linux-ext4 - Re: [PATCH] : make sure the buffer head members are zeroed out before using them.

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Message-ID: <497C9B03.4080008@redhat.com>
Date:	Sun, 25 Jan 2009 11:01:55 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Manish Katiyar <mkatiyar@...il.com>
CC:	ext4 <linux-ext4@...r.kernel.org>, "Theodore Ts'o" <tytso@....edu>,
	cmm@...ibm.com
Subject: Re: [PATCH] : make sure the buffer head members are zeroed out before
 	using them.

Manish Katiyar wrote:
> On Sun, Jan 25, 2009 at 9:45 PM, Eric Sandeen <sandeen@...hat.com> wrote:
>> Manish Katiyar wrote:
>>> On Tue, Jan 20, 2009 at 10:36 PM, Manish Katiyar <mkatiyar@...il.com> wrote:
>>>> ext2_quota_read doesn't bzeroes tmp_bh before calling ext2_get_block()
>>>> where we access the b_size of it. Since it is a local variable it
>>>> might contain some garbage. Make sure it is filled with zero before
>>>> passing.
>>> Hi Ted/mingming,
>>>
>>> Any feedback on this ??
>> This looks ok to me, Manish.  I'm curious, did you see this fail in real
>> life, and if so, what'd the failure look like?
> 
> Actually no......I realised this while going through the code. I was
> also wondering why we haven't hit this till now. Since ext{3,4} don't
> have this issue, the only reason I can think of is because ext2 with
> quota is not very much used or somehow we are lucky.
> 
>> With the change, the tmp_bh bh_size is 0, so maxblocks down the
>> get_block path is also 0, but I guess that works out ok.
> 
> Yes, but that is better than having a random garbage. Isn't it ?

Absolutely; it just struck me as a little odd but it's exactly what
__ext2_get_block does as well, I probably just need to take a closer
look at what it does w/ a 0 max.

-Eric

> Thanks -
> Manish

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