Eric Biggers <ebiggers@xxxxxxxxxx> writes:
> On Wed, May 18, 2022 at 01:23:16PM -0400, Gabriel Krisman Bertazi wrote:
>> Instead of reimplementing ext4_match_ci, use the new libfs helper.
>>
>> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>> ---
> [...]
>> int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
>> struct ext4_filename *name)
>> {
>> @@ -1432,20 +1380,25 @@ static bool ext4_match(struct inode *parent,
>> #if IS_ENABLED(CONFIG_UNICODE)
>> if (parent->i_sb->s_encoding && IS_CASEFOLDED(parent) &&
>> (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
>> - if (fname->cf_name.name) {
>> - if (IS_ENCRYPTED(parent)) {
>> - if (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
>> - fname->hinfo.minor_hash !=
>> - EXT4_DIRENT_MINOR_HASH(de)) {
>> + int ret;
>>
>> - return false;
>> - }
>> - }
>> - return !ext4_ci_compare(parent, &fname->cf_name,
>> - de->name, de->name_len, true);
>> + if (IS_ENCRYPTED(parent) &&
>> + (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
>> + fname->hinfo.minor_hash != EXT4_DIRENT_MINOR_HASH(de)))
>> + return false;
>> +
>> + ret = generic_ci_match(parent, fname->usr_fname,
>> + &fname->cf_name, de->name,
>> + de->name_len);
>> + if (ret < 0) {
>> + /*
>> + * Treat comparison errors as not a match. The
>> + * only case where it happens is on a disk
>> + * corruption or ENOMEM.
>> + */
>> + return false;
>> }
>> - return !ext4_ci_compare(parent, fname->usr_fname, de->name,
>> - de->name_len, false);
>> + return ret;
>> }
>
> This needs an explanation for why it's okay to remove
> 'fname->cf_name.name != NULL' from the condition for doing the hash comparison
> for an encrypted+casefolded directory entry.
Hi Eric,
The reason is that the only two ways for fname->cf_name to be NULL on a
case-insensitive lookup is 1) if name under lookup has an invalid
encoding and the FS is not in strict mode; or 2) if the directory is
encrypted and we don't have the key. For case 1, it doesn't
matter, because the lookup hash will be generated with fname->usr_name,
the same as the disk (fallback to invalid encoding behavior on !strict
mode). Case 2 is caught by the previous check
(!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent)), so we
never reach this code.
I'll add the above rationale to the commit message.
--
Gabriel Krisman Bertazi
