linux-kernel - RE: [PATCH v3] exfat: integrates dir-entry getting and validation

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Date:   Wed, 26 Aug 2020 13:19:09 +0900
From:   "Namjae Jeon" <namjae.jeon@...sung.com>
To:     "'Tetsuhiro Kohada'" <kohada.t2@...il.com>
Cc:     <kohada.tetsuhiro@...mitsubishielectric.co.jp>,
        <mori.takahiro@...mitsubishielectric.co.jp>,
        <motai.hirotaka@...mitsubishielectric.co.jp>,
        "'Sungjong Seo'" <sj1557.seo@...sung.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3] exfat: integrates dir-entry getting and validation

> 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.
> 
> 
> BR
> ---
> Tetsuhiro Kohada <kohada.t2@...il.com>
> >