linux-kernel - Re: [PATCH] fat: Read buffer overflow

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Date:	Sat, 08 Aug 2009 19:18:01 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Roel Kluin <roel.kluin@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fat: Read buffer overflow

OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> writes:

> Pekka Enberg <penberg@...helsinki.fi> writes:
>
>> Yes, but we pass "ulen" to vfat_is_used_badchars(). The value of
>> "ulen" is a returned in the "longlen" argument of xlate_to_uni() which
>> in turn is calculated as follows for the UTF-8 case:
>>
>>   int name_len = strlen(name);
>>   *outlen = utf8s_to_utf16s(name, PATH_MAX, (wchar_t *) outname);
>>   *outlen -= (name_len - len);
>>   *longlen = *outlen;
>>
>> Maybe "*outlen" can never be negative because of some invariants that
>> I don't see but it's so non-obvious to me that I'd like to see the
>> explicit check in vfat_is_used_badchars().
>
> Ah, good point. Sorry, I was looking my tree. I'm going to submit the
> attached patch on next merge window.
>
> Is this enough for it?

BTW, if we want the sanity check of "longlen", I'd like to put it in the
end of xlate_to_uni(), not vfat_is_used_badchars(). Because I think it's
job of xlate_to_uni().

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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