Re: [PATCH v6 01/10] libfs: Create the helper function generic_ci_validate_strict_name()

[Gabriel Krisman Bertazi]

André Almeida <andrealmeid@xxxxxxxxxx> writes:

> +static inline 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);

There is something fishy here.  Concerningly, the fstests test doesn't
catch it.

utf8_validate is defined as:

  int utf8_validate(const struct unicode_map *um, const struct qstr *str)

Which returns 0 on success and !0 on error. Thus, when casting to bool,
the return code should be negated.

But generic/556 doesn't fail. That's because we are over cautious, and
also check the string at the end of generic_ci_d_hash.  So we never
really reach utf8_validate in the tested case.

But if you comment the final if in generic_ci_d_hash, you'll see this
patchset regresses the fstests case generic/556 over ext4.

We really need the check in both places, though.  We don't want to rely
on the behavior of generic_ci_d_hash to block invalid filenames, as that
might change.

-- 
Gabriel Krisman Bertazi