Re: [PATCH 1/2] exfat: add NameLength check when extracting name

Tetsuhiro Kohada
2020-08-12T15:05:04Z

Thank you for your reply.

>> -static void exfat_get_uniname_from_ext_entry(struct super_block *sb,
>> - struct exfat_chain *p_dir, int entry, unsigned short *uniname)
>> +static int exfat_get_uniname_from_name_entries(struct exfat_entry_set_cache *es,
>> + struct exfat_uni_name *uniname)
>> {
>> - int i;
>> - struct exfat_entry_set_cache *es;
>> + int n, l, i;
>> struct exfat_dentry *ep;
>>
>> - es = exfat_get_dentry_set(sb, p_dir, entry, ES_ALL_ENTRIES);
>> - if (!es)
>> - return;
>> + uniname->name_len = es->de_stream->name_len;
>> + if (uniname->name_len == 0)
>> + return -EIO;
> Can we validate ->name_len and name entry ->type in exfat_get_dentry_set() ?

Yes.
As I wrote in a previous email, entry type validation, name-length validation, and name
extraction should not be separated, so implement all of these in exfat_get_dentry_set().
It can be easily implemented by adding uniname to exfat_entry_set_cache and calling
exfat_get_uniname_from_name_entries() from exfat_get_dentry_set().

However, that would be over-implementation.
Not all callers of exfat_get_dentry_set() need a name.
It is enough to validate the name when it is needed.
This is a file-system driver, not fsck.
Validation is possible in exfat_get_dentry_set(), but unnecessary.

Why do you want to validate the name in exfat_get_dentry_set()?

BR
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Tetsuhiro Kohada <kohada.t2@gmail.com>