Re: [PATCH v3] exfat: integrates dir-entry getting and validation

[Tetsuhiro Kohada]

Thank you for quick reply!

On 2020/08/26 13:19, Namjae Jeon wrote:
> > On 2020/08/26 10:03, Namjae Jeon wrote:
> > > > Second: Range validation and type validation should not be separated.
> > > > When I started making this patch, I intended to add only range validation.
> > > > However, after the caller gets the ep, the type validation follows.
> > > > Get ep, null check of ep (= range verification), type verification is a series of procedures.
> > > > There would be no reason to keep them independent anymore.
> > > > Range and type validation is enforced when the caller uses ep.
> > > You can add a validate flags as argument of exfat_get_dentry_set(), e.g. none, basic and strict.
> > > none : only range validation.
> > > basic : range + type validation.
> > > strict : range + type + checksum and name length, etc.
> >
> > Currently, various types of verification will not be needed.
> > Let's add it when we need it.
> > > > > -	/* validiate cached dentries */
> > > > > -	for (i = 1; i < num_entries; i++) {
> > > > > -		ep = exfat_get_dentry_cached(es, i);
> > > > > -		if (!exfat_validate_entry(exfat_get_entry_type(ep), &mode))
> > > > > +	ep = exfat_get_dentry_cached(es, ENTRY_STREAM);
> > > > > +	if (!ep || ep->type != EXFAT_STREAM)
> > > > > +		goto free_es;
> > > > > +	es->de[ENTRY_STREAM] = ep;
> > > >
> > > > The value contained in stream-ext dir-entry should not be used before validating the EntrySet
> > checksum.
> > > > So I would insert EntrySet checksum validation here.
> > > > In that case, the checksum verification loop would be followed by the
> > > > TYPE_NAME verification loop, can you acceptable?
> > > Yes. That would be great.
> >
> > OK.
> > I'll add TYPE_NAME verification after checksum verification, in next patch.
> > However, I think it is enough to validate TYPE_NAME when extracting name.
> > Could you please tell me why you think you need TYPE_NAME validation here?
> I've told you on previous mail. This function should return validated dentry set after checking
> file->stream->name in sequence.

Yes. I understand that the current implementation checks in that order.
Sorry, my question was unclear.
Why do you think you should leave the TYPE_NAME validation in this function?
What kind of problem are you worried about if this function does not validate TYPE_NAME?
(for preserve the current behavior?)

Don't worry, I will add TYPE_NAME verification to the v4 patch.
I will post it later today.

BR
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Tetsuhiro Kohada <kohada.t2@xxxxxxxxx>