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Re: XFS information leak during crash

To: Jan Kasprzak <kas@xxxxxxxxxx>
Subject: Re: XFS information leak during crash
From: Nathan Scott <nathans@xxxxxxx>
Date: Thu, 3 Nov 2005 10:49:56 +1100
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-xfs@xxxxxxxxxxx
In-reply-to: <20051102233629.GD6759@fi.muni.cz>; from kas@fi.muni.cz on Thu, Nov 03, 2005 at 12:36:29AM +0100
References: <20051102212722.GC6759@fi.muni.cz> <20051103101107.O6239737@wobbly.melbourne.sgi.com> <20051102233629.GD6759@fi.muni.cz>
Sender: linux-xfs-bounce@xxxxxxxxxxx
User-agent: Mutt/1.2.5i
On Thu, Nov 03, 2005 at 12:36:29AM +0100, Jan Kasprzak wrote:
> ...
>       Yes, of course. However, the issue is probably much worse
> on XFS, because on XFS it probably affects not only the files being
> created/extended, but also the files being rewritten. Most other

No, thats not correct - XFS behaves as most filesystems do and
will write over the top of existing data.

> filesystems rewrite the files in-place, so when you rewrite the file,
> even with data=writeback you get only the mix of the old and new
> contents. Not somebody else's random data.

XFS also rewrites files in-place.  You will never get someone else's
current data (that would be metadata corruption...), it would only
ever be uninitialised, previously-free space.  But as I said, other
filesystems have the same window in which this can happen (in the
absence of stronger data ordering/journalling semantics, of course).

cheers.

-- 
Nathan


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