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

Namjae Jeon
2020-08-13T02:53:13Z

> 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().
No, We can check stream->name_len and name entry type in exfat_get_dentry_set().
And you are already checking entry type with TYPE_SECONDARY in
exfat_get_dentry_set(). Why do we have to check twice?

>
> However, that would be over-implementation.
> Not all callers of exfat_get_dentry_set() need a name.
Where? It will not checked with ES_2_ENTRIES.

> It is enough to validate the name when it is needed.
> This is a file-system driver, not fsck.
Sorry, I don't understand what you are talking about. If there is a problem
in ondisk-metadata, Filesystem should return error.

> Validation is possible in exfat_get_dentry_set(), but unnecessary.
>
> Why do you want to validate the name in exfat_get_dentry_set()?
exfat_get_dentry_set validates file, stream entry. And you are trying to check
name entries with type_secondary. In addition, trying add the checksum check.
Conversely, Why would you want to add those checks to exfat_get_dentry_set()?
Why do we check only name entries separately? Aren't you intent to return
validated entry set in exfat_get_dentry_set()?
>
>
> BR
> ---
> Tetsuhiro Kohada <kohada.t2@gmail.com>