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

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Date:   Wed, 26 Aug 2020 11:56:22 +0900
From:   Tetsuhiro Kohada <kohada.t2@...il.com>
To:     Namjae Jeon <namjae.jeon@...sung.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?


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