent name length.
> + *
> + * Test whether a case-insensitive directory entry matches the filename
> + * being searched. If @folded_name is provided, it is used instead of
> + * recalculating the casefold of @name.
> + *
> + * Return: > 0 if the directory entry matches, 0 if it doesn't match, or
> + * < 0 on error.
> + */
> +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)
> +{
> + const struct super_block *sb = parent->i_sb;
> + const struct unicode_map *um = sb->s_encoding;
> + struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
> + struct qstr dirent = QSTR_INIT(de_name, de_name_len);
> + int res = 0;
> +
> + if (IS_ENCRYPTED(parent)) {
> + const struct fscrypt_str encrypted_name =
> + FSTR_INIT((u8 *) de_name, de_name_len);
> +
> + if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
> + return -EINVAL;
> +
> + decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
> + if (!decrypted_name.name)
> + return -ENOMEM;
> + res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
> + &decrypted_name);
> + if (res < 0) {
> + kfree(decrypted_name.name);
> + return res;
> + }
> + dirent.name = decrypted_name.name;
> + dirent.len = decrypted_name.len;
> + }
> +
> + /*
> + * Attempt a case-sensitive match first. It is cheaper and
> + * should cover most lookups, including all the sane
> + * applications that expect a case-sensitive filesystem.
> + */
> +
> + if (dirent.len == (folded_name->name ? folded_name->len : name->len) &&
> + !memcmp(name->name, dirent.name, dirent.len))
> + goto out;
> +
> + if (folded_name->name)
> + res = utf8_strncasecmp_folded(um, folded_name, &dirent);
> + else
> + res = utf8_strncasecmp(um, name, &dirent);
> +
> +out:
> + kfree(decrypted_name.name);
> + if (res < 0 && sb_has_strict_encoding(sb)) {
> + pr_err_ratelimited("Directory contains filename that is invalid UTF-8");
> + return 0;
> + }
> + return !res;
> +}
> +EXPORT_SYMBOL(generic_ci_match);
> #endif
>
> #ifdef CONFIG_FS_ENCRYPTION
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 639885621608..f8ca264a0edc 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3367,6 +3367,10 @@ extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
> extern int generic_check_addressable(unsigned, u64);
>
> extern void generic_set_sb_d_ops(struct super_block *sb);
> +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);
>
> static inline bool sb_has_encoding(const struct super_block *sb)
> {
--
Gabriel Krisman Bertazi
