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

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Date:	Mon, 26 Jan 2009 13:32:03 +0100
From:	Jan Kara <jack@...e.cz>
To:	Manish Katiyar <mkatiyar@...il.com>
Cc:	Eric Sandeen <sandeen@...hat.com>,
	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.

> 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.
  Well, I think ext2 with quotas is not used very often. But also note
that if a random garbage is passed in it has high chances that maxblocks
is >= 1. And that is all what is needed for ext2_get_blocks() to return
what we want.

								Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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