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Re: [Qemu-devel] remark about http://www.freeoszoo.org
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] remark about http://www.freeoszoo.org |
Date: |
Mon, 4 Oct 2004 12:43:42 +0100 |
User-agent: |
KMail/1.7 |
On Monday 04 October 2004 12:29, Lennert Buytenhek wrote:
> On Mon, Oct 04, 2004 at 02:50:31AM -0400, Karl Magdsick wrote:
> > Free OS Zoo suggests using dd with the seek= option in the _specific_
> > case of Linux, which appears to be safe. My comment was explicitly a
> > note of caution in the _general_ case.
>
> Yep. As well as:
>
> "[...] the image will likely contain parts of deleted files from
> the host OS."
>
> Just curious, do you have an example of any such system where this
> would be the case? I don't know of any system that doesn't support
> sparse files and doesn't pad out the file with zeroes if you
> truncate(2) it to be bigger.
I'm fairly sure any half-sane OS will zero the "sparse" bits of a file on
allocation. IIRC even Windows NT does zero the sparse bits of a file.
Failure to do so would be a rather large security hole, effectively allowing
unprivileged users to read privileged data.
IMHO the original post is unjustified paranoia, rather than reasonable
caution.
Paul